Hi Rick,
I know you post over on the motorcycling forum, and this is probably what you wanted to post here:
Hi & thanks for following, I've read many of your posts and your Pope is righteous! Very cleaver details & just looks right. Went over to Custom M.B. sight & that's 75% of a co-axle drive & the price is right. 3/4" shaft & bearing races for 2" American press fit bracket shell good stuff. If you don't have your own machine shop you will pay at least double what CMB is charging.
I'd also consider calling Pat at Sportsman Flyer, as he has the sprockets as well as the above in a reasonably priced package, set up for his builds...probably need some minor custom machine work on the sprocket carriers for your application... to get correct chain spacing for your setup.
If however you choose to build your own. Here's what I needed in addition to what CMB is offering. 2" steel American bracket shell, cut it off an old frame or search the vendors. Get the axle parts first & make sure the measurements are correct for the exact shell I.D. & length. You can also have a competent machine shop turn a steel shell to s I turned my own parts. I then squared up another 2" inside diameter tube & milled a saddle using a side cutter. This cradles the bracket shell for welding. you end up with a T shape which I welded to a quarter inch steel base plate which was in turn welded to the two frame rails. You are probably building on a single tube frame, if that's the case the shell is either already welded in or you would add it in a somewhat typical bottom bracket location. Build a motor mount cradle & attach to frame weld tabs &/or clamps. I used the Harley clamps and they are wicked strong but pricey. I also used 2 weld tabs for one of my rear engine mounts. These were welded onto my bottom bracket tube.
Main thing on the bottom bracket is to get the axle level & the axle ends parallel with the bikes center-line or the sprockets will wobble.
My engine is set up to be adjustable to left or right, but my goal was to do it once, but make it easy to pull the motor for service. The motor was positioned for balance & then locked into the mounts. I chose to eliminate front to rear adjustments as I chose to not have an adjustable bottom bracket. Both the pedal side chain as well as the secondary chain to the back axle are adjustable only by changing chain length, axle position and the secondary chain by idler sprocket tension. Primary chain is adjusted by length of chain & roller idler tension.
The two sprockets are jack shaft 3/4" identical size. With rear tire mounted with final drive sprocket I established a straight chain line with the inside co-axle sprocket & located a shaft collar to maintain that spacing which was both straight and prevented the chain from ever drifting into the rear tire. I had to actually mill the collar to about 2/3 rd. of it's original thickness to keep the chain at least 1/4" off the tire.
With the engine output sprocket parallel to the bikes true center line a measurement is made to establish the distance between the two free wheeling co-axle motor drive sprockets. Distance between motor drive sprocket & the previously spaced inside co-axle sprocket is made & that distance is the total width of the two jack shaft sprockets when they are welded together. If that distance were 4.5" (measured to center of each chain line) & the combined width of the two jack shaft sprockets is 5" then 1/2" of thickness would need to be milled or surfaced off. If the distance was less, then a plate of sufficient thickness would be added. The jack shafts will be eventually welded together, but the two sprockets must remain parallel to one another in order to run true. I use a 3/4" motor shaft cut off an old electric motor to perfectly align the two sprockets together for welding, prior to welding bevel the pieces for good penetration. After welding remove the alignment shaft & ream the 3/4" hole to accept two appropriate sized press fit bearings , flush mount on each side. I also drilled the remainder of the 3/4" hole 1/32" oversize. These steel jack shafts have a key way broached into them and a set screw is used to hold the key in place. Since the key way is useless in this application I use the set screw hole as a lube point & the over sizing of the 3/4" shaft hole allows the lubricant to flow a bit easier. Zert fitting will work in the same set screw location as well. The bearings are just lightly press fitted.
Another lock collar is placed just out board of the two co-joined free wheeling sprocket carriers & locked in place. If attention is paid to detail then all chain lines will be straight and the primary & secondary chains running parallel.
This seemed a quick and effective way for me. It probably took more time to write this post than it did to make the co-axle sprocket carrier, though the bottom bracket and axle itself took quite a lot more time. I could have milled sprocket carriers and bearing carriers out of aluminum or steel and just bolted sprockets to it & made it easier to experiment with sprocket swap outs, but with a 5 speed just didn't think I'd need to. Hope this helps for your Merkel. Rick C.
Great build Rick C!
