Safe's Electric Bike Project #002

[safe]

The Beginning

I'm at the beginning of what will be a long process to build a very unique electric bike. The frame is made of 1.5" (0.065" 16 guage) mild steel square tubes, two per leg, welded together and then ground down to smooth. I then drilled from the top down through those tubes with a 1/2" drill bit which saved about 2 lbs per leg. The current weight of the frame is roughly 17 lbs, but the seat (which will be suspended) has not been added yet. The forks shown are not the actual forks that will be used since I haven't built them yet. The "D" cell batteries will fit inside the frame. There is no head tube (the thing that the fork attaches to) since it doesn't exist in the middle of the frame and the plating around it is only 16 guage thick so the head area is both extremely strong and lightweight saving probably a pound over what a regular head tube might have weighed. (the head tube is actually two tubes that are less than an inch on each end... the 3 inches in the middle is empty)

So what you see is the COMPLETE battery pack and frame combined, since the batteries will be inside the frame. Amazing how much room there is to play with now. (and it will have 40% more battery capacity than my old SLA project) Each leg of the frame (two per side) will hold 20 "D" cell batteries which means each leg adds up to exactly 24 volts. The total battery count is 80 "D" cells and you can go either 24 volts, 48 volts, or 96 volts for your final voltage depending on how you wire them together. It will require four 24 volt chargers. (which are about $20 each)

With a 52" wheelbase... this thing is designed to go fast and never flex... 8)

It has begun...

 

[fechter]

Cool. That's a lot of holes!

Is it going to have suspension?
It looks like the rear axle is going straight to the frame in the pic, but you might consider making the seat attachment on a suspension.

You're going to need some kind of study insulation material to separate the batteries from the frame. Bouncing around will tend to wear through most materials over time. It looks like it will be challenging to de-burr the holes on the inside of the tubes.

Think about where all the wires are going to come out. Plan how the wires will run along the frame and where the 'hairball' will hide.

 

[safe]

You're going to need some kind of study insulation material to separate the batteries from the frame. Bouncing around will tend to wear through most materials over time. It looks like it will be challenging to de-burr the holes on the inside of the tubes.

I'm on that already. I've welded a round tube with a drill attachment that will fit inside the frames square tubes and first grind away the drill fragments and then later sand them smooth. That was going to be in a later installment in this series. Obviously you can't place batteries inside something that has rough edges.

The overall bike will be without suspension... but the seat will be suspended on it's own swingarm. The reason for this is that I want a frame that is absolutely positively flex free at 100 mph. I will never need to go 100 mph, but I want the bike to feel at 60 mph that 100 mph is not a bad idea. Most regular bike frames are built for speeds of about 30 mph and that's without batteries attached.

You enter a "different handling reality" when your frame is so flex free that you can feel confident that you can stay in a lean at 30 mph and above and that if the tires slide a little you can bring it back without fear of a "high side". Frame flex is where "high sides" come from. (it's the process of the frame getting wound up after catching from a slide and then releasing the energy afterwards that throws you off)

I know this sounds "crazy" but I already have gotten my existing bike to slide in turns (at about ~32 mph) and it feels like you were carving through a turn like you were skiing... once you've learned how to slide then you feel a heck of a lot more confident going through the turns because you aren't worried about what might happen. (you already know how to react to circumstances and it's no big deal) Road Racers do this all day long... that's what they do at the race tracks... they slide into the turns, they slide through them, they slide the rear as they exist them... it's all very subtle and barely visible to the naked eye, but if you look really closely you can see it, the pros anyway... the novice racers don't slide much... I'd like to think that I'm building a bike designed for a pro level road racer. (sort of like how the street bikes are modeled after the race bikes even though most street riders will never know what the bike is capable of)

Suspension introduces a lot of flex because it's hard to do well. In a future more advanced project where I had certainty that I could eliminate flex then I'd like to try it. For now that's beyond my technical interests to pursue. (there's still a lot of work to be done just with this simple version)

Note: There's a another cross member that needs to be welded to the frame right near where the rear wheel fits. So basically go to the back and count forward about 14" and that's where the rear cross member needs to go. I'll probably get to that today.

About those wires: I figured that the fixed end caps would be at the back. From the back you would string a single wire INSIDE the square tubes (since there is plenty of room on the edges) to the front. At the front you have the spring to keep the batteries loaded and out from that you have the two positive and negative wires that are soldered into a female Deans Connector. (which I've grown to really like on my old project) You then create a wiring harness that merges everything as desired. Recharging simply means unplugging four Deans Connectors and plugging them into your chargers that have their own male Deans Connectors. It doesn't get much easier than that. :wink:

 

[safe]

I started today thinking I was going to weld the cross member in the back, but then I starting thinking about alignment issues and the day sort of evaporated. (I also managed to get two rides in during the day) Anyway, after much pondering I think I've figured out a workable design for an engine mount. Tomorrow? Hopefully yes, but the heat is getting bad and it's getting harder to work when the garage gets up to 90 degrees or more...

 

[safe]

Cross Member Added

Okay, I managed to actually do something earlier today. (it's 90 degrees out there now ) Tomorrow maybe I get the engine mounts done...

 

[Lowell]

Looks good to see the wheels on. The dual disc wheel is going up front, right?

Put A/C in your shop, you'll be so much more productive in the summer heat.

 

[safe]

Looks good to see the wheels on. The dual disc wheel is going up front, right?

Put A/C in your shop, you'll be so much more productive in the summer heat.

Good idea... A/C, but that costs $$$. I'm able to get about a half days work done now, but I also like to ride in the mornings too, so it's hard to squeeze it all in before the heat shuts everything down. I'm in no big hurry to finish the project, it will get done eventually.

The dual disk goes up front... those are both front wheels, I don't have the rear wheel built yet, so I needed something for the picture.

Kind of the ultimate "Deltabox" design huh?

 

[knightmb]

The dual disk goes up front... those are both front wheels, I don't have the rear wheel built yet, so I needed something for the picture.

Kind of the ultimate "Deltabox" design huh?

Single disc in the back? Makes sense as you don't want a hair trigger that will lock the back wheel by mistake. Cool pictures, nice to see things in their development building phase. Will make a great before and after pic, just the before pic would be a big pile of parts and some welding equipment

 

[Lowell]

You could use a water cooled unit. Or for the super ghetto low buck a/c, use old car radiators with the electric fans still attached and run tap water through them.
Not sure how the grow-op business is out your way, but around here so many grow ops get busted that you can pick up the equipment cheap at auction.

http://www.ctv.ca/servlet/ArticleNews/story/CTVNews/1122246239835_36/?hub=Canada

While Asians and Vietnamese are increasingly growing the pot, outlaw biker gangsters are brokering it, Indo-Canadian gangs are transporting it and white-collar criminals are laundering the money that injects about $7 billion a year into the province's economy, he said.

 

[CGameProgrammer]

A rear brake isn't even necessary. Motorcycles typically use a small disc in back and a much larger disc in front, the primary brake wheel.

 

[safe]

The Plan was:

Front - Dual Disc Brakes (large rotors 180mm)

Rear - Single Disc Brake (small rotor 160mm)

 

[safe]

Drill Sanding Tool

Today I tried out the drill sanding tool that I mentioned previously. Basically its a simple enough idea... you weld a few spare tubes together and add a drill bit attachment on one end. At first I just put the drill tool into the frames square tubes without sandpaper and spun the tool for a while so that it was metal to metal scraping the worst of the jagged edges off. Then I put on some special sandpaper that has cloth on the back rather than paper. It costs a little more (like a dollar) but it means that the sand-cloth (emery cloth) doesn't fall apart as easily. After sanding for a while the insides of the frame is already quite smooth. I've still got other welds to do so my guess is that more sanding will be needed before I get to painting it. Since there are holes in the frame I'm planning to try to spray the paint inside so that what small bumps remain will be smoothed over by paint. In the end it should be okay to run the "D" cell batteries without too much worry that they will be damaged by the frame itself. All the holes will also help to cool the batteries, which for NiMh is apparently a big issue. (I haven't bought the batteries yet)

 

[Lowell]

This is a much neater and easier way:
http://www.ezburr.com/

 

[safe]

Seat Suspension

Today I got started on the seat suspension. I figure the motor mounts are best left until later. Here's some pictures of todays changes. Basically all I'm doing is adding a top tube that is suspended from the front of the bike. So today was just cutting/grinding of that front swingarm pivot. The final top tube will be a few inches shorter than it is now and will spread out into a "Y" shape at the back. The idea is that the top tube could be used as a "spare tank" with an extra 12V capacity (10 "D" cells) that you could use when the voltage is running low. That way you could run flat out and then when the bike starts to sag you have a way to get home. With NiMh this might not be an issue like it is with SLA, but it's there if I want it. I could also use the extra battery space for some overvolting activity so that I could make special high speed attempts, or even make that my status quo. Who knows at this point... :?

The tope tube alone is about 3 lbs and the shock adds about another pound. When I'm done the entire seat/tope tube will blend into the rear fairing and that will add probably another 5 lbs. So in the end the frame starts at about 17 lbs and adds about another 9 lbs which brings the total up to about 26 lbs. The front fairing would add another 4 lbs or so and that brings the total overall to about 30 lbs. The motor is 10 lbs and the batteries are 30 lbs, so then we are at 70 lbs. The other components like wheels and tires add another 10 lbs, so the final total should be in the general neighborhood of 80 lbs. My current bike is 140 lbs, so from my perspective saving 60 lbs and getting better performance is an improvement...

 

[safe]

Top Shock Mount and Front Pivot

Today I got the front pivot for the seat welded to the frame. I then improvised some mounts for the shock so that I could test the leverage and get a rough idea where to weld the top shock mount. I made the top shock mount have four positions spaced one inch apart so that I will be able to fine tune it's behavior while testing. Tomorrow I'll see about the lower shock mount which is a more complicated issue because I'll be establishing the ride height.

Ignore the forks and handlebars because they are just there so that I could get a feel for how the seat will work with the shock mounted. I threw some rags on the top tube and sat on it. Not something that I would want to ride that's for sure.

Between the four top shock mounts and I plan to have four on bottom and the preload adjustment I should have plenty of adjustability. In the highest preload and furthest back position it's virtually a rigid seat. In the other extreme it's a loose pogo stick. It turns out my mountain bike Fox Shox has a different hole size for the mounts, so I'm not even going to bother with it. All I want is a very small amount of suspension... like less than an inch... and probably with a large amount of preload since without dampening you would find yourself bouncing a lot well after a bump has passed. Having the preload set really high means that only the big bumps give any shock travel... the only way to go when you lack dampening.

 

[safe]

Rising Rate or Falling Rate?

Normally you want a small amount of rising rate suspension. What this means is that you want your shock geometry to make the first part soft and the later part stiffer relative to a linear shock. "Rising rate" means that the shock rate (the amount of pressure applied to the shock) rises as you go deeper into the suspension travel.

Well that's all well and good if you have dampening...

When you lack damping you want to avoid suspension travel when the bumps are small and allow them when they are large. So it's probably better to use either a linear spring rate geometry or a "Falling Rate". In the "Falling Rate" you get the opposite where as you increase your shock travel it takes less pressure compared to a linear rate to compress the shock.

So I'm probably going to want a small amount of "Falling Rate" geometry and a high prelaod. The result would be that most of the time the bike feels like a rigid rear end, but when you hit a really big bump you get some pretty long travel. So it's an "all or nothing" type of suspension setup.

The other option is to buy an expensive shock absorber and do it the other way around.

You might be able to get "Rising Rate" or "Falling Rate" by angling the shock either forwards or backwards. (???) If the top is angled forwards then it becomes "Rising Rate". (it begins perpendicular to the top and ends at an angle) If the top is angled backwards then it becomes "Falling Rate". (it begins an and angle to the top tube and then approaches perpendicular as the suspension moves)

So having four options above and below will expand my options a lot.

Take a look at the picture. Correct me if I'm wrong... but I'm pretty sure I have the angles matched to the rates... it's been a long time since I've thought about this... :?

Also, the angles of the pivots are important too, so it's one of those "hmmmmmm..... how does that work again?" situations...

Seems to me I need to consider the angle that the force is applied...

 

[Lessss]

Eill this one have mud guards? Man I need to learn to weld.

 

[safe]

How about these for "Rising Rate and "Falling Rate"?

This is closer to my real situation which is sort of upside down compared to the usual suspension situation of a swingarm moving upwards. My seat shock swingarm goes downwards towards the frame.

(and yes, Lessss, you need a welder)

 

[Miles]

Why not use an elastomer spring, which will have a higher internal damping?

 

[safe]

Why not use an elastomer spring, which will have a higher internal damping?

I already own these damperless shocks (I bought three bikes with them and have been cannibalizing the parts) and all the pivot accessories. I've literally chopped the first frame up into pieces and reused just about everything.

Ideally I'd get a nice shock like my Rock Shox and use it. I can always upgrade later... even if I have to find some spacers that would adapt one hole size to another to get it all to fit.

Basically, at this point, I don't want to spend any money yet. My last bike was originally produced for about $600 and by now I've spent about $900 with all the extras/repairs/changes. For this new project I'll probably start off closer to $800 (since the batteries will cost more) and go up from there. So it's money.

 

[fechter]

I don't think damping will be a big deal for a seat suspension. Your legs will naturally dampen things since your footpegs will be on the frame. A little bounce won't affect handling as much as it would for a wheel suspension.

You might consider some rails with multiple holes for mounting the shock. This way you can experiment with the position and rate without re-welding. What if a fatty wants to ride your bike to escape being rendered into diesel fuel

Another idea might be to use some kind of air bag or air shock that can be adjusted by the air pressure.

 

[TechBikes]

What if a fatty wants to ride your bike to escape being rendered into diesel fuel

LOL Fechter, you really can't get those images out of your head!

 

[safe]

Bottom Shock Mount

The top shock mount has four bolt locations. The bottom shock mount also has four bolt positions and the bracket is isolated from the frame by two bolts that will allow very precise ride height adjustment.

I think I've covered about every possible situation...

(those things on the bottom will be welded to the frame directly)

 

[fechter]

That's what I was thinking of. :wink:

 

[Ypedal]

Nice work Safe! keep the updated comming !

Your NIMH pack, do you know wich cells you are going for ? with D cells you need to keep the amps below 20.. F cells would allow more.

To protect the batteries from metal wear and shorts i've resorted to thick plastic with holes drilled.. and also Tool-Box liner material ! ( perforated and very tough and spongy.. )

How large is the ID of those square tubes ?