It's funny because I saw these axles (from BMI) being sold on eBay and people were bidding $27-$30, which is higher than if they simply went to their website and ordered it....

Then I TIG welded up both sides of the subframe, being careful to ensure that vertical tubing is as close to 90 degrees as possible. The beveled corners saved a lot of work so that I don't have to plug any open tubing ends when done, but make it a little tougher to get exact alignment.

This is where it really pays to have a flat welding table that you can clamp the parts into position so that the parts don't move as you are welding. Heat from welding causes a lot of pressure to 'pull' parts, tack weld all together and then re-check for alignment and squareness, if off once welded your only recourse is to take back apart and fix...

Completed welding up the engine subframe today, the design is slightly modified from the original plans as I allowed for a similar mounting at the front of the frame as is used in the back. My Vortex chassis was built with this in mind. Will add 2 small vertical supports to the side rails after I dummy up the engine into the frame, my thinking is that I might be able to use them as attachment points for stuff like shifter/clutch cables.

I will be using standard style rear axle adjusters, rather than have a fixed mounting point for the rear axle through the swing arm I made some 2" long slots so that I can easily fine tune the adjustment of the drive belt rather than using shims. I feel even though the use of the adjusters is another modification, it will make the alignment of the rear tire *far* easier than using shimming technique mentioned in the plans.

Right now I left additional material onto the ends of the swing arms and will trim back when finished. The plans also call for 2 horizontal tubing braces that go from the side rails to the front tube, after I assemble the rear axle and check for clearances I will add them.

Here are various shots of the swing arm assembly so that you can see better the orientation of all of the parts. When you weld this up be sure to have the shock spacer at the upper bracket bolted in place, if not there will be a pretty good chance not having the bolt holes align up as welding causes parts to pull and move slightly due to the heat! In fact when welding always have the base of the unit clamped down to your welding table as welding all of the other stuff onto it will warp the whole thing and your axle will not end up parallel with the front tube.

Important Note: If you vary from the original plans and use either thicker plywood or more layers of fiberglass mat, then you will need to ensure that the holes are spaced far enough from the corner of the angle iron so that the inside angle iron can receive the matching hole without interfering with putting a nut onto the bolts! Make a test bracket by drilling a piece of angle iron for proper hole placement with 1/8" drill bit, and do not weld on the top plate yet. Place this bracket at the approximate location on the chassis that it will go and drill a test hole into the chassis, put another piece of angle iron on the *inside* of the chassis and using a drill bit mark where the hole will be on the inside angle iron. Remove it and drill to full size, add bolt and nut, if you can get a wrench/socket onto the nut then you are good to go, otherwise you will have to possibly use larger angle iron on the outside and move the holes outward so that there is no interference on the inside angle iron backer.

Using a torque wrench I tightened the nuts until either the nut or the bolt broke.
Here are my results:

Now I understand that by putting in a bunch of 1/4" bolts that cumulatively they give you strength, but my butt literally is on the line here and I am uneasy about using them as they hold in the engine subframe and that holds the rear swing arm. When the tire either hits a bump or pothole all that energy is transferred to the chassis through these bolts. Paranoid me will be using 3/8" grade 8 bolts/nuts all around, also including the front subframe for the same reasons.

I estimate that I will be torqueing the 3/8" bolts & nuts between 40-50 ft/lbs.

So I decided to rework the brackets that I made last week, actually I will scrap what I made and start over. What I will end up with is on each bracket there will be 2 3/8" bolts on the horizontal and 2 (or 3) 3/8" bolts on the vertical surface (2 on the vertical surface would probably suffice...) The horizontal holes are staggered from the vertical holes and the bolts will have the head cut off and welded. 5/16" bolts would probably be fine here but as long as I am doing it I will error on the larger size.

Here is a quick drawing so that you can understand what I will end up with (drawing does not include top plate that bolts to the engine subframe so that I do not infringe on any copyrights, only the bracket is shown for clarity).

If you go this route, before you weld the studs into the angle iron, drill the chassis where these studs will go so that you get proper placement of the holes and drill the chassis. Next put the angle iron inside the chassis and mark/drill these holes as well. Next weld the studs in place in the bracket and flush grid them. After cooling you can can treat studs with lock-tight, assemble the bracket along with inside angle onto the vehicle insert washers/nuts and tighten. Finally drill the remaining 3 top holes and add the remaining bolts.

In addition a couple of people on the Vortex Yahoo discussion group have mentioned about using epoxy in the bolt holes that go into the chassis when you insert the bolts, the epoxy will harden and reinforce the hole. To be most effective you would have to drill the holes in the chassis slightly oversized so that the epoxy forms a tube around the bolt.

Completed the 2 mounting brackets that mount the swing arm to the engine subframe, but forgot to reference the plan sheet and incorrectly located the gussets, too close of course. I had forgotten and in my mind the the brackets were inverted, but the side with the gussets go towards the inside, not outside and there needs to be clearance for the front tube of the swing arm.

When I welded up the engine subframe I put in plugs that can take 1/2" bolts for holding these brackets on instead of 3/8" bolts. So the slots in the brackets will be made to accommodate the larger size, that is after I get the new gears into my mini-mill. Got the head all stripped down, I just have to find a local place that has a hydraulic press to remove gears from the quill shaft.

Recently I found this engine for sale @ VFRWorld website in their classified section. After researching these 90 degree V-4 style engines I was pretty impressed, and they are a bit more compact than the inline side to side 4 cylinder style engines. In 1998 they added fuel injection and also came out with an 800cc version and I believe that around 2001 they put out a 1000cc version of this engine.

As luck would have it the hookup for the speedometer is coupled to the drive sprocket on the engine and not the front-fork of the bike. There is a good chance that I can take advantage of this, might need to change the ratio - but it is a good start!

I will be driving to Kentucky to pick the engine up today.

It turns out that the guys that I got the motorcycle engine from, acquire wrecked motorcycles and they typically disassemble them and parts them out. They had a half-dozen motorcycles at the time that I stopped by of various makes and sizes. Check out my links page for contact information for Kentucky Cycles.

Here are the engine specs courtesy of VFRWorld:

Finished up the brackets for mounting the swing arm onto the engine subframe today, making sure that I allowed enough room to clear the round front tube of the swing arm. Below is picture of them.

Got the 1" intermediate shaft cut to length, and mounted the pillow blocks with the shaft in place. I will be needing to put about .025" of shim material behind the middle pillow block as it is next to impossible to get all 3 pillars perfectly aligned when welding.

I finished up 4 of the mounting brackets to mount the engine subframe, I was able to rework the old ones by cutting off a section and welding/flush grinding some extensions both on the top and the side. I redrilled the brackets to accommodate 2 3/8" bolts on the top and 2 3/8" studs on the sides. After locating all of the mounting holes on the chassis, I took the brackets and TIG welded the 3/8" studs into place using a quick fixture to help hold things in place, then flush ground the weld. Here is a shot of a couple of them. Since I am using 3/8" bolts I decided that 2 on top would suffice.

Next I cut the pieces of angle iron for the inside supports, numbered them and the brackets so that I would know which are pairs. Then holding the inside angle iron in place I used a 3/8" drill bit to mark where the inside holes go, then removed them and drilled them slightly oversized on the mini-mill. Put them back in the chassis and bolted to the fixed studs on the brackets. With brackets held tightly in place drill the remaining holes on top and bottom through the chassis and inside angle iron.

A slight problem became evident as 2 opposing corners of the subframe were hitting the mounting brackets, so removed them and took a grinder to the fiberglass area behind them so that they would provide more clearance. There was quite a bit of glass around these corners due to all of the overlapping layers of glass from both directions. After some judicious grinding the brackets were replaced and the engine subframe slid in with about 1/32" of clearance...

I guess the moral of the story is to ensure that when you build the engine subframe be sure to allow for a bit more clearance. In measuring I think that I tried to allow for a total of 3/8", which would make each side have 3/16" clearance. Taking into mind that the brackets are made from 1/8" material that only left 1/16" on each side. Due to slight variances from the glassing operation you probably should shoot for 1/2" total clearance. Be aware that this dimension affects the width of the front tube of the swing arm - and any variation from the plan sets for the width of the engine subframe also need to be carried into the swing arm!!!

This is not a problem as I will make a wood spacer slightly wider than the desired inside dimension, and insert it before I weld in the 2 side braces. This way when the swing arm cools it will be slightly wider than needed in the back, making installation of the rear axle easier.

The ones that I got were originally meant for a trailer but I will either splice them together or split one and fabricate a 'filler strip' to make it the desired width. I had also seen some fiberglass fenders on eBay but opted for the steel ones. If you are not able to weld steel then the fiberglass ones might be a good compromise.

By having both of them I can use the one that orients itself better since each of them turn in the opposite direction. They are 24v units and I will either run them off a single 12v battery or add a second 12v battery if necessary, will have to see how they work on 12v first.

Here is a picture of them:

Last night I did some quick calculations pertaining to reverse gearing and this is what I came up with:

Rear pulleys for the Vortex are between 64-71 teeth, the pulley on the intermediate shaft is between 31-34 teeth. This means that the intermediate shaft will rotate approximately 2:1 with the rear tire.

It would seem appropriate that a reasonable reverse speed would be about 2 ft/second. With the circumference of the rear tire being about 75" (24" diameter x PI) then the rear tire would have to turn about 1 rotation every 3 seconds. Translating that back to the intermediate shaft then would have to turn about 2 times every 3 seconds or 40rpm.

With a gear motor for a wheelchair that has a full load rpm of about 145rpm, you would therefore have to reduce it using a 3:1 pulley to the intermediate shaft. This would give you the desired maximum speed, if you used a pulsed width modulated (PWM) controller you could efficiently control the speed, from very slow up to the max speed allowed by the motor.

Also fabricated the rear shock brackets, drilled them and welded onto the engine subframe this weekend. I bolted the brackets onto the shock to ensure correct spacing and to maintain hole alignment while welding. It turns out that the shock is 7/8" wide and not 3/4" wide so will have to make another aluminum spacer for the shock mount on the rear swing arm.

Once all brackets were installed for the engine subframe, I located where the mounting holes were on the subframe, drilled, plugged, welded and ground all flush. There really is a *lot* of work that goes into the engine subframe, there is a lot of detail work (namely the 14 plugs) that are necessary so that the tubing does not crush.