Grubee, Nuvinci Frame Mount Build


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2:53 PM
Jun 14, 2008
Las Cruces, NM
My latest MB project was adding my Grubee 4-stroke kit to a Cadillac Fleetwood bike that comes with a Nuvinci hub. I fabricated a jackshaft to bring the chain to the right side of the hub. Most of the parts for the build were purchased from Staton.

Some photos of the MB

Here are the parts I used for the hub:
27-tooth sprocket for drive chain on hub
16-tooth freewheel for pedal chain
Washer to space between the 2 sprockets on hub
Torsion bars to keep hub from twisting in drop outs

Here are the jackshaft parts:
9-tooth keyed 410H sprocket
18-tooth keyed 410H sprocket
5/8 inch full key way shaft (6 inches)
5/8 inch shaft collar (qty:2)
3/16 x 3/16 x 1/2 key (qty:2)
2-bolt 5/8 flanged bearing (qty:2)

Here are the miscellaneous parts:
1-1/4 inch stainless steel saddle clamps (qty:2, note that I had to order 3 to make minimum order amount)
Drive chains (qty:2)
Throttle grip to replace Grubee dual brake controller and throttle
4 inch x 1/8 inch square steel tubing (6 inch length)

I also had to order the 2 piece Nuvinci hub dissembly/reassembly tools from a local bicycle store. Contact Fallbrook Industries (Nuvinci manufacturer) customer service to obtain a Nuvinci Owner's and Dealers Manual or obtain online. The Dealers Manual has the part numbers for the tools, but only listed one of the tool's part numbers. You will need both tools, which in my case were packaged together. Fallbrook can also tell you the tool wholesaler. I paid approx. $80 for the tools. The tools allow the installation of the sprockets on the Nuvinci hub.

After I drilled the holes in the square tubing for the jackshaft, bearing bolts, and u-bolt clamp bolts I cut one side off of the square tubing to make it a u-bracket. I also bought some stainless bolts and square aluminum tubing to secure the flanged bearing and to keep the u-bracket from spreading or collapsing.

I used a soldering iron to remove the sleeve from the throttle cable in order to attach the Grubee throttle cable to the new throttle grip. Be careful not to cut it too short. I cut a little at a time and experimented. Once I had the right length, I soldered the collar back on the end of the cable and reattached it to the Huasheng carburetor.

The bike will go 26 miles per hour on the flats, but the gear ratio is not quite low enough. I am able to climb a pretty steep hill at 15-16 miles per hour without pedaling. I weigh 265 pounds. The engine is not running in its power band at the highest 'gear' of the hub, so I plan on lowering the gear ratio to give better performance and possibly speed (given my weight).

If your Grubee gearbox did not come with lock and flat washers, try to get them from or a home supply store and use Locktite as the gearbox mounting bolts can come loose and cause the clutch drum gears to strip. This happened to me and I had to order replacement parts from Give Jeremy a call at He is very helpful.
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more info

Here are more parts I used.

Bottom bracket parts:
I found a longer bottom bracket spindle at a local bike shop that specializes in mountain bikes. The original spindle length for the Cadillac Fleetwood is 123 mm. I needed a spindle at least 5 mm longer on the left side (133 mm spindle) to allow clearing the exhaust pipe. I mounted the engine and jackshaft high enough to allow the pedals to clear them. The bike shop was kind enough to let me use their tools to remove and reinstall the bottom bracket. Note: do not over tighten the bottom bearings.

Torsion bar parts:
U-joint retainers (qty:4) for attaching the dropout frame to the torsion bars
Allen head bolts (came with u-joint retainers), lock and flat washers, and nuts from hardware bins in Lowes for mounting torsion bars to frame

I bent the torsion bars to allow clearance where the frame attaches to the dropouts and then bolted them to the frame members using the u-joint retainers and bolts. Tighten the drive and pedal chains before tightening up the torsion bar mounting bolts and retainers. I used the horizontal torsion bars from Staton.

Gas tank mounting parts:
Exhaust clamps for attaching gas tank (top frame tube is too wide for tank mounts)
1 in. x 4 in. flat steel (qty:2) from Lowes for gas tank brackets (drilled 2 holes gas tank bolts and 2 for the exhaust clamp in each plate)

Jackshaft to motor mount bracket parts:
1 in. x approx. 7 in. x 1/8 in. flat steel from Lowes for bottom plate
3 in. x approx. 6 in. x 1/8 in. scrap steel (from square tubing)
stainless steel sleeves from the hardware bins in Lowes for spacers between gas tank and flat stock

Here is how I made the jackshaft to motor mount bracket.

Bottom plate: I bent the 1 in. flat stock to wrap around the motor mount and bolted it using a long bolt that mounted to a hole I drilled through the motor mount. I positioned the bottom bracket before marking and drilling the motor mount.

Top plate: I cut the scrap steel from the square tubing to make the 3 in. x 6 in. and drilled holes to attach it to the bottom u-bolt attaching the jackshaft to the seat post with the top plate resting on the bottom plate previously bolted to the motor mount. I removed the bottom u-bolt leaving the saddle in place a marked the hole using a short scribe to mark the holes to drill.

Bolt the bottom plate in place. With the jackshaft bolted to the seat post and the engine to jackshaft chain tensioned, bolt the top plate to the jackshaft u-bolt so it rests on the bottom plate. Take the bottom u-bolt out to mark the spots to drill for mounting to the jackshaft. Weld the top plate to the bottom plate while mounted to the bike. Remove the bracket and chip and grind the weld before wire wheeling, priming, and painting the bracket. Remove the bottom u-bolt from the jackshaft leaving the top one tight to allow installing the motor mount to jackshaft bracket.

I was able to mount the chain guard from the Grubee Skyhawk II kit to the jackshaft and torsion bar mount after trimming the chain guard with sheet metal shears and drilling out the mounting holes. I also had to trim some of metal from the factory chain guard for the drive chain to clear.

I also forgot to mention in the last post that I cut a rectangle out of the jackshaft bracket with a fine tooth jig saw to allow the chain to connect the engine and jackshaft. I also used a vise and a small grinder to smooth all the edges on the jackshaft brackets.
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