Recumbant Mid-Drive Scrapbuilt Buildlog. Pics & Questions.

[MattsAwesomeStuff]

Hi everyone, I'm new here. I'm building my first bike.

Briefly, my background is more entry-level electric stuff, not bicycle stuff. I don't know how to build a bike. I don't know how to repair a bike. I might be able to take apart a bike. I can barely ride a bike. And I want to build a recumbent which, I can't actually say I've ever ridden or even seen one of in person. So I'll have a lot of bicycle questions. My bike terminology is lacking. If you'd like to take the time to correct me and explain what is what, I'd appreciate that. Bear with me.

I've done a lot of research, reading, planning and pondering before now so as to not waste everyone's time and keep this thread at least semi-fun with some pics. First post here is going to be a data dump of all the specs so far. Hopefully it gets better from then on.

First up, I'm cheap. I'm interested in building as much from scrap as possible. I also find this intellectually/artistically fun, when the answer to everything becomes "just buy this" or "just spend more" the answer might as well be "just go buy one, don't bother building one" which is a half step away from "just buy a nice car." Please frame any commentary directed at me within this context. Hopefully my choices are at least interesting, if not optimal.

Here we go.

---

Structure:

There are so many recumbent design options I hit paralysis by analysis for a while. Maybe those of you reading this aren't too familiar with recumbents either, so after reading for a couple days I picked from a few hundred samples and condensed the major design choices to these things. I've labelled them myself, some of the terms might be wrong as I just made them up:

- I will be choosing to build a a Short Wheelbase. I'm not entirely sure what a racer is, but something that looks like a mid or high racer probably? Not too low for 4 reasons: 1- I'm scared to be too low, dangerous in traffic, 2- I don't want to ride with my chin down, opposite reason I don't like uprights cranking my chin up to see the road, 3- I like to be high enough to enjoy the view, I would like to tour with this bike (will also be using it in the city). 4- It's not comfortable to be in a sky-crawling position. -- I am aware there is a drag penalty for every inch of height I refuse to abandon, I accept the tradeoff --
- Straight or S-Pipe frame, diamond is ugly.
- Above seat steering, probably. Simpler.
- RWD & Right-side drive. I want to use at least the rear cassette to give some mechanical motor gearing (chain issues though?), I might not need it since I first chose this.
- 26" rear, 20" front. I think this makes it easier to have lower posture with an upright seat and cargo room.
- Front suspension from a kid's bike (bad idea?)
- Rear suspension maybe, if I can figure it out.

Battery

I plan on using Lithium-Ion batteries from laptop battery packs that I'll (hope to) get from a computer recycler for free/volunteer time. 18650s. Yes, I know this is a panty-twirling trigger for some well-known community participants here. The project becomes non-interesting to me if I have to buy batteries, so I am fixed in this choice. I built myself a spot welder (for free) to weld the tabs. I know not to charge if sunk below 2.7v. I know to see what reaches what voltage and what holds it there. I know to set up drain-tests and discard crap cells.

I haven't yet, but I'll build (for free) a 4.2V, 400A charger to charge/test mass packs in a half hour sometime when I've got time.

More battery details later on.

Motor:

I have a few motors to choose from. I selected this 30lb treadmill brush motor. I am aware the idea of this is akin to ramming a cactus up the least comfortable place imaginable for some active participants here, but it's what I've chosen because it was free (maybe $1). It's not even a nice brush motor with neodymium magnets, they're ceramic. It's not even a 4-pole magnet. Hell, the magnets aren't even in good shape, one looks like it was cracked in half before it was assembled. Oh well. Here she is:

Oops not that one, that's way too small. Let's go bigger!:

That's more like it! Toss that flywheel (10lbs, down to 20lbs now). Let's take 'er apart for a looksie:

Okay, so it's not an ultra-light compact RC motor. But unless one of you are giving me one of those for $1, it's what I'm using. Speaking of RC motors, the end caps on this thing alone (1/2" steel) probably weigh as much as a whole RC motor:

Why is it almost as big as a 2L pop bottle and serviceable as a boat anchor? Well, 1/4" steel armor(?) plating for a case might have something to do with it:

Great. Except that it'll have to be sealed up better to weatherproof it, so I'll have to de-rate the motor by 3-4x without all that air cooling. Coincidence, that'll bring it down to to the 500W legal limit most places. *stamps* APPROVED!

Controller:

Not sure, will build it myself. I'll have to buy ~$25 of MOSFETs for it. Probably have most of the rest laying around.

Charger:

Wait, go back to those motor specs. Did that say 130VDC continuous, 150VDC for treadmill (peak power for minutes only) use? Hrm. An evil idea brews. Still in the concept stage, 'cept I'm pretty sure it'll work fine.

Out of your wall (north america) comes 120VAC. If you rectify this ($2 shipped, 15A rectifier) and smooth it with a sizable cap, you get 170VDC (because 120VAC actually peaks at 170V and the cap will surge-charge to that voltage). Okay, so the motor wire insulation isn't going to break down at 170V either. It might spin too fast (too fast for me to use it anyway, I don't need to pass cars on the highway), but I will have speed control anyway. Some PWM thing to chop up the 170V.

This means, no hauling a bulky transformer around. Just a power cord, rectifier (matchbox sized) and cap, built into the battery pack. Maybe an AC run cap to limit the current, (normal circuit allows 1800W flowrate before it trips the breaker), or I could use my controller in reverse (controls average current from 170VDC wall to 170VDC batteries, rather than 170VDC batteries to motor). It also means I can pirate charge a pack at breaker-friendly 1500W flow rate. Avast!

Okay, back up again. Batteries then need to be 170V. That's a string of about 42 in series. Pretty long. I figure, anywhere from 2-8 in parallel. Not sure if I'll parallel them all (better, auto-balancing) or into 2-3 strings (separate circuits, even faster charging since I'm limited by breakers).

Battery packs will be modular and removable anyway, so I can bring 'em into fast food places and charge while I eat on the road (look around next time you're in one, outlets everywhere).

Gearing:

It's a mid-drive right? Two problems. One, while this motor spins very slow compared to your RC whizzers, it's not slow enough yet. Worse, it's not even pointing in the right direction. I have to get this motor shaft sticking out sideways into the chain somewhere. But the motor is just way too fat to put it sideways especially after a gearbox. Belts are inefficient and annoying and have to be sized and tensioned and can break and you have to buy them and pulleys. Big bucket of nope all over the place.

First lemme address the speed thing. Ever take apart a cordless drill? Cheap ones have plastic/nylon gears. Good ones have tool steel gears with multi-stage planetary arrangements. Some even have a slow/fast mode by enabling a different planetary ring:

But y'know, cordless drills are like, a couple hundred watts, few minutes use at best. And have lifetimes of dozens of hours at best. Will those little metal gears hold up? Maybe not. Time to whip out the big guns. No more delicate japanese plastic frames. 1960s detroit steel:

Okay, so it's dirty, but it can be cleaned and re-greased. And run over by a bulldozer if I wanted. Here it is next to the baby:

38:1 geardown btw. Might be too much by the time I'm done, I might disengage one of the pair. Handy thing about these gearboxes is they have a chuck mounted to them, making quick prototypes easy to mount (no couplers, just use the chuck).

Moving onto the second gearing problem. 90 degrees. Well, I had a funny idea. Ever seen an eggbeater-style 1800s hand drill? 90-degree bevel gears. Attached to a 500RPM cordless drill, it rotates the handle at a perfect biking cadence. Both have chucks, so grab a bar, and you've got a 10-second e-bike:

Fine, it's not really powerful enough to drive a bike, makes for a fun demo though. Option A is going with a $10 right-angle (electricians) drill adapter. But they often have nylon gears and probably won't hold up either. Option B then, is to have a friend willing to send you the gearbox from a tiny 1.5Hp trolling motor. The propeller has to turn at 90 degrees to the motor shaft. Constantly. Has to be sealed. Sounds perfect! Sometimes they're even geared down:

Misc:

Cargo rack. Mount the batteries under it. Fenders. Paniers I'll probably make myself. Brake lights, riding lights, turning lights.

Power Requirements:

Warning this'll get boring, skip it if you want. It was hard to find calculations on this. 3 primary opposing forces on a bike:

#1 - Transmission resistance (gears, chain etc). Nearly negligible on a bike.
#2 - Rolling resistance. Something about tires squishing on the road. This increases by weight, (more weight more squish), but is generally fixed and somehow smaller on smaller diameter tires. Also smaller by narrower and smoother tires. It makes up a small amount (50W perhaps at slow speeds and doesn't increase much past that).
#3 - Wind resistance. This increases as a cube function of speed for power (twice as fast takes 8x as much power). So it increases a square of speed for distance or energy. (twice as fast takes 8x as much power, but you do still get there twice as fast so it's only 4x more energy). This dominates any power calcs any faster than granny speeds.

Hence, speed kills. I extrapolated on the basic cubic relationship presuming 100 watts and 25km/h speed for myself, until I found a calculator here that more or less told me the same thing but was fancier so I use that now. Recumbents are lower and thus have less air drag, so, in their case, speed only... wounds/cripples.

I want to use this bike for touring too. So, I want to carry as large a pack as possible (sometimes). Perhaps 2500Wh. Ignore any time anyone says "Ah". That number only matters when compared to identical voltages. Battery power is measured in watt hours (or joules, since "watt hour" is like saying you drove '30 feet per second hour", just say distance, but watt hour is a more usable concept).

2500Wh means I can charge (by the time I park) in about 2 hours liberally, without even splitting circuits. The math works out that there's almost zero difference when traveling at 32, 40, 45, or 50km/h. (20-30miles/hour). The faster speed drains energy at an accelerated rate, but it also gets me to a destination and charging sooner. They all equal out to ~30km/hr including charge time. So if I wanted to travel 600km in a (long) day, it would take me 20 hours no matter what speed I go. [This is coincidence!]

This presumes I pull over and charge anywhere when running out of juice. If it's longer between stops (desert towns), I can get much farther on one charge at a slow speed.

Energy (Battery) Requirements:

Ugg, let's just break up this wall of text with a picture of a battery:

And a picture of what's inside:

Easiest method for opening ultrasonic-welded plastic:
1 - Place case in vice, just above weld line.
2 - Crank until the plastic starts to buckle on the bottom.
3 - Tap along the edges with a hammer, watch it pop. Sometimes a chisel/screwdriver encourages it to pop, but you're not cutting through it, you're just stressing it.

Wash rinse repeat 50-100 more times I guess.

8-cell packs in a 42 string is 336 batteries. That's 2.5" tall, 6" wide, 24" long. A fair battery shelf on the cargo rack. I could re-arrange however.

It'll also give me about 80amps of current, or 13,600W of power on tap. Or, 18Hp. Enough to overdrive my motor for the ~200 seconds it could withstand the load before reaching critical temp and needing 7 minutes cooling.

That's everything I *do* know. Next up are the things I'm going to need help/suggestions with.

 

[MattsAwesomeStuff]

Human Power:

Okay, starting to get into the unknown.

Bike freewheels suck, so I've heard. I've read Atomic Zombie's (scroll down) tutorial on Freewheel disassembly. But I've never been able to identify what part comes off. Someone gave me another idea though. The ratchet or pawl style freewheels on bikes suck. A better kind is the traveling pin overrunning clutch. Looks like this:

You can buy them in standard bearing sizes I hear. Or, salvage them from starter motors. The wheel left of #2 below is the overrunning clutch:

I might buy a pair from somewhere, since even broken starters are worth a $20 core charge and hard to find if you're not a car person (I'm not).

Two counter-facing freewheels at the drive sprockets (behind/under the seat, half way between pedals and rear wheel) are somewhat important for two reasons:
1 - When batteries are dead, you don't want to have to crank the motor over.
2 - When lazy, you don't want to have to move your legs to keep up with the motor (bigwheels-trike style).

No one's really come up with a great solution for this. I'll have to eventually learn how to get a damned freewheel off and hope it works.

Frame:

Here are a few donor bikes I got for free/cheap:

I'll probably be using these two primarily. Red is a kids bike I chose because it has a 20" tire and some(?) front suspension. That was my entire selection process. REMINDER: I don't really know anything about bikes. The blue one is ancient and hopefully overbuilt. 3 rear dropouts:

I also can get whatever scrap metal I want. This stuff came from Awkward Unwanted Workout Machine Hell. Most of the box frames are 3/32" thick. Some 7/8", 1", 1.5" square, some 1.5"x7/8". I'll probably use the 1.5" box as the main straight pipe from seat to crank. I know it's not optimal, it's what I have.

Who loves measurements? Everyone:

I measured pixels on my screen with a ruler and determined that 47" between tire spots is a good(??) distance. Then I MSPainted this, to proper scale to help me visualize what to chop/add:

Seat height? Other considerations?

Suspension:

I guess I have front suspension now? Good enough?

Rear suspension, the little kids bike spring probably won't be enough? I think I'll have to move it. Rear suspension scares me because it stresses the chain, and I'd need to add chain tensioner thingies. In an upright the crank is before the pivot, on a recumbent, it's obviously after.

I think I'll mount the motor/gearbox to the frame, rear of whatever pivot I do have. But seat/batteries/cargo ahead of it. Should I try adding some angled front suspension (ala Amberwolf) rather than the little spring I have now?

Ideas?

Chain pathing:

Unforeseen challenges. Chain must clear from crank to rear wheels. Must cross above front forks or they'll hit it. Must go under seat to where it joins the motor. This is not a straight line. I'll need redirector things. Presumably extra rear-derailler-things (the preying-mantis arm parts) are okay for this? Might need beefier springs.

Ideas?

Steering:

There's a thing called tiller steering that is bad, where the fork angle doesn't point at the tire/road contact point, thus why most forks are curved forward to put the tire on that line? Major issue?

Brakes:

I forget the precise name of them, but the kind on the red bike that pull from the side. Disc brakes are probably a better idea, but, these are not free and I don't know how to add them. I can cut/work metal. Is this easy to do/add to the axle or not something you try on your own?

Regen braking would be nice, but it requires too many driveline complications so I think I'll have to say goodbye to that.

Battery Balancing:

Think I'll skip this, do it manually a few times a season. Crazy idea: somehow fab a 42-pole-double-throw switch to toggle the whole string from 8p x 42 in series (170V) to all 336 in parallel (4.2V). This will force all batteries to balance. Auto-trigger a solenoid to trigger this when stopped or braking.

Not sure I can pull it off.

Option #2 is no batteries will be hardwired. They'll be fitted on circuitboards with lever springs for every contact point. If I want to balance a pack, I slide the circuitboards out, flip them to their alternate side (alternate wiring) and slide them back into place, manually switching all 336 (or whatever multiple of 42 I settle on) from series to parallel. Worth doing for 10 minutes after every few charges.

...

When I actually get to building (soon), I'm sure I'll have a million pre-school-esque bicycle questions. I've read through all of Atomic Zombie's tutorials, but I have a feeling I'm going to need quite a bit of hand holding, if people could be so kind.

I'll also need to teach myself to weld. I built myself a TIG/Stick welder (for free), so ready to go on that front.

That's all for now. Feedback and criticism (within my context) mightily encouraged.

Data dump complete. Should be less boring from here out.

 

[CrazyJerry]

Mat,
Great job detailing all of your possibilities! You mentioned using an s-frame and you mentioned not especially liking the chin down position (opposite of the head wrenched backward when aero on a diamond frame). Went through this myself - but still wanted to be aero as much as I could be. With the addition of a small sponge at the headrest, the chin down is actually quite comfortable. This position was extremely relaxed for a 100 mile ride/race I did a couple of years ago. The handlebar mirrors allow for excellent visibility behind, and, I have never had any issues with "not being seen" due to its height. Wheels are 20" and I can reach down to the pavement and balance myself when stopped. Below are a few pics of my position.

If you look close, you can get ideas regarding the rear suspension/idler (you mentioned the possibility of a motor in that area but had questions about how rear suspension might affect the chain..) Although not an ebike, I used a gear cluster on top of the boom along with a Schlumpf to get about 175 gear inches which should take care of any cadence issues with high speed and the 20" wheels.

~CrazyJerry

 

[Warren]

Matt,

I have been building/modifying recumbents since the mid 1980's. The perfect electric assist recumbent, IMO, would run dual 26 inch wheels (huge selection of strong, aero wheels, disc brake compatible, many tire choices), cranks 6-9 inches above the seat, cranks right over the front axle, ~56" wheelbase. A dual 26" version of the Verano...basically a FF electric motorbike.

http://lightfootcycles.com/products-overview/bike-models-overview/verano/

Recumbents are perfect for electric assist. The main frame can be a single large tube containing the motor, battery, controller, charger. An aluminum fabricator can bend you up an 5" wide, 8" deep channel, or you can fab it up with thin sheet, aluminum angle, and SS pop rivets. Guys have done them with birch veneer, and spruce strips, kayak style. Attach rear chain stays, and steer tube, from a donor bike. Buy a real recumbent seat, and steerer from Bacchetta, RANS, etc.

Frankly, I can't believe somebody isn't already selling this rig. Liability, and limited market, I suppose.

Warren

 

[amberwolf]

For the moment, until I have time to fully read all of your post and reply, I'll just link you to my CrazyBike2's build thread
http://www.endless-sphere.com/forums/viewtopic.php?f=2&t=12500

and the older Electricle blog that contains my journey to getting it working as a middrive (it is now a hubmotor)
http://electricle.blogspot.com

and my new in-progress bike's build thread
http://endless-sphere.com/forums/viewtopic.php?t=31255&f=28#p452881

They may have some useful information for you.

 

[MattsAwesomeStuff]

I have never had any issues with "not being seen"

Well, #1 - I have heard many stories about low recumbents being invisible to cars, so, your opinion balances this in part but doesn't negate it.
#2 - My issue is less with me not being seen by others, than me being able to see. I am not interested in competition or racing. I do want to be able to see other vehicles, over hoods, as well as around at the scenery. Too low and even tall field grass blocks my view.

When I look at that second picture, I just don't like the look of the posture at all. Like I said, I'm aware there's tradeoffs for height, and I accept them. Difference strokes for different folks.

Gorgeous bike though. Looks great.

Thanks for the pics of the idler, ideas all help.

The perfect electric assist recumbent, IMO, would run dual 26 inch wheels

Why? I've heard (questionable) claims to the marginal benefits of small tires, but none for big. Also, without a smaller front wheel, I'll have posture problems without even getting the benefit of lowered height.

What's better about a 26" in front?

Buy a real recumbent seat, and steerer from Bacchetta, RANS, etc.

Buy? *spit*. MAKE.

The Verano isn't to my liking. Seat looks very similar to whoever did the Yellow Bike and wrote the tutorial for conduit-bent seat frame. Got some more ideas off it though, thanks.

For the moment, until I have time to fully read all of your post and reply, I'll just link you to my CrazyBike2's build thread

I've skimmed all these mentioned a couple times already. I like that you make things work rather than just buying something better. Threads have been too long/popular for me to read in detail, but, well, when you go back and re-read the start of this thread you'll note that I already mention an idea or two of yours by name.

It's an old post on your bog, but are you still without a welder? I can tell you how to make one for free from common junk.

 

[recumpence]

)Personally, I would go with a 20 inch front wheel for a number of reasons;

#1 A larger wheel puts the cranks really high off the ground. That makes the ground hard to reach when stopping.

#2 A smaller front wheel is generally stronger. My E-cumbent has a 20 inch front wheel and that wheel really takes a beating.

#3 The disc brake will have more power with a smaller front wheel.

Much of this is personal opinion, however.

Matt (the "Other" Matt :wink: )

 

[Warren]

other Matt,

Oh no! I forgot. You are one of the mid-western low racer crowd.

I spent years discussing this issue with you guys, on the old hpv list. I was "big wheels are better" Berger. Since those days, sales of high racers have out-numbered sales of low racers many times over. RAAM, crits, etc. have been won by high racers. High racers have gone from 559, and 571 wheels to mostly 622 wheels. Last time I will mention it.

Warren

 

[REdiculous]

Cool, another treadmill motor!

I'm NOT electrically inclined so I'm running my treadmill motor from an SCR controller which is plugged into a cheap inverter - less than ideal, but functional. My motor is mated to a pocket bike and I've documented it pushing 850w, which it's pulling from a 12v 50ah pack of SLAs. (that's my way of saying a high battery voltage isn't a strict requirement to make these motors work)


If you can come up w/ a better way to control the motor, though, for cheap or nearly-free, I might have to copy you. :wink:

 

[MattsAwesomeStuff]

Being the bike noob that I am, could someone help suggest me, based on my design:

1 - What the wheel-wheel (on ground contact) distance should be? ("wheelbase?") Is 47" good/bad/long/average/short?
2 - What a good ride height for the seat would be, assuming a natural posture?
3 - How thick my frame should be, if I'm using any of that square/box tubing I showed from the exercise machines. It's not fancy chromoly or anything, just plain mild steel. I have no idea whether a 0.75" square pipe at 1/16" thick would be enough, or whether it should be 1" or 1.5". Not a clue.
4 - Front suspension, will the shocks from the red kid's bike be enough?
5 - Rear suspension, would the single coil/piston thing from the red kid's bike be enough (I'll be moving it somewhere)?

And also, any other "better watch out for this" or "make sure when you do this, you do it like this" tips that might not be obvious to a first time builder? Keep in mind, I don't even know the names for most of the bike parts and have never designed a bike before, so I'm perhaps shockingly ignorant/innocent.

Thanks

 

[TopCat]

I think one thing you'll have to consider before going into this big build is the amount of peddling you plan on doing.

I bought a Schwinn Spoiler chopper a couple years ago as I thought it looked cool. Little did I know at the time that it would be a pain in the arse to peddle. I can do about maybe 200/300 yards and my ankles and butt are sore, cant wait to get my motor up and running.

One thing to note with recumbent style bikes is the riding position. With a normal style bike, when you hit a hill and drop down all the gears for easy peddling. Whats the next thing you do?

Stand up.......and put your weight on the peddles to help you up that big hill.

You DONT have that option with a recumbent style bike.

With a motor onboard those hills will be easier, but what if your battery runs out and your far from home?
You'll have to peddle it home, with all the added weight of motor and batts....puff pant puff pant.

Regards
Tom

 

[amberwolf]

1 - What the wheel-wheel (on ground contact) distance should be? ("wheelbase?") Is 47" good/bad/long/average/short?

Seems kinda short, about like an average bike. Typically this is called an SWB (Short Wheel Base), and my guess is you'll end up with a HighRacer setup with that short a wheel base, with the seat up fairly high, nearly at that of the regular bike. But it depends on your preferences.

CrazyBike2 is nearly twice that length between contact patches, and would be considered a LWB (Long Wheel Base).

2 - What a good ride height for the seat would be, assuming a natural posture?

As noted above, that depends on your preferences for visibility and ease of seeing around you. Personally I don't really like being up at pickup-truck seat height, which is where most regular bikes put me. I prefer being at normal car-seat height, and that's about where CrazyBike2 is setup to put me.

The old unfinished ReCycle on my Electricle blog would've been a LWB Lowracer, putting me down where F1 car seat height would be. Aero efficient, but pretty hard to see and be seen.

3 - How thick my frame should be, if I'm using any of that square/box tubing I showed from the exercise machines. It's not fancy chromoly or anything, just plain mild steel. I have no idea whether a 0.75" square pipe at 1/16" thick would be enough, or whether it should be 1" or 1.5". Not a clue.

Mostly, look at what existing frame designs that are similar to yours can use. If you see big single tubes, there's probably a reason for it. If you see smaller parallel ones with triangulation between them, that will probably work for you. If you leave out the triangulation in one that had it, then it probably won't work as well as it should, and may fail catastrophically. I recommend using triangulation in any frame as much as possible for strength and reducing flex, but sometimes you can't do it or it weighs to much, etc.

I also highly recommend using old classic 10-speed bikes for frame material, because many of them have long straight tubes of good cromoly that you can easily re-use, and it is very light and strong. Depending on the design you may well be able to reuse whole sections of a bike as they are, maybe bending tubing to match angles if they're close enough already. this site:
http://recycledrecumbent.com
has some handy info on that kind of thing, including splicing tubing from short sections. But this kind of tubing is very superior to the steel you've got on those ex-exercise machines, which is heavy and thick and often soft steel. I've used it and many other kinds of scrap steel to build things with, and given the choice I'd rather recycle known-good bike frames to do it with, even if I have to splice sections together.

4 - Front suspension, will the shocks from the red kid's bike be enough?
5 - Rear suspension, would the single coil/piston thing from the red kid's bike be enough (I'll be moving it somewhere)?

Probably not, but it depends on your road conditions. If you have roads smooth enough to ride without suspension at all, normally, then yeah, they'll probably be fine. But if you have rough roads, you'll want "real" suspension, which you can either build (a little difficult and rather time consuming if you deviate from established designs) or find used (depends on thrift stores and other used sources in your area) or buy new (expensive).

If you re-use the rear shock, try to keep all the angles and lengths of levers the same, or the shock will not experience the same loading and won't give you the same travel/etc. as designed, and may not do anything at all. As it is it may be such a light spring that just the one would be totally ineffective, compressing fully as soon as you put your weight on the bike.

I've tried designing my own rear suspension for CB2 a few times, and not come up with something that actually works or that I like yet. Still designing my own for the rear of the new bike, too, but it is totally untested. Using an old dirtbike motorcycle-class shock on it this time, which shoudl easily handle the weight loads I will have, but it's big and heavy. Front suspension there are a number of ways to make your own, and lots of sources of springs and whatnot, but when you re-use a spring from something else, you must consider the original usage and loading on it to know if it might work on your own design.

And also, any other "better watch out for this" or "make sure when you do this, you do it like this" tips that might not be obvious to a first time builder?

Mostly that you read up on existing 'bents to find the things you *don't* want to do. Either becuase they turned out to be problematic or because they go in a direction you're not wanting.

And just a general warning that you will probably build at least two frames. The first one will probably not work the way you want it to for many unforeseen reasons, and modifying it is often more work than starting over. :lol:

Keep in mind, I don't even know the names for most of the bike parts and have never designed a bike before, so I'm perhaps shockingly ignorant/innocent.

I would highly recommend reading thru Sheldon Brown's bicycle maintenance website
http://www.sheldonbrown.com
before sitting down to design it. You will learn things from all the extra information there that will influence your design in ways you haven't even thought of yet. That's what happened to me, and I have learned dozens of times what I knew before I went there from that site.

If nothing else, you'll become familiar with the names for common bike parts, and even brand names, which will in turn make it much easier for you to quickly grasp articles and posts describing ideas, functions, problems, and solutions to stuff you want to do on your bike. Without knowing the terminology, much of the information out there takes a lot more time to grasp (or at least, it did for me).

There is also a good recumbent site to skim thru, at least:
http://www.bentrideronline.com
where you will find more information about existing bikes than you'll ever find time to comprehend :lol: and links to even more. This info is useful for seeing what is already popular and *why*, and what people *don't* like and why, which in turn will help you make certain decisions about where you want to start at. It also has a forum with many existing discussions (and of course you can ask your own questions, too), that might help you make certain decisions.

Both of these sites heavily influenced both my original abandoned ReCycle and my later CrazyBike2 designs, and my experimentation from there has guided me toward the newer bike's design, which is still in-progress.

 

[MattsAwesomeStuff]

I can do about maybe 200/300 yards and my ankles and butt are sore, cant wait to get my motor up and running.

Odd, perhaps you are uniquely disabled in this manner? Oddball bone/muscle lengths/sizes? I've not heard of anyone becoming sore at such short distances. I do know that after riding about 1200km on a mountain bike last year (probably more than the rest of my life combined), my ass still got sore after about 45 minutes every day, and almost unrideably sore after 3 hours, even when taking breaks. I didn't mention above, but it's a huge reason I want to go recumbent, because my ass is the limiting factor on my rides moreso than my legs or cardio.

One thing to note with recumbent style bikes is the riding position. With a normal style bike, when you hit a hill and drop down all the gears for easy peddling. Whats the next thing you do? Stand up.......and put your weight on the peddles to help you up that big hill.

I hear this often. 2 solutions/explanations for why it may not be as important as claimed:

1 - Recumbents use different muscles, or, rather the same muscles in different magnitudes. This is often noticed only by highly trained athletes who've optimized their bodies for uprights.
2 - Standing up doesn't help improve your *average* power output. Obviously there is no free lunch. What it does is allow you to "bank" energy somewhat slowly standing up, and then release it all at once as you shove down on a pedal, lurching you up a hill in discrete amounts. Your momentary power output being much higher than you could achieve continuously. This same effect can be accomplished by lowering gearing for equivalent continuous effort.

Obviously I have no experience to claim either way, and will have to figure this out and how much it matters to me. And, either way it's irrelevant, there are no design choices to make that affect this. Only to abandon it entirely and not build a recumbent, something I am settled on doing.

Typically this is called an SWB (Short Wheel Base), and my guess is you'll end up with a HighRacer setup with that short a wheel base, with the seat up fairly high, nearly at that of the regular bike. But it depends on your preferences.

Well, as I stated, I am set on building an SWB. HighRacer/Midracer... not sure. The 20" front tire and possibly S-frame should help get me tucked down. I've never seen a recumbent with a 30" seat height, I certainly hope I'm nowhere near that high. Within that SWB/high/mid context, is 47" appropriate (I'm 6' tall)?

If you see big single tubes, there's probably a reason for it. If you see smaller parallel ones with triangulation between them, that will probably work for you.

I thought big singles vs. triangles was an arbitrary choice. That a larger pipe is stronger for the weight (thinner material, up until the "beer can effect" [real engineering term] occurs around 60-70+ diameter : wall thickness ratio). Or, triangles are stronger for weight when covering large areas. One is not superior to the other in terms of strength, each has to be engineered to the situation.

I see almost equal designs with both methods.

I also highly recommend using old classic 10-speed bikes for frame material, because many of them have long straight tubes of good cromoly that you can easily re-use, and it is very light and strong.

Interesting. I didn't know chromoly was that old of a common material. I presumed anything but high-end frames were plain mild carbon steel. That's encouraging.

However, it would force me to go with a triangular frame, something I think is more complicated and uglier. There's no way I'm using a 1" tube as a single straight pipe and not snapping it. I'll definitely keep that in mind though, especially for everything rear of the start of the seat.

If you re-use the rear shock, try to keep all the angles and lengths of levers the same, or the shock will not experience the same loading and won't give you the same travel/etc. as designed, and may not do anything at all. As it is it may be such a light spring that just the one would be totally ineffective, compressing fully as soon as you put your weight on the bike.

Well, I'm 200lbs and when I rode that little 20" red bike I had to jump and shove to get the shocks to compress even an inch, and the back never bottomed out if I tried. So, that's encouraging.

As to angles, far as I can figure, the midpoint on the shock needs to be kept perpendicular to the pivot. And for leverage, I think it's linearly proportional to the distance of that line. Meaning, if I move it 2x as far away from the pivot, it will need to be 2x as soft for equivalent travel. I think it's a bit hard right now, so maybe that's good. I'll look at getting a pair of these. I may try your idea of using front shocks in the rear too.

...

Thanks for the tips and the links, I'll continue doing more research.

 

[recumpence]

other Matt,

Oh no! I forgot. You are one of the mid-western low racer crowd.

I spent years discussing this issue with you guys, on the old hpv list. I was "big wheels are better" Berger. Since those days, sales of high racers have out-numbered sales of low racers many times over. RAAM, crits, etc. have been won by high racers. High racers have gone from 559, and 571 wheels to mostly 622 wheels. Last time I will mention it.

Warren

You may be mixing me up with someone else. I am in the midwest, but I only own two recumbents at the moment.

I agree big wheels are faster (we are not including the No-Com in this discussion are we? :wink: ).

I am addressing the ease of use aspect. I totally agree that big wheels tend to be faster. No disagreement there.

Matt

 

[amberwolf]

I'd say you are correct about the riding strength of muscles and whatnot, because I had to almost relearn riding when I changed to the 'bent, and all my muscles leg, back, and arms had be retrained, which took months. But I was able before motorizing the bike to climb part of North Mountain on 7th Street, and that's a heck of a hill. I had to walk it the rest of the way up, though, partly because my knees are worn out and I really can't take the pain for very long. If it werent' for that, though, I think I might've been able to eventually make it all the way up.

I've never seen a recumbent with a 30" seat height, I certainly hope I'm nowhere near that high. Within that SWB/high/mid context, is 47" appropriate (I'm 6' tall)?

That I don't know. I arrived at my own setup by experimentation more than anything else. About the only specific choices I made were:
--to try to get the seat at about car-driver height, and setup so that I could easily put my feet on the ground just by sitting up, for stops.
--To keep the front wheel out beyond my feet, so I didn't have to have my feet up high, as my body mass was already mostly going to be pretty high up.
These two things basically forced me into the semi-recumbent LWB setup I have now, which I find I like quite a lot. But not everyone likes that riding position, or having such a long bike (almost 9 feet long!).

If you have the opportunity to do so, you could try riding other people's recumbents to see which ones suit you better.

I thought big singles vs. triangles was an arbitrary choice. That a larger pipe is stronger for the weight (thinner material, up until the "beer can effect" [real engineering term] occurs around 60-70+ diameter : wall thickness ratio). Or, triangles are stronger for weight when covering large areas. One is not superior to the other in terms of strength, each has to be engineered to the situation.

I don't really knwo for sure. It's just been my experience so far that in what I've built, triangulated stuff works better. The only thing I've used a single-beam for so far that has ever had to carry much weight is my cargo pod rails on CrazyBike2, but even that wiggles and sways under loads.

Interesting. I didn't know chromoly was that old of a common material. I presumed anything but high-end frames were plain mild carbon steel. That's encouraging.

Many of the old ten speed (OTS) bikes I have run across are either obviously cromoly from the light weight and thin wall thickness vs strength, or are actually marked as such, either by name or with a cromoly type number. Typically the ones I have found are brazed together, and are of pretty good quality (frame-wise) despite the horrible condition of components on them, such as rusted chains, freewheel/cassette/etc., chainrings, brakes, rotted tires, cables, and so on. The frames are usually not rusty even inside the tubing, which plain steel frames almost certainly would be. Sometimes they are rusted at some points, but nothing like plain steel ones in the same condition usually are.

THe ones that are welded together instead of brazed are more commonly plain steel, and much heavier and thicker-walled.

However, it would force me to go with a triangular frame, something I think is more complicated and uglier. There's no way I'm using a 1" tube as a single straight pipe and not snapping it. I'll definitely keep that in mind though, especially for everything rear of the start of the seat.

Yeah, no way to use a single 1" tube as an unsupported crossbeam. :lol: I mostly suggested the triangulated frame as it is less susceptible to twisting and can be a lot stronger for holding more weight, depending on exactly what you want to carry (especially since you're 200lbs yourself). If using lightweight steel like cromoly, the triangulated frame may even weigh less than a single-beam frame made of the exercise machine steel (which tends to be really thick/heavy stuff cuz weight doesn't matter in that application, and in fact can be a bonus to stabilize it).

Well, I'm 200lbs and when I rode that little 20" red bike I had to jump and shove to get the shocks to compress even an inch, and the back never bottomed out if I tried. So, that's encouraging.

yes, it is, though I guess that means it's totally for show as a kid's bike. :lol:

One thing to remember when you hit a pothole or a bump, suspension reacts differently than when you just statically compress or release it, because as I understand it, the effective weight can be more than doubled at the impact depending on how far the drop is.

As to angles, far as I can figure, the midpoint on the shock needs to be kept perpendicular to the pivot. And for leverage, I think it's linearly proportional to the distance of that line. Meaning, if I move it 2x as far away from the pivot, it will need to be 2x as soft for equivalent travel. I think it's a bit hard right now, so maybe that's good.

I have forgotten the name of the file, but there is a PDF out there for figuring out suspension stuff. IIRC it was linked to me in one of my threads asking about suspension, but I can't recall which one.

I'll look at getting a pair of these. I may try your idea of using front shocks in the rear too.

I still don't know if that will work or not, but if they're adjustable types like the Manitou Skareb I intended to try on that, it should.

 

[MattsAwesomeStuff]

It's just been my experience so far that in what I've built, triangulated stuff works better. The only thing I've used a single-beam for so far that has ever had to carry much weight is my cargo pod rails on CrazyBike2, but even that wiggles and sways under loads.

Well, the problem is that I probably cannot find thick enough steel from existing bike frames, unless I salvage a recumbent. There will be no such thing as a straight pipe that is large and strong enough out of a diamond frame to be a single beam. So, my choices are: Recycled Triangular or New Single, but not Recycled Single.

The deal with triangles is that they have to be rather large to get the strength benefits out of them. Obviously a very narrow/pointy triangle will be no better than a solid single, perhaps worse for weight. And, because it's a recumbent, there's simply not much room for a triangle, which is why I presume most recumbents use a single.

I guess I'm going single until the seat using the crap boxframe, and then triangle-up everything rear of there.

 

[MattsAwesomeStuff]

Read a few hundred more articles. Some of which I even understood and could make use of. Lacking motivation, feeling swamped, grindstone time.

Part of the difficulty of this whole process is separating wheat from the chaff. Bicyclers are optimization nazis and it's never really obvious whether they're arguing and insisting on variable ranges that have minutia hairsplitting improvements that are clouding my brain, or whether it's something big like "Put the seat far enough forward or your knees will clip the handlebars", another should've-been-obvious thing I just came across.

Insisting on decisions and progress for tonight has yielded:

1 - 47" wheelbase unless I decide otherwise. Too many opinions. Don't care.

2 - On an upright my seat height was 39" and my head height was 68". My new seat height will be 20-23", and ride height 46-49". 19" lower than before. Great. It might be easier to pedal.

3 - My ass-to-heels measurement is 45". This helps decide crank-seat distance.

4 - Crank radius is 8". Worst heel radius on crank is 13". So, wherever I mount the crank has to be 13" away from the front tire/fender. This helps figure out the lowest front frame angle or length forward of the handlebars.

5 - I'm not screwing with a chainline that could strike the wheel. I'll raise the seat up a foot if I have to, which I won't.

6 - Seat angle no less than 34' (view/chin-chest annoyance) and no more than 52' (is apparently uncomfortably upright to pedal with feet forward). 40-ish sounds fine. Whatever. It'll be slightly adjustable without screwing up the ass-heel distance.

7 - I might be able to arrange for the rear suspension to pivot *at* the motor drive output using my own bearings. If so, no chain stretch issues when the suspension compresses on a bump. If not, maybe screw with chain stretch idlers on the upper chain on the front (human-powered side). If not, oh well, no rear suspension, hope the batteries and motor don't snap if I hit a bump.

8 - If I end up just using the drill gearbox as is.. I'm leaving the chuck. I'll carry a damned chuck key and this will be my clutch if I can't find/build this double-opposing freewheeling system that no one's got the hang of yet. If the batteries die and I don't want to crank over the motor while pedaling, I'll just loosen the chuck a bunch so I'm only spinning the 90' outboard gearbox prop and not the geardown/motor. Shouldn't be too often an occurrence anyway. One extra freewheel only to coast pedals under motor power simplifies a lot.

9 - No such thing as low-ish upright seat and low crank. Puts your crotch up near the steering pivot. Can't slide it all back, because then crank then runs too close to the tire and there's heel strike. If you want to move back, the crank has to move upward arcwise around the 13" clearance to the front wheel. Will settle for higher crank rather than lower seat angle or larger seat height.

All together... torso is scaled small, but otherwise measurements check out for something like this:

Purple is cargo rack/paniers and batteries. Green is motor. Dark green is reduction gearbox. Bluegreen is 90' gearbox. Handlebars are screwy 'cause I only had distances not angles and chose for distances to be exact while I eyeballed, and handlebars were drawn last.

Rear wheel isn't perfectly rotated, things will shuffle, didn't draw chainlines, but.. good enough for me to see that everything will work out.

Perfect and Never has yielded to Shitty and Sooner. Including my artistic abilities.

 

[CrazyJerry]

You may not be into lwb but your earlier draft shows a position very comparable to my modified Rans Tailwind. With dual 26" height is right up there so you would not have to worry about visibility, and the ride is like butter.
~CrazyJerry

 

[MattsAwesomeStuff]

You may not be into lwb but your earlier draft shows a position very comparable to my modified Rans Tailwind. With dual 26" height is right up there so you would not have to worry about visibility, and the ride is like butter.

I don't understand. That's somewhat of a random post/comment to make. It's similar in that it's.. a recumbent? And the angle is not as aggressively inclined? I don't really see the similarity. I'd actually say your example is almost as dissimilar as could be. Almost completely upright and bottom bracket well below the seat. A random picture of any recumbent, such as those I posted at the start of the thread has as much or more similarity.

And yes, not into LWB, nor excessive ride height, nor dual 26", it's not what I've chosen to build since the start. I want short, car-transportable recumbent that's at a middle ground balance between the grampa-bike lawn-chair-on-a-rick-shaw and the speed-demon-road-hugger extremes. Low enough to make aerodynamic gains, high enough to avoid turning, visibility, or posture problems.

 

[Warren]

Crazy Jerry,

Save your breathe. Matt is intent on reliving the 1980's. Those old short wheelbase bikes with the tiny front wheels, hamster steering, and your feet way ahead of the front wheel.

Warren

 

[CrazyJerry]

:lol:
I needed that!
Have a good day!
~CrazyJerry

 

[recumpence]

Crazy Jerry,

Save your breathe. Matt is intent on reliving the 1980's. Those old short wheelbase bikes with the tiny front wheels, hamster steering, and your feet way ahead of the front wheel.

Warren

So, are you kidding around, or is this truly a comment meant to be as rude as you are coming across?

What is up with you?

 

[REdiculous]

I'm sure I could ride that Rans and not look too goofy. That other design looks like it could be a little more difficult to operate, and I think it looks old-school the way wearing hammer pants would make you look old-school.

Anyway!...
I gotta question the proposed drivetrain. Even though you might gain some efficiency by being able to change gears, you're having to drop motor rpm to crank rpm just to raise it again - if you can take the crank out of it I think you'd be better off. Also I gotta wonder what you're using for a right-angle, because the torque will be quite mighty I imagine. I'm not trying to keep count, but that's probably 2¢ worth...take it easy.

 

[MattsAwesomeStuff]

I gotta question the proposed drivetrain. Even though you might gain some efficiency by being able to change gears, you're having to drop motor rpm to crank rpm just to raise it again - if you can take the crank out of it I think you'd be better off.

Not quite sure I follow. Maybe, you're saying that I'll be gearing the motor way down to turn the big crank slow enough, which then turns the back wheel at a higher rpm than the crank?

Let me correct things. I will be moving the Blue Bike's crank up to where the pedals are (note my fabulous MSpainting skills). Under/behind the seat won't have a full size crank, no need for one. I'll probably have a pair of 3" sprockets on counter-rotating freewheels (I could go smaller but I want more teeth on a chain? Someone correct me if my logic is bad). Motor drives the axle to the rear wheel, the actual crank where my feet are sometimes helps the motor on the 2nd sprocket. The reason I left the whole big crank behind the seat is that I don't have a picture of a 3" sprocket to edit into place and... maybe that's not obvious because of my artistic skills but it was just a crude sketch and I was lazy

Was that your concern or did I misinterpret you?

Also I gotta wonder what you're using for a right-angle, because the torque will be quite mighty I imagine.

I've probably overwhelmed you with details. Back in the first post, I covered this.

Silly plan: A hand-drill, since it has bevel gears.
Shitty plan: A 90' drill adapter.
Actual plan: 90' gearbox from a tiny (1.5hp) outboard motor. Here's a pic of the one (I think) my friend is sending me:

If you can't picture what it is... you know the motor at the back of a boat. The shaft goes vertically down into the water, but then has to bend 90' to turn the propeller on a horizontal shaft. So they have bevel gears (maybe worm gears, but I'm pretty sure bevel) in a little waterproof aluminum gearbox.

Normal outboard motors, even for the smallest fishing boats are big, 10-15 horsepower. But this one's from some tiny trolling motor, like you'd mount to a canoe or some other tiny 1-man boat. It's mated to a 1.5hp engine, which is about what my motor is, so it's about appropriately sized power-wise. Torque-wise it might be a tad light since a propeller spins fairly fast, but then, it's way overbuilt too and the shaft sizes seem about right.

My only concern is cooling since the gearbox was originally designed to be, obviously, immersed in water. I'll just have to make sure it has thick enough oil and such. Again, it's overbuilt so I'm not worried.

It might have internal geardown too, I don't know yet. Looking at the math briefly, before the 90' adapter:

Motor top continuous speed: 3200 RPM (battery voltage is high enough to overdrive it to around 5000).
Drill gearbox: 38:1 dual-stage.

That gives me 84 RPM. A good cadence for a full size crank on the big chainring down to the tiny cassette sprocket at 30km/hour (or whatever the math works out to). But, not for 50km/h (30mph) top speed on a 3" drive sprocket rather than 8" or whatever a normal chainring was. I'm looking at double the speed and 3:8 the sprocket size. So, I'm 5.3 times too slow. I can't make the small rear sprocket any smaller, and I don't want to make the chainring any bigger, so I have to make the motor speed faster I guess. To undo 5.3x of geardown, what I will probably end up doing is removing one of the stages of the drill's gearbox (probably split evenly around 1:6 each, so, that'll give me 6x RPM back).

That, of course, unless the propeller gearbox isn't 1:1.

What would be perfect is if the prop gearbox was internally around a 6:1, then I could scrap the drill gearbox entirely.

I don't know anything about boats or engines so, I'll figure it out when I see it.

 

[Warren]

other Matt,

"So, are you kidding around, or is this truly a comment meant to be as rude as you are coming across?"

Needed a smiley face I guess.

Warren