Fork and Rim question

[mimoose]

Hello. I need help with two questions. I am pretty much completed welding the frame of a recumbent delta trike.

I decided to go ahead and get a hub motor now. I got it two weeks ago. 36volt. I will be using SLA batteries until i can save up for a Li battery set. i have no experience with at all with hub motors and i didnt realize the size and weight.

I now know that none of the 5 fork options I have will work. Those fork i had chosen before when i was going to used a regular wheel no longer work with a hub motor wheel. they are either not wide enough or the drop outs are not heavy enough or its aluminum or i need to and tabs for disc brake adapters.

There seems to be a consensus on this forum that front hub motors should not be used or are not as good as rear hub. but a rear hub motor is out of the question for this trike build as is mid drive, so I need to build as strong a fork as i can and hope for the best. and that way I can add all the things i need;the right width, drop outs at least 1/4 thick, disc brake tabs. I am thinking of the triple tree rigid fork. I have not built a fork.

I used to have plans for chopper forks a while back, but i lost them when a hard drive died on me and the link is long lost. If anyone has a link to triple tree plans, please pass it on.

i am considering these chopper legs i just came accross http://www.bicycledesigner.com/bike-parts/bicycle-forks/42-chopper-fork-legs-with-caliper-mounts---raw-metal.html but not sure if the drop offs/drop outs are thick enough. the trees listed on that site are not wide enough.
anyway two questions;

1. Which rim should i use for the front wheel? I have a wide, steel 24 inch rim[/size] or this aluminun rim with Triple-box construction ,which is used for pedicabs
http://www.amazon.com/SunRingle-Rhyno-Lite-Silver-Presta/dp/B001CJVGGK/ref=pd_sim_sg_5
the rear wheels are 26 inches.

2 What thickness should the metal of the fork Fork Leg tubing be? And I was thinking of reinforcing the tubing inside.

Thank you!

 

[Drunkskunk]

Nothing wrong with front motors. they have thier uses. they do need some extra caution with the forks though. Aluminum and suspension forks are a bad idea, and shouldn't be used. And the front motor does have some limitations, but also some advantages.


Don't sweat the front fork too much. A standard steel fork is going to be plenty strong enough unless you're on some high speed off road racer, or plan to make a heavy cargo bike out of this thing.
The important part is the dropouts. they need to be strong enough to resist the twisting forces of the axle. Making some out of 1/4 steel should be enough for a 36v motor.
I welded a thick set of dropouts to an 80+ year old set of forks from an antique Columbia frame. I've been running that thing since 2009 or so. Works fine.


As for the rim, that Sun Ringle rim is fine. the Rhynos are a good rim. but it does depend on where you plan to ride. Off road and with some weight on them, I would run the Sun Ringle MTX instead. but on road and for 99% of the world, the Rhyno is a great choice.

 

[d8veh]

I've fitted loads of front motors to bikes. Nearly all had aluminium forks. Up to 350w, use one torque arm; over 350w, use two. It's very important to fit the motor, washers, wheel-nuts and torque arm properly. Disc-brake forks are the best because they have a secure anchorage for the torque arm. For aluminium forks, I'd say that 48v with 25 amps is about the safe max. After that I'd want to do some strengthening or use steel ones.

 

[dogman dan]

I think you are sweating the fork too much. It should be easy to locate a standard steel non suspension fork that can run 1500w of power, like a 48v 30 amps controller would provide, as long as you have two torque arms installed on the motor.

I would trust a standard cromoly fork much more than anything I made. But then again, I weld for shit.

If you are looking at suspension forks, that is a whole different can of worms, but it can be done. I rode at least 6000 miles with aluminum suspension forks and a 1200w front hub motor setup.

Whether you choose alloy forks or steel, the key thing is using a torque arm, or two if running more than 800w or any wattage on alloy forks.

But, you will find that many suspension forks do not have the clearance for the motor. So it can be a bit tricky to use suspension forks, and even when you find one that fits, they don't always work well with the motor weight, or with the motor pulling forward.

As for the rim size, for starters, you get a whole lot better range of tire choices easy to find in 26". But the real question is what does 24" vs 26" do to the head angle of your bike. You don't want to fool with it much more than 50mm either way, or it will start to really change the handling. I have no clue what a good head angle is for trikes. Is it even similar to bike?

 

[mimoose]

Drunkskunk, d8veh, and dogman, thank you very much! I am actually quite relieved about going forward on this fork issue. Definitely all steel. i am going to have to forget about the suspension. So far all the rigid forks or trees that have been avaliable where 4 inches, and i need it wider because i ordered a disc rotor mount on my motor so i need 4.5 inches or more. i can also make and weld some torque arms on as well. I know a professional welder who has already done some work for me to weld it together after i have spot welded it. I can weld it myself, but i dont want to take chances.

 

[DAND214]

Did you order a front or a rear motor?
A rear is about 135mm and frt are 100mm. Disc brake shouldn't make it wider if it's a standard hub motor.

Dan

 

[mimoose]

my metric ruler reads fork that is wide enough as 110mm,
the english ruler reads it as just under 4.5 inches. the disc brake mount adds 15mm.

Did you order a front or a rear motor?
A rear is about 135mm and frt are 100mm. Disc brake shouldn't make it wider if it's a standard hub motor.

Dan