Safe's Electric Bike Project #003

safe

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The Internet Collaboration Electric Bike

I was riding my Project #001 bike this morning and on the way home I spotted a nice 24" wheel bike that was out on the curb ready to be picked up by the garbage men. I quickly grabbed it and saved it from the sad fate that would have befallen it 15 minutes later.

So here's what I'm going to do. Since I have a welder and can make design changes to the frame I'm going to modify this frame and I'll be taking input from people online. This might be the first collaboratively developed electric bike (at least to my knowledge) ever done online.

:arrow: First let me set some ground rules:

1. The bike was free, so don't suggest expensive solutions... this will be an inexpensive bike.

2. As a design goal I'd like to keep this closer to a normal bike than my other complete "from scratch" projects. Ideally the frame alone will be changed and everything else from the old bike is used. (brakes, derailler, etc)

3. I'd like to keep this one within the "pedals/750 watt/20 mph" rule or at least close enough that it could be crippled so as to obey that format.

I could make more rules, but people will start breaking them from the beginning. Maybe "suggestions" are a better way to put it. :wink:

So here's the frame and it's dimensions: (roughly from left to right)

17.5", 16.5", 13.5", 20", 22", 4.25", 14", 1.5", 39.5"

You can assume that the fairings that I make for the Project #002 bike will be also used on this one. (I'll be making a mold that can produce multiple final copies) It's going to be a "Road Racer" style... that has to be more a less a given for anything I build.
 

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Modification Goal

I put the dimensions into the CAD program and this is how things compare. If I want to use the Project #002 fairings then I need to fit the same basic dimensions as the Project #002 bike. (otherwise I'm starting over which is a bad idea) So this is the basics of how a "stock" frame needs to be redesigned in order to have a decent handling bike at high speeds.

52" is in my opinion the "natural" feeling length that the bike feels best at...
 
One Design Option

This idea to extend the frame has many advantages. First it places the pedals far to the back which is in line with where we want them to be. Second it opens up a big place in the front to install the battery pack. Third it's a "no brainer" thing to do because the existing frame remains the same and so alignment is easier.
 

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that looks pretty good but it might be better to just cut off the headtube and extend the top tube and weld the headtube the extension as well as remove the bottom tube and put in a new one the right length and angle to go to the headtube. in the picture you have it just welded to the existing headtube, i dont know if you just left it in for a quick drawing but if not you would need another headtube and welding to the old one would be a weak link.

like this...
 

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dirty_d said:
it might be better to just cut off the headtube and extend the top tube and weld the headtube the extension as well as remove the bottom tube and put in a new one the right length

Well there's the issue of frame flex too. The modified frame needs to be stronger than the stock frame. So how about this one? This adds extra strength and builds the battery mounting location better. The extra bottom tube would reduce the bottom bracket flex and also make the overall twisting flex go down.

The less "free form" alignment I have to do the better. Having the frame intact allows the alignment to be easier.

Should weight be a big issue? I don't think a few pounds matters that much.

:arrow: Update: Nice photo editing. (very quick)

Another idea would be to simply get some larger diameter tubing (like you've shown) and that way you could span that length and still be rigid.
 

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or get rid of the old downtube and use 2 tubes on the bottom for more strength instead of one like i guess you have in your picture, the side profile would still lookthe same as yours from the side minus the original downtube. it would look like this from the midle line would be the top tube.

just to look cleaner and have more room inside the frame, the 2 tubes on the bottom would make battery mounting easier too.
 

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Battery weight produces new stresses that a normal frame doesn't have to deal with. I like the idea of a simple set of tubes, but maybe they simply need to be massive... like 2" or something. That way you have plenty of strength. The battery could be divided in half and it's okay to go about a full 10" to 12" wide to fit within the fairing. Also the shape could be irregular as well if you used individual cells.

Rather than just two bottom tubes I could build a sort of "space frame" like a Ducati and contain the battery that way. (not shown, but it's an idea)
 

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Also, the motor needs to be moved forward (to increase foot clearance from the pedals) and the chain would go more like this...
 

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what if you move the motor behind the seat post under the rear fairing the chain would be shorter and more out of the way.
 
dirty_d said:
what if you move the motor behind the seat post under the rear fairing the chain would be shorter and more out of the way.

That's how my current bike is setup. It moves weight back and my experience has been that the rear wheel takes too much weight as it is. The more central the location of all your weight the better. Plus, the area in the front is essentially free space. When you add 10" off the front of the bike (extending the steering forward) that opens up a big hunk of real estate that can be used for the motor and the battery. It's exactly where the weight should go too. Road Racer motorcycles tend to place most of the weight forward because they have so much horsepower that they have a hard time keeping the front end down (which for me will not be a problem) but it's also a benefit to handling in that when the rear end is light it can slide and then catch with little problem. Overall I'm happy with the "conventional" weight location for a Road Racer. Electric bikes seem to not really know what to do yet and the short wheebase prevents most bikes from placing the center of mass forward. So think:

" :idea: Long wheelbase... central/forward weight positioning"

Plus, unless you have a really narrow motor you will have clearance problems when you pedal.
 
This idea would be that you use a long rectangular tube from head tube to seat tube. This allows the rear end to flex vertically (soft ride) but the twisting flex (the one that makes the bike feel wobbly) would be much less. If you use two large tubes (like a regular bike) then the suspension feel would be very harsh.

The main stress points would be:

1. Steering head tube.

2. Battery.

3. Motor.

4. Bottom Bracket when pedaling.

By placing just one big rectangular tube in the middle of all four you make sure that the most important stresses (the twisting ones) are eliminated. Everything else (like the forks and the rear end) can be stock and a little mushy.

As an added bonus, this design fits perfectly with the Project #002 bike so things would be more transferable back and forth. (fairings, battery box dimensions, etc)
 

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that looks good but i dont know about any flex, it flexes a little but i dont think it would really feel any softer would it?
 
dirty_d said:
that looks good but i dont know about any flex, it flexes a little but i dont think it would really feel any softer would it?

The main rectangular tube would not flex at all. All the flexing takes place in the upper rear chainstay. There's a reason for having a bike frame the way it is in that the small tubes flex when the bike hits a bump. Forks are also designed to give a little so as to absorb the bumps. When you have small tires (like the racers skinny sewup tires) you don't create very much in the way of lateral forces and so the sideways twisting effect is small. Also, a regular bike only has to deal with the rider and his weight and is distributed on one of three locations:

1. Seat
2. Handlebar
3. Pedals

So for a regular bicycle they calculate the stresses (or go by trial and error) and come up with a good compromise. The time trials bikes are a good example of existing bikes that deviate from the older conventional design. Time trials bikes are much stiffer... and they are not recommend on the longer rides. (time trials tend to be shorter and faster)

The electric bike introduces new stresses:

1. Increased tire width (my 24" x 3" tread as an example) means that you can double or triple the lateral forces at speed. You can go much faster through a corner with big road racing slicks than skinny tires.

2. The motor and battery add a lot of weight in locations that the frames are not always well prepared to handle.

3. The faster speeds on the straights and higher cornering speeds mean that you need to increase the wheelbase in order to make the bike easier to handle. A longer wheelbase means that all the other factors are amplified so you need to compensate for it.

In the end the electric "road racer" that really "performs" as one might want will need to deal with a new set of design principles.
 
Hi Safe,

It's a great idea to have a collaborative ebike project, but if you want people to collaborate wouldn't it be best to stick with a stock frame so that it appeals to as wide an audience as possible and so that people without fabrication skills can replicate it?

Perhaps it would be a good idea to set up a poll (or series of polls) to find out what most people want most. It's obviously impossible to satisfy everyone's idea of the perfect ebike and it would naturally result in a compromise design, but with all the experience here it could be a compromise that works better than most of those on sale at the moment and provides a foundation that people can tweak to suit their own preferences?

So:
Maximum power?
Maximum speed?
Hill climbing ability?
Acceleration?
Weight?
etc. etc.
 
Malcolm said:
It's a great idea to have a collaborative ebike project, but if you want people to collaborate wouldn't it be best to stick with a stock frame so that it appeals to as wide an audience as possible and so that people without fabrication skills can replicate it?

I do like the simple "double diamond" design. You have a strong argument and I agree with it in part. "Collaborative" isn't going to mean a "democracy" in this case. I give more weight to a strong argument held by one than a poll where 50 people vote for something that I don't feel very good about. After all, I'm actually building the thing and I need to "buy into" my own work.

So rather than polls I'm looking for good ideas and like the CEO of a company I want to hear ideas, good bad and ugly and I'll sort through them until I come up with what seems like the best solution.

As you can see I've passed through several design ideas already. One argument for a rectangular "spine" bike is that you eliminate very quickly the flex problems you might otherwise have to deal with. By over designing the mid section you can allow the ends (the fork and the rear chain stays) to flex in their natural ways. Another big advantage is that it becomes dimensionally identical to my #002 project and so I could swap parts back and forth, maybe even be able to avoid buying some things because I only need to ride one bike at a time.
 
Tire Size Difference

I have these 24" x 2.35" road racing slicks that fit easily into regular bike frames and forks. (the 24" x 3" tires would not fit a regular frame or fork and are designed for chopper bikes) So that's one difference between the #002 Project and the #003 Project.

Everything on this bike should be less "severe" and should be more easily buildable with regular parts. (which might mean the stresses are less of an issue because I have no idea yet if these smaller tires give the same traction that the full sized ones do)


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This frame design would go well with a forward mounted battery pack if you extended the wheelbase out to 52". In it's stock form there isn't enough room, but once extended 10" the room opens up.

So the long wheelbase bike solves the question of "where" to place the battery pack. On the normal bike wheelbase you are forced to place your batteries on the bike rack or straddle the bike with saddlebags.

A 52" wheelbase is a "win win" since you get the slower handling and you solve the battery location problem at the same time... :wink:

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@safe: wow, so cool! now if only you cold get it to fold too ;)
 
:?: Has anyone else tried to create a new thread?

I'm getting:

"Sorry, but only users granted special access can post topics in this forum."

...am I being singled out or is this a policy change for the messageboard?

Kinda makes is hard to communicate a clear idea if you can post, but can't "define" your category by creating a new thread.

Maybe they are having technical difficulties?
 
Johnbear said:
From seeing Safe's work, I bet he could make it fold (Either way)! - I would love to be his neighbor!

The way he rides, I wouldn't feel secure walking the streets without a kevlar body suit if I was Safe's neighbor.
 
Renewed Interest

With the colder temperatures making fiberglass work harder to do I'm going to refocus on the welding side of things. I've ordered some:

2" x 2" x 0.065"

...square tubing to act as the main support for the #003 project. This will weigh about five pounds and when you add the other parts the total frame will come in under ten pounds, which is more realistic for a bike that you pedal with. The #003 bike will have the identical dimensions of the #002 bike and will also share the same seat suspension. The fairings will fit on both bikes.

I'm also going to switch to the Threadless Headsets for a pair of new forks that I'm going to make that will use true clamping triple trees. This should make for a very easy to configure set of rigid forks and I'm going to make a pair for the #002 bike too because the forks I've started seem like they are going to be trouble before I've even used them. There are just too many problems with building suspension forks using the primitive tools that I have. (spring rates, axle stresses, sticking sliders, slider slop, etc...)

:arrow: So I'll be posting welding pictures of the new frame in a week or so when the metal arrives and I get started. At least when it's cold you can huddle around the welder for warmth. :wink:
 
You're building 003 when you haven't even ridden 002 yet to work out bugs, and see how it might be improved or altered?

When you get to 007 and the license-to-kill, the neighbors really better watch out. :)
 
xyster said:
You're building 003 when you haven't even ridden 002 yet to work out bugs, and see how it might be improved or altered

What can I say... I ran out of good weather. :oops:

My #001 project worked great and I've gotten 3000 miles out of it, so it wasn't like I went without a ride. And don't forget that I actually got the #001 project just barely working at the end of 2006 and then had to wait all winter before really getting to use it. So I've now gotten enough mileage out of the #001 to feel that it's been fully "completed". (and I'd rate it a "success") But don't forget that it took six versions of the transaxle before getting it right. (that's like a month of work)

The #002 project is pretty close to being ready to go, but I really won't be able to get into the full testing cycle until next year anyway, so I'm holding off buying the batteries until the last possible moment.

If I start the #003 project NOW I might actually even be able to use it next summer... it takes a while to build these totally custom machines... (it's not like I can just go to the store and buy this stuff, it's all custom built)

It's taken Dirty D a few months to build his custom machine and he's using a lot of off the shelf parts to make it work.

Custom bike making is not easy...
 
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