How do you build tadpole front wheel mounts?

[parajared]

I am welding up a trike using a $12 thrift store BMX and a bunch of junk I have laying around the garage. It has been really fun so far, but I am wondering how you homemade trike builders make the front wheel mounts.

I am specifically interested in how the wheels anchor to the frame and still steer.

My KMX trike was presumably built by a wizard as there is no way they could have welded the mount on without melting the bearings too.

Anyone know how to perform such sorcery?

 

[bowlofsalad]

That is the hard part. Perhaps he used an excellent heat sink. I've seen videos of materials that are like puddy that will keep the heat away from the surface beside it even if you are using a blow torch getting the entire surface glowing hot red.

I don't know if this forum is the best place to ask this question though. I doubt there are many fabricators here. Atomiczombie or weldingweb would likely have a far larger pool of people with deep wisdom on this subject.

I've considered using entire suspension forks and all kinds of various designs for making a tadpole trike but that one part seems pretty tricky.

 

[MadRhino]

There is something I don't catch.
I am not a frame builder, and I don't know much about trikes...
But my logic is hurt. Why would you want to weld a part that has a bearing in ?
IMO, bearings are inserted and components assembled after the frame is welded, polished, even painted.

 

[Drunkskunk]

I can't imagine any part that would need to be welded with a bearing still in it.

I think the BMX axles will be small, and aren't going to take any serious abuse. they are ment to be supported from both sides, and supporting them from just the far end of one will make them many times weaker, but it's been done before. With no front brakes, its easier to design something that will work.

On a normal trike, the axle is part of the bike frame, not the wheel. when you remove the wheel, you pull the hub off the axle. They use a lot thicker axle that can be supported from just one side.

Here's a youtube of some random guy who built one.

[youtube]oyZWC1PeReA[/youtube]

 

[docnjoj]

These guys have an interesting way of supporting both sides of a trike axle.
http://lightfootcycles.com/trike-models-overview/

Our trikes use 12mm SS bolts and seem fine with the cantilever.
otherDoc

 

[llile]

We've struggled with this detail over the years, and come up with three different methods:

1. Buy or commandeer wheelchair hubs. They are specifically made for side loading. Spoke up a wheel with them.

2. Get a 1/2" Grade 8 hardened bolt. Take apart a 20" bike wheel bearing, take out all the guts, and drill it out carefully until the 1/2" bolt goes through. You can do this without destroying the axle on the right brand of wheel. Drill out the cones and other bearing guts so the bolt goes through them as well. Slip the 1/2" high strength bolt through the whole assembly including bearing cones. Then thread it through a hole machined into an aluminum block, with a nut on the other side. The aluminum block has to be on a vertical axle which we will "leave as an excercise for the student to design" as they say in the textbooks. Ride it around the block. Notice how the left side comes unscrewed. Now grind a slot in the bolt, and fashion a pin or cotter that can keep the nut from coming loose. Drill a hole in the nut for the cotter if that will make it not spin. Castle nuts might work too. Locktite won't cut it nor will nylon insert nuts or jam nuts. 1/2" hardened bolt may also work on an internal brake hub, which a friend successfully built. Hasn't broken the bolt in ten years of riding, although he's destroyed spokes and wheels. Don't forget to

3. You can use a rear hub motor with a heavy axle supported only on one side, if you clamp it hard so it can't rotate. This would be for a two-front-motor design. I'm working on a build like this now. Gets pretty complicated, probably not for the lighthearted.

 

[amberwolf]

Also see http://packratworkshop.com

 

[parajared]

We've struggled with this detail over the years, and come up with three different methods:

Thanks llile, I went with method two

I decided the way I wanted to build them was to leave a hole in the middle of the wheel and weld a big fatty bolt to where the shocks usually branch off, then re-enforce the heck out of it in hopes that it doesn't break.

Here's how that turned out:

 

[rodney]

I have some trike plans if you pm with email.

 

[parajared]

There is something I don't catch.
I am not a frame builder, and I don't know much about trikes...
But my logic is hurt. Why would you want to weld a part that has a bearing in ?
IMO, bearings are inserted and components assembled after the frame is welded, polished, even painted.

yes the KMX is wierd. The bearing that is in the steering post is in a position that appears to be welded in. I don't see any way to service the bearing other than cracking out the cutting torch and chopping the steering mount off.

 

[JEB]

On the trike I built years ago I used BMX 48 spoke 20 inch wheels with 14mm axles, the axles were long enough to thread them to one end, (exposing almost 2" of axle) then I drilled out a piece of tube so that I could weld to the steering tubes, mounted them using the original hardware.

 

[docnjoj]

Here is how the Tricruiser is done. No welding, just a bolt through thick alloy. Sid Gowdy used to do ultralight aircraft before the trikes.View attachment Tricruiser front spinsle.doc

 

[chisixer6]

my early 1990's trike uses Sturmey archer drum brakes assembly and , axle is suspended on one end

http://compare.ebay.com/like/230962544023?var=lv&ltyp=AllFixedPriceItemTypes&var=sbar

 

[parajared]

update 1/8:
boring the guts out of a BMX wheel failed: I couldn't find a good way to cram a bearing in there. The OD was too small for a good beefy ID. Maybe plastic BMX rims that I could bore a bit larger would work.
Utahtrikes.com sells trike wheels for $120 a pop; this is a bit too spendy for a junk on wheels project IMO.
Bikesatwork.com sells the Skyway Tuffwheel for $43 per wheel. This sounds tempting, but I bet I could still do cheaper.
http://www.bikesatwork.com/store/product/skyway-tuffwheel-16

thanks to whoever sent the packrat workshop link. Interesting read, I am almost finished with my packrat style build with forks welded to the axle. I believe this is a pretty good way to go, because thrift store bikes are usually less than $15 and the brakes on the donor bike line up perfectly with the wheel, no additional fabrication needed. Will post pics once everything is done.