Where do I get fat tire trike hubs?

[kylerlaird]

My daughter says she wants her 20" fat tire e-bike to be a trike. I bought one of the cheap trike conversion axles.

Amazon.com

On the drive side, there's a double-D shaft. It looks like these wheels are made for this application.

20" Fat Tire 20x4.0 Tricycle wheel Trike Wheelset 3 wheel convert kit 15mm axle | eBay

Right wheel is the drive wheel, with one side bearing and one side D shape drive hole. Left wheel with two sides bearings.

www.ebay.com

I'd rather use the front wheels from her bike and her sister's bike (replaced by 750W motor wheels) and just lace them on to the proper hubs. I haven't been able to find the hubs, though. I only found some for thinner wheels. I did see fat tire trike hubs that mate with a 3-hole flange instead of the double-D shaft. It looks like I could buy a replacement axle and do that, but I'd like to see if I can make this design work. Ideally, I'd find hubs with disc mounts, too.

Any suggestions? I'm thinking about building trikes for me and my wife, too, so I'd like to get good at it.

--kyler

 

[Cryingmadman]

My daughter says she wants her 20" fat tire e-bike to be a trike. I bought one of the cheap trike conversion axles.

Amazon.com

On the drive side, there's a double-D shaft. It looks like these wheels are made for this application.

20" Fat Tire 20x4.0 Tricycle wheel Trike Wheelset 3 wheel convert kit 15mm axle | eBay

Right wheel is the drive wheel, with one side bearing and one side D shape drive hole. Left wheel with two sides bearings.

www.ebay.com

I'd rather use the front wheels from her bike and her sister's bike (replaced by 750W motor wheels) and just lace them on to the proper hubs. I haven't been able to find the hubs, though. I only found some for thinner wheels. I did see fat tire trike hubs that mate with a 3-hole flange instead of the double-D shaft. It looks like I could buy a replacement axle and do that, but I'd like to see if I can make this design work. Ideally, I'd find hubs with disc mounts, too.

Any suggestions? I'm thinking about building trikes for me and my wife, too, so I'd like to get good at it.

--kyler

 

[amberwolf]

Note that all the pics on that amazon listing show the kit upside down. When you install it the wider brace goes on top, and the gear cluster on the right.

Hubs for these axles usually use some form of D or double-D hole as the axles usually have flatted axles to match. This one looks like it may use two different axle / hub types, with the driven side (right wheel) being a different diameter on the inboard side where the D or double D hole is, and the outboard side being the same small hole size as the non-driven side (left wheel)


On this kind of conversion axle, AFAICT the left wheel just rolls along on whatever axle bearings it has, and has no braking or drive on that side. All the braking (via the band brake on the axle) and drive are on the right wheel. (hopefully the bike already has a good front brake)

To use disc brakes on the hubs (if you make or find some that have rotor mounts), you'll have to build caliper mounts to bolt to the fender-frame mounts.


Do you have any fabrication skills? If so, you can usually make your own hubs easily enough, or even just modify existing ones that are what you want but too narrow. (if they are steel, you can just cut them in the middle of the tube, then cut a length of new tube of the right length to make the hub the width you want, whose ID is the same as the hub's tube OD, slip them together, and weld or braze them together (just make sure you line up the spoke holes in the flanges the same as they were before).

(it's possible that a good epoxy, coating the OD of the hub tube and the ID of the new tube, before slipping them together, might even be enough to secure them, if all the loading is handled by the flanges to the axle and the tube just connects them).





BTW, whatever it's speed was as a bike, as a trike, it could be a good idea to limit it's speed to around 15mph or even 10mph or less--in my experience with the geometry you can end up with on this kind of conversion, it is likely to tip over and crash at the slightest twitch of the handlebars before you can even react at higher speeds than 15mph, and is likely to be unstable and hard to control above 10. Sometimes even 10mph is too fast.

Hopefully yours won't have this issue; since there's no info on what bike is being converted, there's always a chance it could turn out better.

The lower the COG is, the better, and the more weight is on the outboard points of the rear (at the wheels) the better, but both of those are hard to do with that style of trike kit and when converting a bike into a trike.

Another issue is the steering; trail / caster on a bike is different than what's needed on a trike, and sometimes the one just doesn't work like you need it to on the other. It's possible to change this by changing the fork, or sometimes other methods, to improve handling if necessary.

Any suggestions? I'm thinking about building trikes for me and my wife, too, so I'd like to get good at it.

If you're going to build trikes, I recommend taking a look at my SB Cruiser thread. It performs and handles well up to the 20MPH speed limit we have here, and if you were building one from scratch you could make a few improvements to the design that I've never gotten around to on mine because I use it every day and would have to take it out of service to do (like rear disc brakes).

There are a series of versions of it that have different looks and usefulness for different kinds of operation.

There are many other kinds of trikes, too, depending on your needs, usage, and skills.

 

[kylerlaird]

Good advice. Thank you!

BTW, I bought another kit. This one comes with 20" (not-fat) wheels and it has a "differential" (which I suspect is just an overruning clutch. Its axle doesn't seem to bind as much. The axle drives the hubs through plates that cup around the Allen-head screws in the hubs. Yet another variation that I can't find hubs for...

 

[kylerlaird]

Here's how it stands now. It is far from ideal.

It has disc brakes all around. I was thinking of putting hydraulic brakes on the back and splitting the fluid. Now I'm thinking of just using cable brakes for the back and regen for the front.

 

[amberwolf]

Depending on the split method, cable brakes are relatively easy to adjust to give symmetric braking forces; I don't know about hydraulics (other than at the caliper by adjusting the pads).

You can get cable splitters to use a regular lever to pull two cables, or you can get two-cable levers to individually pull the cables at the same time, and each cable has it's own adjuster on the lever.


If it's just an overruning clutch then AFAICR the faster wheel (outboard) in a turn will not provide any thrust, it will just be freewheeling. (might be the other way around; too tired to be sure).

 

[Papa]

Here's how it stands now. It is far from ideal.
View attachment 337433

As Amberwolf alluded to, motorizing trikes akin to yours, is strongly discouraged.

1. CoM (Center of Mass) is dangerously too high. Tipping (while turning or stopping) at speeds much above 5 mph
is almost guaranteed. Adding mass (such as a front hub motor) shifts the CoM forward, exacerbating the condition.
2. Wheelbase is too short. As speed increases, steering becomes extremely sensitive.
3. Weight Distribution range is almost nonexistent. Ballpark, should be 33F/66R.
4. Rear track is too narrow. 32" or more is encouraged.

The trike below is one I built over a decade ago. Designed top speed just under 30 mph (Idaho moped limit).

 

[kylerlaird]

I put this together last night. Short wheelbase trike, narrow, motor up front. It's quite a reasonable ride; definitely not like my Kettwiesel, but surprisingly adequate.