3 speed Sturmey Archer hub as a jackshaft

[professor]

I have been using one on bike #1 for a couple of years and love it.
That bike has a HF79 greyhound for power. It is geared to top out at just over 30 mph.

I decided to put one on bike #2 which has a HF212 black motor.

This bike has full suspension with moped wheels, front end and seat.
Rides like a dream. The engine has enough torque to easily get going ( idle speed is 10 mph in gear) but the vibration and engine noise / buisyness gets to me, so I want gears to flatten the rpm.

Note- these big engines vibrate BAD, real BAD, so mine is mounted with rubber isolators (6 of them).
If you are thinking about doing a 4 stroke, I recommend staying down below 100 ccs. The difference is unbelievable.}

I found some wheels on Craiglist that had a hub, so I cut the spokes and started adapting the hub. On both bikes a primary jackshaft is needed to send the power to the right side of the bike.

Hardest part is welding the pulley/ sprocket on.
I am using belt to the hub - so I welded a pulley to the existing sprocket by cutting out the hub portion of the pulley (steel stamped type) & centering it by locking the hub axle in a vise and clamping the pulley to the sprocket ( there is just enough room for little C clamps)
Spinning the hub and tapping it centered until it spins true. Note- this is real tedious, it has to be as true as possible. Tack two spots -remove clamps and test spin it, if it spins without noticable run-out- weld it to the sprocket.

Note- the welding ground must go to the pulley NOT in any way thru the hub bearings and gears! I even put wood between the vise jaws as a safety against arcing where I don't want.

Welding on a sprocket to the hub body on the other side is harder.

I used a freewheel that I took apart (they come apart by whacking the little ring with holes counter clockwise with a punch. While holding the knotched backside with a tire-iron clamped in a vise).
The freewheel is harder because there in no way to hold it in place other than with fingers after it spins centered.
The welding ground clamp can be attached to a visegrip locked to the ridge where the spokes went on the hub. Again- juice must not go thru the axle as it is clamped in the vise.
Tack and check for out of round, if Ok do little spot welds around the sprocket, taking time to cool.

The oil fitting on the hub must be leak proof. I shoot some oil in the hub every couple months
The axle in the hub has anti-rotation flats- make some provision for that, I welded around the plates the hub mounts to fit the flats.

Will add some pics tomorrow (can't get this computer to do it).

 

[Racie35]

Neat but.....my 212 doesn't vibrate.....have you changed any of the rotating parts?

 

[professor]

Well that is good news. I am glad yours is OK.
No, the engine is totally stock internally. One of the first ones they made.
I even bought a clone go kart motor to try, and it was as bad as the HF.

 

[Sidewinder Jerry]

Good close up pictures. How about some showing the set up on the bike? How well is it shifting?

 

[professor]

OK, (it took me a long time to figure out how to get the pics onto here earlier today), bike looks a little weird, but rides and handles great.
As for shifting, I have a trigger shifter on order from Niagara Cycle but have shifted the bike with a thumb shifter until it comes. Like I say bike one has one and it works flawlessly.
Oh and the freewheel aspect of the hub is nice. You still can pedal but with effort. Bike weighs 140# ( two more than me). To shift up or down you let off the throttle -

 

[professor]

Update

Ordered different primary pulleys to up the groundspeed (also, there is less clutch slip with the larger engine pulley having more area engaged to the belt.

Overall gearing is 10.5 in first, 7.6 in second and 5.7 in 3rd. Seems perfect, put-puts calmly at my normal 20-25 mph. Nice acceleration, clutch slips a little but it is OK- less load on the 3 speed hub, I guess about 6 hp is transmitted.
Just ordered a trigger shift from Niagara cycle, all is good.

 

[Lee_K]

There's lots of ways to adapt sturmey hubs to MB's. You came up with a straight forward way of attaching a pulley & sprocket and I like the way you managed to fit all the parts in there. None of that's easy, but you got nice results.

So with a 7.6 overall ratio you must only be running around 2000 rpm at 20 mph, with that big muffler and low rpm's it must be quiet.

 

[professor]

Actually, the final is 5 something. Second gear is 7.6. But I think you are right about 20mph being a fast idle.
I just went downstairs to look at the moped muffler. Yikes- I forgot to drill out the endcap! All this time the engine was exhaling thru a tiny stock 50cc opening. No wonder it was so quiet.
Did some drilling, added a mid muff that I had made and went for a ride.
The hub transformed the bike.
Reminds me of a Honda 175 I had, only I think the 212 pulls harder past first gear (first slips a little). No intention of testing top speed.
A mini motorcycle with pedals.

Trigger shift came yesterday and it is on.
The primary pulleys are changed too.