Ebike front fork question

vtbiker

vtbiker

10 µW
Joined
Apr 25, 2008
Messages
5
I'm building a commuter ebike in Vermont. I'm using a high voltage (72v 20ah) and a heavy motor (x5303) and I'm wondering if I can put it on a road bike I have. The frame is sturdy. It's a Raleigh Competition from the 70s built out of 531 steel. The only problem is I think I need a different front fork for the motor. I don't trust the spindly little thing that I have now. Does anyone here know of a place I can get a front fork that is wider/heavier but has the long top-end that would fit a road frame?

I'm pulling the batteries in a one wheel Bob trailer so I'm not worried too much about the amount of weight on the frame itself. I think the bike will work for a summer commuter as long as I can replace the front fork . . .

all the best,
Walker Blackwell
 
72V and 20 amps is mild IMO. If the front forks are steel you should be OK. I run 72V (84V at top charge) and 30 amps on the cheapest steel bikes I find (target -$60) or bikes left by a dumpster.
20 amps is wimpy for that motor anyway and you may blow the controller under load.
Test test test.

cheers
K
 
The batteries are 2 36v 20ah LiFePo in series. The controller can handle up to 50+ amps out with the best mosfets from ebikes.ca so I'm not worried about power. I don't think I would ever be needing to pull more than 30 amps through the system anyway . . .

I guess I can get a suspension fork with a custom steering tube length . . . . .

all the best,
Walker
 
walker,
your head tube is 1 inch threaded, rather than 1 1/8". This size would allow you to run many of todays modern rigid forks design for 29" mountain bikes...

since you don't have it, you should look for an old tandem front fork - 1 inch threaded...

i would recommend selecting a bike better suited for the 5303, particularly front drive..

Peace,

len
 
Walker, sounds like an interesting project. I never miss an opportunity to put in my $0.02 worth concerning trailers. I converted an older style BOB trailer to a power pusher by swapping out the 16" fork with a 26" fork from a cheap Wal-Mart mountain bike. One of the nice benefits was not having to modify the bike, with the exception of adding a throttle. I have a 20" WE BD36 on the BOB trailer. Now that I have lighter LiFePO4 batteries, I have put another WE BD36 on the front wheel (of my recumbent) with the 20# battery on the rear rack. It is a little more fun for just running around, with about 30# less weight and only two tires on the ground. However, I plan to make up a couple of adapter cables, one for the throttle and one to parallel the batteries, so that I can use the power BOB trailer along with the front wheel power recumbent on longer camping trips.
 
vtbiker said:
I don't think I would ever be needing to pull more than 30 amps through the system anyway . . .
Click to expand...

Hahahaha! Stop it you're killing me there! I think every single person on this board has said that at one point or another. :wink: :lol:

Where in VT? I miss Church St. in Burltown... lived there for about 9 months... the coldest 9 months of my life I might add and that's saying something coming from a Montana boy. If it weren't for Nectar's and Club Toast I don't think I would have survived! :wink:
 
If i lived in Ameeeerica it would have to be Montana or Dakota in a Tipee they are THE coolest sounding names ever imo...p.s I would also change my name too "Moves with Wheels" and find me a squaw :p Just like in the western movies :)

carry on...

OH suspension fork would be a good investment i think
 
vtbiker, I'm curious as to why you choose a 5303 front hub, rather than a rear hub? :roll: For about the same cost as the new front fork :shock:, the rear hub is only $30 more and will give you better performance on climbs, and towing, than the front hub will.

Blessings, Snow Crow
 
The reason I got a front-hub is

1. More flexibility with multiple bikes. (Winter, Summer)
2. I can take it off and have a normal bike. (That's why I have a bob trailer for the batteries as well.)
3. I have power going to both wheels. I will be getting a speed-hub in the back that will give me a few extra watts of human power at high-speed in the back and give me a bit more traction in wet conditions. This is just stupid theory, but the first two reasons are the most important.
4. I can use the motor on a delta velomobile in the near future.

take care,
Walker
 
30amps at 72v is 2160 watts, right? How much have people been running through their x5303s? More than 3000? That's a bit much, no?

Anyway, I will get a suspension fork and let you all know how it works out when it all gets done. I though about adding the motor to the bob trailer but I just don't think it will have enough weight on it for hill-climbs. I will add boost batteries to front panniers if my front-motor needs more weight as well . . . 72v 20ah will not quit get me 50 miles over Vermont hills by my rough calc. Maybe . . . with the right tires and BrainDrain settings . . . but who knows. My goal is 25 to 30 mph with pedal (thus the speed-hub.)

all the best,
Walker
 
vtbiker said:
30amps at 72v is 2160 watts, right? How much have people been running through their x5303s? More than 3000? That's a bit much, no?
Click to expand...

Well... I was just joking around. Ebikers alway want more... more amps, more volts, more batts, more speed etc. etc. And yeah, a lot of people here are putting a LOT more than 3,000 watts into their 5 series. :mrgreen:

Anyway... didn't mean to offend or anything.
 
AussieJester said:
p.s I would also change my name too "Moves with Wheels" and find me a squaw
Click to expand...

I have an acquaintance whose last name is Running Crane. Seriously. :)
 
vtbiker said:
1. More flexibility with multiple bikes. (Winter, Summer)
2. I can take it off and have a normal bike. (That's why I have a bob trailer for the batteries as well.)
3. I have power going to both wheels. I will be getting a speed-hub in the back that will give me a few extra watts of human power at high-speed in the back and give me a bit more traction in wet conditions. This is just stupid theory, but the first two reasons are the most important.
4. I can use the motor on a delta velomobile in the near future.
Click to expand...

Using a front hubmotor avoids changing the existing rear drive. This means you can use a internally geared hub, or a cassette on a freehub, and if you have one you don't mess-up your existing rear derailer.

With that said, I do prefer a rear hubmotor. IMO it just feels wrong to put that much weight in the front wheel. It makes it hard to ride up over curbs.

Good luck with your bike, vtbiker. Be sure to use a torque arm, and make sure the nuts on the hubmotor axle are very tight. I recommend you get a wrench for the job; don't try to use pliers or channel-locks.
 
You may find that suspension fork elusive to find, I did. As long as there are no cups on the ends of the dropouts, or you fill them with custom washers, the original fork will be fine. If the oversise washers span the cup, they will tend to spread the dropouts and let the hub spin. 1 mile into my first ride, I did that and fried the controller, as well as learning to pop the covers and wire a motor on the day it arrived. Alloy forks and a front hub are not a real good idea, even with torque arms, and many of them won't allow clearance for the big ol hub anyway. There are a very few bikes out there with a steel suspension front fork that can clear the motor. Look for the ones with the dropout welded onto the tube, and the dropouts mounted to the inside of the tube, not the center. If you want suspension you may have to just go with the bike you find the forks on. Pretty hard to find em loose if you don't have 1 1/8 headset.
 
Hi, first time posting

I've been lurking but this is actually my first post.

So I wanted to ask.
Anyone know if this surley instigator can accomodate a 700c wheel? Description says 26 mtb fork.
http://www.cycle-yoshida.com/motocross/surly/parts/fork/6instigator_page.htm

I saw knightmb's news video a few month ago and now want to build my own ebike.
Seems like he's using a Surly fork but I'm not sure which one.

I currently have: Marin San Anselmo w/ 700c wheels, Topeak MTX, double leg stand
What I want: 4011 clite, 72v 20amp batt, half twist, sturdy steel fork (will i still need a torque arm)

Thanks
 
Most likely not, and definitely the v brake mounts will be in the wrong place. keep googling, about a billion places you can buy a rigid 700c fork. Bikes Nashbar has good prices on a lot of stuff. Have you tried sticking a magnet to your existing forks? they are likely to be steel.
 
artoo22 said:
Hi, first time posting

I've been lurking but this is actually my first post.

So I wanted to ask.
Anyone know if this surley instigator can accomodate a 700c wheel? Description says 26 mtb fork.
http://www.cycle-yoshida.com/motocross/surly/parts/fork/6instigator_page.htm

I saw knightmb's news video a few month ago and now want to build my own ebike.
Seems like he's using a Surly fork but I'm not sure which one.

I currently have: Marin San Anselmo w/ 700c wheels, Topeak MTX, double leg stand
What I want: 4011 clite, 72v 20amp batt, half twist, sturdy steel fork (will i still need a torque arm)

Thanks
Click to expand...

Welcome to here.

26 inch is small by comparison. 700c rim size is called 29 inch when put on a mountain bike. There is a big difference. Occasionally, you can cram a 700c onto a 26" fork. I did with a Roxshox Judy, after substantial grinding and reshaping, but I could only run a 38C road tire on it. The RoxShox also had disk brakes. a V brake setup like that fork would never line up.

A 4011 on a 72V system will put out some torque. at 20Amps, its around 2 horsepower off the line. A 40 amp controller and you'd be pulling as hard as a gas moped. all that force is being put on the tip of the fork at the dropouts. You're going to want torque arms.

Sounds like a great setup, though. Kona and a few others make some Beefy ridged forks for 29" downhiller and free ride bikes. those should work out really well for your Marin
 
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