700c fork recommendation?

[oatnet]

I have a front 700c 5303 wheel with (2) torque bars that I bought from cgameprogrammer a few month back. Ordinarily I would avoid front hub motors but this is going on a 'special' demonstration project that is more spectacular than practical.

Anyhow, I need a 1 1/8" 700c threadless fork to mount the wheel on - what would you guys recommend? The stronger, the better - this bike will not get run often, but it will get run hard.

-JD

 

[Ypedal]

If you like your teeth attached to your skull i'd suggest mabe considering a custom fork, got any good welding shops locally ?

I have looked into it and a custom bike fork by a bike builder = aprox 400 $... A welding shop that has the materials would likely make one for less but it's a hard call..

What voltage ?

 

[Ypedal]

http://endless-sphere.com/forums/viewtopic.php?t=1919

See bottom of this page..

I would not go over 48v on this fork, i looked on ebay, called the local bike shops, etc.. before i even took the original wheel apart.. i was unable to find anything " Beefy " enough to make me happy...

Knight is running 72v on a 406, but it's a far cry from a high-powered X5.

 

[CGameProgrammer]

I had bought a fork from a now-defunct company called Katy as far as I remember. It was still too narrow for the brakes to fit, though. A custom-made fork is a good idea.

Keep in mind forks for 29" wheels will work as well, and they may be wider too. 29" rims and 700C rims are the same diameter, though 29" tires are about an inch thicker. The larger size of a 29" fork would be good, and it might let you fit brakes on too.

 

[knightmb]

Knight is running 72v on a 406, but it's a far cry from a high-powered X5.

Yeah, 72v @ 20 amp max controller for safety. It's enough to do silly things like peal out, but not enough to rip out the front fork. I'm using a torque arm on mine as well and the forks are sorta beefy mountain bike forks with shocks.

This fork in the pictures below is a solid steel 700C shock corrected (if your 700C had shocks on it, this will make them the right length so your bike doesn't slump forward). It's a spare one in keep in case I destroy my front fork again. So far, the new torque arm has eliminated my fork trashing problems, so I'm more than happy to part with this one if anyone wants to buy it for an e-bike. I can say from experience that it can handle a 406 up to 60 volts @ 20 amps without giving. At 72 volts, that's where it can break out of it. But you won't have a shatter failure, just a bend failure. That's why I've survived all these broken forks.

 

[oatnet]

Wow knightmb, "shock corrected", I didn't even think of that and I would have been disappointed, Thank You!

Cgame - I'll go look up Katy - definitely gonna need brakes though.

Gaston, 72v, amps I am unsure of.

Here is what I am thinking - a 2-wheel drive bike; impractical but perhaps gimmicky enough to catch the eye of the local news when I start sales.

I have that 700c front 5303 and a bunch of 26" rear 5304/5305. Earl sells a controller that handles two motors (no I am not confused with the dual-speed controller) up to 72/20 but since each wheel only sees 1/2 the amps it they will only see 10amps... I'm gonna see if it can be made to 72v/40a so they will see 20amps at launch.

Here is what I envision:

1) The torquey 5304/5 will bear the brunt of the launching load reducing the "shock" to the front forks.
2) At middling speeds both motors will share the load.

3) At higher speeds backemf on the 5305 will reduce how much current it can draw, increasing the current available to the 5303, gradually increasing the torque pressure on the fork.

4) At top speed the 5305 will be practically freewheeling at very high effeciency and the 5303 will be drawing most of the current (be it 20a or 40a) in its best range.

I am hoping that the tall "gearing" of the 700c, plus the lower launch torque of the 5303, plus the low watts at launch, will reduce the impact on the fork.

As a result, I should have tons of low-end torque and I _MIGHT_ be able to break the 50mph barrier at 72v. This wouldn't the safest bike - but it would only be for exhibition and display. Sure, there are other ways to get there - 104v etc - but I think the gimmickry of 'All Wheel Drive" will call attention to the idea that ebikes aren't just toys anymore, they are a commuting alternative. Doing a face-plant on a split fork would not send the message I had in mind .

I am sure the old hands on this board have seen others do a build like this, and I hope you will share your wisdom with me.

-JD

 

[Rassy]

Sounds interesting. When I decided to put 3 hub motors on my trike/trailer combo, I went just the opposite, using 3 identical motors, 3 identical controllers (so each motor could get its 35 amps), and all feeding from the same battery pack (36V x 36AH). Figured if all three motors were trying to do the same thing at the same time they would enhance each other the most, and it is working out very good.

However, your arguments sound good, and will be looking forward to seeing your final results.

 

[xyster]

4) At top speed the 5305 will be practically freewheeling at very high effeciency and the 5303 will be drawing most of the current (be it 20a or 40a) in its best range.

As the 5303 is passes the top speed of the 5305, the 5305 will begin regenerating current, causing it to brake. There may be other problems with simultaneously employing motors with different windings....

motor experts: what say you about oatnet's idea of using two hubmotors with different windings concurrently?

 

[knightmb]

As the 5303 is passes the top speed of the 5305, the 5305 will begin regenerating current, causing it to brake. There may be other problems with simultaneously employing motors with different windings....

motor experts: what say you about oatnet's idea of using two hubmotors with different windings concurrently?

Good question. Seems that the regenerating current would simply go to the faster 5305 instead. But I know you can't create more energy than you use, so maybe instead the effect will be basically what he said, the current will turn over to the faster motor and the slower one will become moot until the speed lowers to a point in which it can play a part. This will be a very interesting experiment, none the less.

 

[monster]

just make sure you have a nice smooth runway to test it out on. if you hit a bump on a 700c wheel at 50mph -your a corpse!

i'll love to try it though, just once, to see how fast.

 

[Drunkskunk]

the point were the 5305 will start to act as a brake even under power is fairly high. its not the top speed of the unloaded wheel, but the theoretical top speed of the wheel, turning in a vacume at 100% efficancy.

since most of these motors are only 50-70% efficent, then you can figure speed were the turnover happens faily easily. If, for example, the 5305 will run the bike up to 40mph on it's own, then the braking effect would be somewere around 60 to 80mph. any speed below that, and it will still be adding some thrust to the bike

 

[xyster]

the point were the 5305 will start to act as a brake even under power is fairly high. its not the top speed of the unloaded wheel, but the theoretical top speed of the wheel, turning in a vacume at 100% efficancy.

since most of these motors are only 50-70% efficent, then you can figure speed were the turnover happens faily easily. If, for example, the 5305 will run the bike up to 40mph on it's own, then the braking effect would be somewere around 60 to 80mph. any speed below that, and it will still be adding some thrust to the bike

The 5305's no-load speed at 72v in a 26" wheel is 43mph:
http://www.ebikes.ca/simulator/
I don't understand these motors well enough to give a technical reason, but it just seems like running two different winding type motors simultaneously from two separate controllers is going to cause the slower motor to drag enough to prevent the realization of any gains that a 2WD system otherwise might enjoy. Part of the reason I think this is my experience pedaling my 5304 compared to my free-wheeling' Currie ebike. The cogging torque becomes very noticeable above 10mph; I can't pedal it much faster than 12mph for more than about a quarter mile. I can pedal the Currie 18mph over the same distance. But going slow, below 10mph or so, there's not much difference pedaling the bikes. The X5's pedaling drag increased noticeably after I changed from a 24" to a 20" wheel -- presumably because the motor is spinning faster in the latter.

 

[oatnet]

The 5305's no-load speed at 72v in a 26" wheel is 43mph:

Yeah, I have been thinking more about the 5304 since it will no-load at 54mph. Between the two motors I should have more launching torque than the 5305. If I can upgrade the dual controller to 104v the 5305 would no-load at 63mph and be a sweet option.

I don't understand these motors well enough to give a technical reason, but it just seems like running two different winding type motors simultaneously from two separate controllers

Single controller, designed to power 2 hub motors (not the dual-hub motor) originally intended for tricycles.

The cogging torque becomes very noticeable above 10mph;

Hmm... I had envisioned about the torque from these two motors as being cumulative, not competing for a particular set speed and fighting each other. I expect that one motor will always be working harder than the other, but they are both pushing forward towards the same goal. I haven't noticed this cogging torque effect on my TF's or the x4's I have been testing, but I am just starting to test the x5's so I will look for it. At any rate, this could be an interesting experiment.

-JD

 

[Ypedal]

I'd run 2 seperate controllers, with 2 seperate throttles !

That's gonna drain a pack .... FAST...

 

[xyster]

I'd run 2 seperate controllers, with 2 seperate throttles !

That's gonna drain a pack .... FAST...

Not necessarily. Like extra voltage decreases amps needed to go the same speed, whether or not your batts drain faster running two motors depends upon whether and how you use the extra available power.

Do you think two 5304s, each running full-out 72v 40a uphill, would drain the batteries faster than one running 72v 80a ? The extra 25lbs may slow the dual system a little, but two motors running cooler than one may cancel any weight effect.

 

[knightmb]

Do you think two 5304s, each running full-out 72v 40a uphill, would drain the batteries faster than one running 72v 80a ? The extra 25lbs may slow the dual system a little, but two motors running cooler than one may cancel any weight effect.

I was about to say, it's better to spread the load among two motors that only work half as hard, than one to work twice as hard. Given of course we aren't considering how hard the batteries will have to work to power one or both at that voltage/current level.

I would hazard a guess that two motors would be more efficient only because heat is waste and less heat means less waste. Of course, the main question is, "Did I save enough power to offset the extra 25 lbs" and that one would be hard to use a thought experiment on for me.

 

[Rassy]

From what I've read, the WE BD36 is a pretty low end hub motor. However, with three 20" hub motors pushing/pulling over 400 pounds using 36V x 36AH sla the 0 to 20 MPH non-pedal time is about 5 seconds. If I had any desire or need to increase either top speed or torque I would upgrade the battery system, and controllers if necessary, but not the motors.

Anyway, based on my experiences and information gleaned from here, a great high performance and versatile bike would have a front and rear hub motor plus a third hub motor on a Bob style trailer, all matched. The batteries and "groceries" would go on the trailer, leaving the bike to look and feel like a "real" bicycle. It would be interesting to figure how light this could be, with small motors, aluminum frames, and light batteries. Almost makes me wish I was younger, and I would do it (but I like my heavy trike). My goal would be 35 MPH top speed at 48V with a range of 100 miles at 20 MPH without pedaling.