Framebuilder with interest in e-bikes and questions

[Belltownbikes]

Hello All - first post here, though I have spent some time looking through many of the threads on this site. There is a *lot* of information here.

Anyway, I am a custom framebuilder - low volume - hobby gone crazy in the basement. I've only been building for 6 years, and only have 65 frames to my name. I fillet braze steel, and have built mtbs, commuter 650Bs, Monster cross and normal-ish road bikes. I've been wanting to tackle an electric bike for some time now.

I'm thinking a long-bike, like a big dummy. I want this bike to commute to my paying gig, run errands in town and use a a fetch-vehicle when we're camping and don't want to move the bus.

I would like some input: what would you folks design into this sort of frame?

I want to keep things looking more pedal bike like than motor bike like. I'd like to be able to hit 30mph, but cruise at 25 or so. I still want to pedal this thing, so rider position will be like a normal road bike.

I'm thinking hardtail with a front fork. 26" downhill wheels with fat slicks. I'd like to go with a drop bar, but that might be out due to the throttle...is a drop bar doable?

I'm thinking a mid-motor (that lightning rod setup is cool). Should it go down low under the DT, or behind the ST? Or is a hub motor better? My commute is hilly.

Battery mounting could be rearward, outboard of the rear wheel. Or it could be in the front triangle. Would double DTs be worth the fabrication hassle? Seems like a platform could be made for batteries there, and also act as kind of a fender. How about wiring - any special considerations there? Waterproofness? This thing would be carried outside the bus when we're roadtripping.

I have a blank page here, and can put just about anything I want together - I would really appreciate your input. The frame for me will be the easy part, I'll have many more questions about the batteries and controllers and such...the only LIPO experience I have is with my boy's RC cars and such.

If you have any interest at all, this is where I hang some pics of my stuff:

https://www.flickr.com/photos/belltownbikes/

Thanks, Good day - Bob

 

[Drunkskunk]

Welcome to the forum.

From what you described, a mid drive sounds like your best choice. They are the most complicated to setup and maintain, but also have the widest range of functionality.

You may also want to look into full suspension. if you plan to cruise above 30mph, you will do much better with a rear suspension as well. A few inches travel with a real shock and dampener will greatly improve ride quality, handling, and braking.

Bafang 750w bb kit is one route, but a much better system is the Stokemonkey offered by Ebikes.ca



Before you invest the time and money into a dedicated frame, I'd strongly suggest slapping a basic kit on a conventional bike and giving it a few months of riding. You will change your mind at least twice about what features you want and need in the first 1000 miles of riding, and investing a bit now in a basic kit will save you thousands later when you've committed to a system that experience says is what you need.

 

[dogman dan]

I sketched out my rough idea of a perfect commuters frame, and would love to see somebody smart refine it and build it.

Not a true longtail, but longer. Long enough to make it quite comfy at 30mph. Not twitchy like an overloaded MTB gets from the short wheelbase.

The basic features are 4 bar rear suspension linkage. The classic linkage can be bought off the shelf now on fairly cheap bikes, such as the Genesis. But the difference here, is lengthening the frame so the linkage fits behind the seat tube rather than in front. This leaves the space up front uncluttered for a large battery. Could be a bag from EM3ev, or a custom box.

Then, no shaky jake bolt on rack, but rather a solidly built pannier rack that is solidly welded or in your case brazed to the frame. Frame tubes thick and very stiff, so you don't get the tail wagging the dog when packing a big load.

Rear dropouts would include built in torque plates if a hubmotor is used.

Here is the sketch, go for it and use any of my ideas if you like.

But if you want a full longtail, you might check out my frankenbike build, and steal some ideas from there. Others may scoff full suspension, but I sure love having it when I am loaded to the max, and some A hole sends me off the shoulder into the gravel. Or, I fear no dirt roads. I can fly over washboards at 30 mph with ease.

http://endless-sphere.com/forums/viewtopic.php?f=6&t=28389&hilit=bouncing+betty

The only thing that could improve bouncing betty much, would be a mid drive. I'm contemplating building another, and putting the bafang 750w mid drive on it.

 

[dogman dan]

Your kids sure have a dang cool dad. That's beyond craft, and well into art.

Nice double dutch frame, but I think they carry better if the rack is attached to the head tube so it never swings.

That's one mod for betty I'm considering, a larger front basket. She can get pretty tail heavy when I load all the camping gear, two days of water, and 80 miles worth of batteries.

 

[Ykick]

Drunkskunk makes a great point - slap something together and use it before diving into the pool.

You’ll realize stuff you never expected and with your skills it wouldn’t be long before very “wise” adaptations come to fruition.

But for starters - IMO main points to consider in no particular order - battery & motor mounting, braking, comfort, load capacity, tires, handling, etc.

 

[Bikengineer]

If starting from scratch I'd mount 2 bottle batteries vertically behind seat tube. This will naturally lengthen wheelbase and centre the mass. If you want it for errands and to carry cargo use small diameter wheels and incorporate low racks/baskets over front and back. Think a cross between truckbike and longtail. By all means incorporate suspension but from a simplicity viewpoint fat low pressure pneumatic tyres are well proven.

At least that's what I'm building this weekend with 250w powered upfront.

 

[spinningmagnets]

What city/state are you in? I used to have a full suspension longtail, vaguely similar to dogmans...it was a wonderful bike, and I may make another one someday. I would still have it if I had more room. My ultimate commuter would be an edgerunner, 20-inch rear wheel longtail cargobike, fat 26-inch front tire...

 

[sculptingman]

This is not a long tail... But I built it on a Spot Ajax to run like a regular bike, cruise pretty easy at 25, and carry panniers full of groceries.

I would avoid drop bars... It doesn't buy you anything in speed... And you're more alert in traffic at higher speed with your head high.
This one is aluminum... With a fairly short wheelbase... But I very nearly bought a used Fisher Sawyer 29er to convert for its cro-moly frame and longer wheelbase.

The mid-drive motor with downtube rigid mounted battery gives the bike a real fine C of G...and the downtube battery being a little forward really makes panniers full of groceries feel less ass heavy.

If building a custom frame for the Bafang 750... Be aware that the bafang's pedals are a trifle askew to the right side...and its chainline is way off at 50mm or more. I have been looking for a custom frame builder for a while...but had a hard time finding anyone to take on this job.... Part of what I wanted was to build a custom frame with the 68mm BB offset to the left such that I could achieve the precise chainline alignment I needed for a gates belt drive.

PM me if you want to discuss this in detail... I have done a Lot of prep work to designing a custom electric frame around the Bafang motor... Including digital modeling.

 

[dogman dan]

Hard to beat that for basic commuting. Mid drive and mid mount battery. Allows a good load in back with no rear overloading. It's near perfect for good roads. We have none here, summer heat ruins them in 3 years. My most common route is now 10 years old, and getting worse fast.

Much depends on the speed you intend to ride, My sketch was aimed at those with a desire to ride potholed roads and dirt shortcuts at 30 mph. Or more.

I'd prefer to carry use the longer frame to fit suspension for those speeds on shit roads. But for real cargo carry, you want the funny bike with the huge bathtub cargo space in front of the rider. The Dutch have made some amazing cargo bikes.

 

[Belltownbikes]

Thanks for the pointers all. Like I said, my e-bike studying has just started.

I appreciate the advice to put the propulsion on something and start learning from there. I am pretty set on the form of the frame at this point though. I basically want to electrify a long tail I've had in my head for a while - they can carry what I need to, they are comfortable and steady at speed, and the long wheelbase makes the frame forgiving on rough roads. I do not think that I'd be into rear suspension - hell, I don't even ride a FS mtb - half of my mtbs are no suspension. I will put a front susupension fork on, and run the biggest non-fatbike rubber I can. I realize that I'll come up with a number of changes in the first 1000 miles - but this wouldn't be the first (or fifth) frame that I've built, ridden and then sawed up and modified or turned into wind chimes. Part of the mania I guess. They're all prototypes.

While early, I my eyes like the Schmaker RC drive or the lightning rod or the stokemonkey. I realilze the is all over the place for mid drives - I would welcome any thoughts on these propulsion systems. I like the Schumaker stuff for it's light weight and neat design, and also for the very low drag of the e-drive system when pedaling. The stoke monkey is cool too - no geared drives, but may be more drag when pedaling no boost - or perhaps I'm not thinking right. The lightening rod is cool, but the true best use of that drive might be for a not purpose-built frame. I just looked at the bafang - and that is neat too - not so keen on the proprietary crank though.

Anyway, I figure a few months to zero in on the propulsion. Tehn I'll have to purchase it. Then design. The fabrication will be the easy part by this point. Given my backlog of projects, this will probably be a next winter deal for me.

Again, thanks for the thoughts so far, and I truly welcome any input.

Cheers - Bob

 

[dogman dan]

Heat cracked roads similar to riding over spilled 2x4's on the road, and a construction work ruined lower back is why I fell in love with FS. Being able to ride through the ditch at 30 mph when a pickup truck runs me off the pavement is a bonus. I simply could not stand a 40-80 mile ride without suspension. Pedal forward hammers me even worse, 5 miles my max with a pedal forward bike. I gotta stand the pedals, and have suspension when sitting the saddle.

Younger guys with less destroyed bodies nearly always feel no need for suspension on pavement.

Anyway, don't wait to build a bike to play with electric motors. A YES.com kit from ebay is cheap. But get a good battery, one that can handle anything you do later with a mid drive. It will last 2-4 years. Hauling ass around all summer at 30 mph might change your frame design some. Even if you do go hardtail on your cargo bike, I highly recommend an expensive front fork. It will really improve the handling if you ride dirt roads. Can't steer unless the front tire is touching the ground.

Bear in mind, I'm a kook, nearly the only one here with a FS longtail. Plot a bell curve of anything, and I'm always out there off the curve.

 

[tomjasz]

Part of what I wanted was to build a custom frame with the 68mm BB offset to the left such that I could achieve the precise chainline alignment I needed for a gates belt drive.

PM me if you want to discuss this in detail... I have done a Lot of prep work to designing a custom electric frame around the Bafang motor... Including digital modeling.

THAT would be an amazing build! Your current is really a good looking bike. I'd be thrilled if I could ride in that position! Nice saddle too. I've got one in my sights too.

Tom

 

[2007blueprius]

I love this thread and I have more questions than I have answears.

for starters I agree that coosing a ready made kit and slaping it on a frame you have allready is the place to start, than see what works and doesnt and go from there,

I contemplated for years what to do about an ebike, eventually I bought a ready made kit, slapped it on a 26 frame and done a test ride, shortly after I got some great ideas to put it on a frame I shouldnt have and long storry short I ended up buying another hub whhel, had that on a FS frame, not the best, while lots of fun very unstable, I do a fair bit of tinkering so a custom build is not out of the question, but I am not verry familiar with bike parts and for the most part I have been limited so far buying frames that had one thing or another that I could cut up and make a frankenbike.

I would love to see some speciffic details and recources on this thread, for example, what a proper headset angle is considered to be?

the one I had put together felt like I was about to fall over the handlebars even at full throttle, and riding with one hand was out of the question, the head tube is narower than anything else I have so I can't just bolt up a better fork, I could take some measurements off the fork, but where would one source a tube that is just the right inner diameter? short of cutting it off another bike, where do you get your parts for your custom frames?

Again each has their own confortable possition, I have 1 bike that fits me verry well so for the most part I will probably coppy that, but some speciffics as say the seat post angle? discussion would be interesting to read, what I mean on the prototipe I out together, I could barely hang on for dear life, very unconfortable to pedal for me, standing up, no way, granted some of that depends on eachs stature, but I would love to hear some input from an experienced frame builder. too laid back like a chopper with foreward controlls may be too much, mine felt like standing up while sitting down that is no good either, some of the licra setups, with the seat all the way up, A$$ in the air head down, not good either, some do it on MTBs, beats me, I am fixing to cut it up shortly but clueless as to which direction to head, I personally preffer heels touchng the ground while on the seat, handtle bars high, back almoast straight, more like a cruiser bike. Confortable

and also the swingarm.chainstay, how much is too much, or there isn't such a thing, I have no experience with long tails and cargo bikes, a few inches? maybe enough to mount the controller in on it in front of the wheel, for example say 26" wheel / 2 = 13, say controller lengh is about 8 inches, cople more inchese clearence between whhel and controler and BB, so say 2+8+2+13 = distance from BB to dropout, this is just a hypotetical example, or maybe one wants to get even more teknical and figure out the motors torque and tire to pavement break traction, total weight and leverage, oohhh this is not going well.

maybe just look to common practice, Cruiser frames are considered good confortable comuters, what do they have for common angles? like the steer tube etc

I am in unchartyed teritory here, beautifull work by the way where do you get your bits from most of the dropouts you use would do well for a hub motor/

George

 

[dogman dan]

Go buy a harbor freight angle finder and start looking at head angles of stuff in stores. That will tell you what's normal. I do recall threads someplace though, that talked head angles, and linked to some cool pages about frame geometry. Happy hunting.

When I built my frankenbike from two frames, I did this. Before I cut anything, I put wheels on the front frame and measured the height from the ground of the bottom bracket. Then when I assembled the longtail, I made sure when I was done the bb was still the same height.

This way, the head angle of the original frame was never changed. And then later, since it was a shock fork bike, I could change forks with not much change of angle.
As I understand it, more vertical is for quick steering. Low speed, stuff. For less wobble at high speed, less vertical. Sounds like you had you fork pretty vertical.

 

[Ykick]

...most of the dropouts you use would do well for a hub motor/

George

I thought the very same thing.

Love these frame builder threads....

 

[2007blueprius]

for example, this bike

http://s33.photobucket.com/user/DJP944/media/Mobile%20Uploads/D2096A0B-803B-4B8A-9EC4-BA2FEF92B9E0_zpseeg2mehs.jpg.html

I love just about everything about hou it is set up, except that its all rigid, and probably tiny, I am only 5'8" but even that would probably feel like a clownbike, if everything was to proportion, on 29"wheels and the head tube a little higher, FS, that would be about my cup of tea maybe a little longer tail

 

[2007blueprius]

Go buy a harbor freight angle finder and start looking at head angles of stuff in stores. That will tell you what's normal. I do recall threads someplace though, that talked head angles, and linked to some cool pages about frame geometry. Happy hunting.

When I built my frankenbike from two frames, I did this. Before I cut anything, I put wheels on the front frame and measured the height from the ground of the bottom bracket. Then when I assembled the longtail, I made sure when I was done the bb was still the same height.

This way, the head angle of the original frame was never changed. And then later, since it was a shock fork bike, I could change forks with not much change of angle.
As I understand it, more vertical is for quick steering. Low speed, stuff. For less wobble at high speed, less vertical. Sounds like you had you fork pretty vertical.

that was my backup plan, I have the one bike that I like a lot, I was just wondering how a custom builder goes about picking all those values when starting from scratch, is it just a wild guess? how long to cut the downtube/backbone, especially if building for a speciffic rider, as in yourself, do you measure your inseam, etc, wish some of those bikeshops did fitings, unfortunatelly most arround here are barely retail outlets, nothing to learn there, I was wondering if there is a certain desirabledistance the BB should be foreward of the seat,

I have seen the recumbents which go to the extreme forward BB, and one lay down bike that had the BB behind and above the rear wheel , both with supposed advantages I don't understand, but most bikes are a few inches forward, than again I tend to overthink things, maybe its just the looks

 

[sculptingman]

Framebuilding is a pretty complex subject.

The geometry of a bike frame and its fork determine everything about how the bike will handle, and how comfortable it will be to ride.

Fork offset and head tube angle determine 'trail' the difference between where the tire touches the ground and where the forks centerline of rotation hit the ground,,, and that affects steering. ( is the bike nimble? Or does it stay on track for no hands riding)

Generally, the faster the bike is intended to run, the longer the wheelbase you want, and the more laid back the head tube angle or wider fork offset to achieve longer trail.
Also... Whether the frame is suspended or not affects how the bike feels and how well it can take higher speed...as well as the efficiency with which the rider ( or motor) can Impart energy into a turning wheel.

For a higher powered Ebike, I would advise a longer wheelbase... Going uphill a high powered bike can pop wheelies when you don't want to to ( especially if the weight of motor and batteries is high and skewed toward the rear.)

I recommend looking Into what has been called G2 geometry- which was developed by Gary Fisher to improve downhill handling of mountain bikes... Which have a disadvantageous tendency to under or oversteer depending on who made them.

Because I was designing an optimal city commuter, rather than going for high speed..and part of this project was about achieving a certain visual look... I went with the Spot Ajax frame.
But when I was thinking about optimizing the bike for speed and comfort, I was hunting for a Fisher Sawyer 29er... A really great, classic looking cruiser style mountain bike with G2 geometry.

And these choices were forced by my inability to find a qualified frame builder willing to build the frame I wanted.

 

[Belltownbikes]

Hey guys, circling back. The geometry question is fun - and can be a never ending debate. Just the proper trail can be a long debate.

So, trail is the distance measured horizontally from where the steering axis would intersect the ground back to where the tire patch hits the ground. This distance (mostly) determines how the bike steers. The trail depends on head angle, for offset and wheel/tire size. See here to experiment: http://yojimg.net/bike/web_tools/trailcalc.php

Zero trail would be like a unicycle. The bike would not self center at all. A long trail - say 90mm or so would make the bike overly prone to "falling" into a turn - it would feel choppery and wobly at speed. And any load on the handlebar would make the bike wobbly.

There is a whole bunch of proponents (of which I am one) - led by the resurgence of French-style randonneur bicycles that feel a low trail bike (horizontal distance around 30-40 mm) is ideal for a front load You can load up a handlebar bag with snacks and clothes and beer and the bike handles fine. There is no floppy steering. You can ride no-hands with a decent load on the front. Most "normal" road bikes wouldn't let you do this. (google Peter Weigle - he is a buddy and to the extent that I have a mentor - he is it. He is the master of the new school old school).

So, anyway. What about head angle for an ebike? Road bikes "normal" is 72 - 73 degrees. MTB "normal" these days is 70 degrees. There are plenty of downhill/slack bikes with head angles down to 67 and even 66 degrees. These are for going downhill on rough terrain. Lets say the use of theis ebike is for road/dirt road/occasional smooth singletrack. Are you going to carry you batteries or a basket up front? If so, aim for a trail in the 55mm range. Perhaps 73 degree head angle using a standard suspension fork (offset about 45 mm).

But really, a suspension fork is ill-suited to carry a load. I'd go with a 72 degree HTA with the suspension fork, and 26" tires. A little more trail for stability. About 60mm.

Front center. The horitonal distance from the BB to the front hub (roughly). This is determined by the size of the rider to a great extent, but can be varied to suit a specific purpose. Those "G2" bikes used relatively long front centers and short stems. This works good for 26" wheel mtbs - and really helped getting ejected over the bars. However, when the 29" wheel took over the XC market, much of the poor handling accusations were caused by those same long front centers/short stems. The front wheel needs some weight on it to turn the bike. When it is too far away, it's not weighted enough. I like to use a 100 - 110 mm stem on the 29er mtbs. I feel this gives a reasonable amount of weight on the front wheel. The FC falls where it may to suit the size of the rider. I'd design around a 100mm stem if I were using a "normal" flat or riser bar. If the bike is designed with one of the "alt bars" in mind I would adjust to suit. The Groovy Luv Handles are the best of the alt bars. Or get one custom bent of Ti by Andy at Watson Cycles.

But the steering is not the only factor to the bike's handling. Wheelbase is the other variable. This one is easier: the shorter the twitchier. On a normal touring frame the chaistays would be on the order of 18" long. On mtbs we aim for 16 - 17 (you want them short to do wheelies and such and keep a bunch of weight on the rear wheel). On a ebike, I'd run them way out: long tail or not. Unless youj have some sort of space contraint stays on the oder of 24" would make that bike ride like a caddy and give plenty of room for the drive system. But, for me - longtail + drive seems perfect.

OK - enough for now. Got to get the kids to bed. Keep the comments coming!

Any thoughts on the various drives I listed up there?

Cheers - B

 

[2007blueprius]

Thanks for the write up, I hope I am not hijacking your thread, I don't have any experience with mid drives and from your earlier description it would make sense but just a thought, you may be overthinking it, the mid drives are overly complicated not an issue in your case but it may outweigh the benefit.

the only experience I have is with a cheap 1000w ebay kit, I weigh $1.60 I bad it on a steel full suspension steel mtb, fairly heavy, the hub wheel was pushing 20 lbs alone, battery 1kw lithium, I would say well over 200 lbs all together, pushing 250, that setup was not shy at all, I ran it on some back roads 35mph speed limit and kept up with traffic I don't have a spedo but likely traffic wasn't running 35 only, fairly flat no pedaling, that bike was too uncomfortable to pedal anyway, went over a couple bridges, but did not stutter at all, 1kw of direct drive its a lot of power, I have a 6 hp go kart I would be curious one day to race my boy, it will be a close call and I recon the extra weight of the cart would be offset by the lighter rider.

I haven't taken any measurements yet but here is the setup in question http://endless-sphere.com/forums/viewtopic.php?f=3&t=58336 the entire setup was about 800 everything you need ad a few extras, couple different throttles, pedelec sensor, an extra regen controller, I ended up fudging the original hub with my too many ideas, so I ordered a new one after a few rides I laced it into a MC wheel, here I go with the ideas again.

I went back to your first post, I was considering a U channel for a DT on mine, just the right with of a battery, I think mine are 18650m I have yet to open it up

that titan bike thou not on the cheap side very badly built, I got the frame on CL for $40 so I don't care to cut it up, but for starters, reading your input supposedly head angle is 70 degrees bad idea, handles fine till you take a hand off the bars, I wanted to check my pocket make sure I did not loose my wallet no way, have to slow down to slow pedaling speed to do that, so I recon a roadbike angle would be preferable, I like 29ers, and I have a hardtail to work with also, but I don't know about a hard tail at 35MPH honestly, this bikes suspension was messed up when I was testing might as well be a hard tail, I ran over a root, and despite the weight of the battery back there and the heavy hub boy did it buck like a rodeo bull, and that was about half throttle.

anyway I end up going about it, I will likely end up with a 29er up front and a 21 MC in the back, which outer diameter is about the same as a 26, if I can fit a 29er fork on that bike I think it will change the head angle just enough considering it will raise the front end considerably and the rear suspension is due for some tweaking also, my only issue at the moment all my 29er forks have a stem that is too wide so I have to figure out where to get the proper head tube from hence the questions since I have to weld it on might as well .

other than that that is about all the feedback I can give you at this time, a 26 MTB geometry, bad for an ebike, for my statue at least 5'8", the green one in my posts is my favorite 29er, I am very comfortable on it but likely I wont use it for a ebike, it is all aluminum and I can not weld that.

I really think that for your first bike a plain hub should do, you wont build the perfect ebike the first try, just slap something together and enjoy it for a while, another mid of the road setups I like are Keplers friction drives, I think they are awesome, one of those I'd like for my green bike, for this buil I am aiming for a commuter that can handle potholes without cracking a frame and the reason for the motorcycle wheel build is so the tire will wear better

 

[tomjasz]

Custom crank forward? Ready!

 

[gogo]

Nice double dutch frame, but I think they carry better if the rack is attached to the head tube so it never swings.

Batteries wrapped around the headset is something I'd like to experiment with.

This guy emulated Wavecrest's battery positioning:
Subject: Lowdown Front Power

Stuff about steering geometry:
Experiments with rake and trail variations.

Bicycle construction contrasted with motorcycle:
Non-suspension bicycles use the frame flex and wheel 'give' to absorb some of the road shock. Motorcycles have rigid frame/wheels and use suspension for the purpose. Suspended bicycles are a mixture.

By all means incorporate suspension but from a simplicity viewpoint fat low pressure pneumatic tyres are well proven.

Perhaps a cargo bike could benefit from somewhat stiff frame/wheels and the 'ride' altered by changing the air pressure according to load?