Recumbent trike component fabrication

The plans called for using a lot of salvaged components from other bikes.  I don’t have any frames to cut apart and wanted to use modern components for the most part.

The first pieces built up were the wheels. This was my first experience building bike wheels. These are built from BMX components and I even found 100psi capable tires for the nominal 20″ (604mm) rims.  Until starting this, I did not know there are 6 different nominal 20″ sizing systems  which are incompatible!

I needed 3 headstock bearings, one for each front wheel and one for the the underseat handlebars. For these I am using FSA “The Pig” . The bearings must be pressed into the headstock tube. Normally the tube is reamed with special reamer which I don’t have. Instead, I faced and then bored the shells on the lathe. These are 2.5″ long for the wheels. The bearing seats will then be press fit in place. The arms that go from the spine of the frame to the front wheels need to be coped to fit these shells.  Rather than cutting each to length and then coping the end I cut the pieces to double length and then used a 1.5″ hole saw in the middle. The tube is 1.5″ square so the hole saw nearly cuts through the sides.  This makes a nice clean arc faster and more accurately than trying to saw and grind per the plans.  You do need to clamp securely and do this in the drill press or mill. Use the lowest speed available and lots of lubricant.  The Bridgeport works nicely for this and I was using mist cooling as well to avoid damaging the hole saw .

You can see the nice fit-up of the coped arm ends against the bearing tubes.

The front axle shafts and steerer tube are also coped and shown at the approx 15 degree angle that is required. Steerer tube is 1-1/8″.

Crank bottom bracket is adjustable. The clamp bars were made the same way out of 3/16″ x1.5″ steel flat stock. The shell is a standard 74mm ISO threaded bottom shell from Framebuilder supply.  Here you can see the bottom bracket shell fit up and ready for welding. Note there is a shim on one side to allow for the paint thickness later. 3/8″ bolts secure it to the spine tube.

.Parts list for the front wheels. These were purchased from Niagara Cycle.


Recumbent trike axles

The front axles of the trike are some of the highest stress load components. I am using 20 mm BMX hubs but now need axles to match. The AZ (Atomic Zombie) plans call for taking bolts, welding on some material and then grinding to “fit”. I wanted to to do better. The axles start out as 7/8″ cold rolled steel. Then there is some metal lathe work to get them to finished proportions.

Raw stock should be 158 mm long. Face off the ends to 155 mm and center drill each end.

Mount in 4 jaw chuck and center it up.  Note that a 5C collet would not hold the stub end tight enough, and my dog and faceplates would not work for this size stock, so I had back to the chuck. Tail end center is a ~1/2 face solid center  to allow for the tool clearance.

Step down to 20mm for 133mm from the tail end. Test fit the hub. It should be a tight sliding fit. File if necessary.

Step down to .73″ diameter for 27mm from the tail end to prepare for threading  (sorry for the mixed units) .

Make a small 3mm wide by 2mm deep groove next to the step to allow the threading tool to run out into it.

Thread the end to 10 TPI and test fit against the nuts. I am using a double jam nut setup.

Drill through at 3/8 ” from both ends and for the length of a 1/2″ drill from the post end. 

Recumbent Trike Project

For me, life is not complete without projects. I need to build things or at least rebuild them. Merely using things, does not satisfy me for long. I have to “make it better”.  So this has lead to the current project, which is  a tadpole style recumbent trike (human powered – the VTX is not being harmed in the process).

The trike is base on the Atomic Zombie Warrior:    > It will of course have multiple modifications along the way to improve the design and make use of the machine tools I have rather than getting by with hand tools. Plus I am keen to add fixturing for stability and accuracy rather than hand holding or using props like buckets.

This is largely a welding project. So the patio we added last year outside of my shop is getting some use.   Many of the parts were purchased from someone who was parting out a cracked Trek carbon fiber mountain bike.

You start by building the rear fork and “spine” of the trike. The tubing is 1.5″ across with 1/16″ wall thickness.   The plans state the heights of the pieces, but omit the angles. The angles are cut and filed “to fit”.

The rear fork is the first assembly. The tubes are cut and then welded up. Tube ends are capped off with welded on pieces. The drop outs are added next. 

Her is a close up of the rear drop outs. You can still see the scribe marks for where I drilled and milled the slots.

This is the first test with the donor cycle wheel. It is nicely centered.

Here I am starting to weld up the spine of the trike. The blocks are ordinary melamine coated 1/2 ” MDF scraps that have been squared and notched for the tubing at the correct heights. The reference for this setup is the front edge of the board resting on the welding table.

Now with the spine welded up, it is time to fit the rear fork. So this means another trip back into the shop.

The front wheels are made from 20″ BMX components with a 20mm center shaft hub to handle the force of only being supported at one end. This is the first time I have laced a bike wheel. One wheel is assembled and ready for truing and the other is still awaiting assembly. However, the hub must be used for fitting the axles which will be turned on the lathe.