99cc rack mount 3 speed spoke drive MTB

Where to begin? This odd build is directly inspired by the groundbreaking work cannonball 2 has done with his current Maytag build...

http://motorbicycling.com/showthread.php?t=57197&page=19

...the link takes you to a midpoint in his thread where at post 187 he decides to give his under powered Maytag some help with gears by utilizing an old salvaged 3 speed internally geared hub as found on skinny wheel bikes from the 1960's and 70's. He is choosing to use the hub itself as a friction drive roller in direct contact with the bike's rear wheel and taking advantage of the hub's three gears. Cool beans! What was already a very interesting build just got a lot more interesting!

Road testing proved the concept worked, but the Shimano hub was not up to the task and failed. Further testing with a more robust salvaged Sturmey Archer 3 speed hub did not fail and is still running strong.

http://motorbicycling.com/showthread.php?t=57197&page=24

This link will take you to the next important flash of brilliance at post 238 where he attempts to improve the engagement between hub roller and tire by threading old spokes from side to side through the hub spoke holes. It has worked out very well and appears to have eliminated the big limitation of friction drive... slippage in wet conditions. Without eating the tires the spokes press down into the tread and really grip the tire. Awesome! And so far this is from used stuff!

Cannonball 2 is an innovative builder who knows a lot and is willing to try new things. He's still doing it with other aspects of his Maytag build which is ongoing (check it out), but for my purposes here in giving you some background with what I'm up to and by having my own thread I will stop highjacking his with too many excited questions. I want to emulate his spoke drive 3 speed hub and share with you the adventure.

Ben has done a number of friction drive builds in the past and I have learned from his work and in turn from those he learned a few tricks from. It has been said that "we stand on the shoulders of those who came before us" and it is true, I think. I wanted to give credit where credit is due.

So, what I have in mind is a very simple, low cost build using for the most part what is already at hand. The idea is for an easy to ride, low maintenance trail bike also comfortable for cruising. A more comfortable seat and cruiser handlebars will better suit an old fellow. A kiddie trailer for Aaniimoosh The Wonder Dog will follow.

Pictured below is the mountain bike I found at the dump earlier in the winter. Brought it home, put air in the tires and found there was nothing wrong with it. It isn't a high dollar bike, but has a suspension fork, good brakes and the price was right.
(cont.)
SB

The first photo below shows you the business end of a mount for a sidemount friction drive unit from an old moped I found. I saw the possibilities for using this part of the mount for a behind the seat rack mount and have attached it to the MTB. It is designed to have a hinged portion riding over the wheel which I will make from two parallel pieces of bed-rail angle iron. The four stroke engine will bolt on to the two rails and by being hinged can tilt up or down.

http://motorbicycling.com/showthread.php?t=31318

This link takes you to another of CB2's friction drive builds where he uses a scissors jack to raise and lower the engine (4th photo on post #1). He gives credit to Deacon for this idea and I will pass the credit along accordingly. With a simple squeeze of a brake lever at the handlebar the engine raises up or down, in effect acting as a clutch to engage the roller to the tire. Brilliant! In the case of the photo the engine is mounted to the side so the crankshaft itself is the roller. We aren't going to do that since we want the benefit of gears and spoke drive. And I would like for the weight of the engine to be closer to center over the wheel.

So, we will have two angle iron rails which the 99cc Predator four stroke is bolted to and the forward end of the rails are hinged to the mount bolted to the frame. At the other end of the rails there will be an axle slot on each one, something like dropouts on a bike frame where the wheel would go. We aren't bolting a wheel on, but we are attaching the 3 speed hub at a point on the rails where in the lowered position the spoke drive engages with the tire. Raise the engine and the spoke drive raises with it. How's that for simple?

Like Ben, I will change the hub's drive sprocket to a pulley as I think it will be easier on the internal gears. I had initially thought that I would need a jackshaft with two pulleys, one receiving the belt driven by the engine crankshaft and the other pulley driving the belt to the geared hub, but it may be that the jackshaft can be eliminated. Still thinking about that.

Also pictured below is the 3 speed Sturmey Archer hub I intend to use. Most of these were free wheeling types while this one used a coaster brake. The brake arm will be removed and the hub flipped so that the sprocket (soon to be a pulley) will be on the left side of the bike the same as the drive pulley at the engine.
SB

Point well taken. I have a question for you. I'll know better after I have removed the 99 Predator from the other bike and have made up the rails to support the engine and drive hub, but I may be able to do this without the jack shaft. If I can manage this with just a pulley at the engine and pulley at the hub what sized pulleys would you guess would maybe work, understanding that a pulley size might well need to be changed later to tweak things. But as a starting point, what would you guess?
SB

http://www.amazon.com/Schwinn-MTB-T...8&sr=1-2&keywords=24+inch+mountain+bike+tires

I was considering this one. After the sun is up I'll take a photo of the tire tread on the bike now to see what you think. Would the front and rear necessarily need to match?

http://www.amazon.com/Duro-Knobby-T...492881&sr=1-62&keywords=24+mountain+bike+tire

The second tire is twice the price but probably has the better tread pattern to match the dig of the spoke drive. Other than the pricing and being 24" it is the same tire you purchased, I believe. If I only buy one tire for the drive wheel it would keep the expense down. This is through amazon and I do have prime so the shipping is free. I could check with your ebay seller to see if he has the deal you got in 24".

With the scissors jack would I still need an automatic clutch? Or would the scissors jack engaging a running motor at idle with the wheel eat the tire?

I won't know until I have the motor on the rails how the pulleys might align, but the engine could be offset a bit and for that matter the hub is wide enough that it, too, could be offset a little. The engine would not end up centered exactly above the wheel, but pretty much so and would be a lot better balance than a side mount using the crankshaft as the roller. One reason I was hoping to bypass the need for the auto clutch is that the drive pulley could ride very close to the engine. The auto clutch would set it out an additional inch+ from the engine. Every inch counts.

The automatic clutch I have has a pulley measuring 3 1/2" at the outer edge. At the base of the belt it would be about 2 1/2". I'll post a photo later in the day. For the geared hub I can get the weldable pulley with 1 5/8" core in 4", 5", 6" or larger diameters.

Your thoughts on all this are much appreciated. Gear ratios make my eyes spin around in dizzy confusion. Not a pretty sight.

This bike is going to fun, I think.
SB

Curt,
The set screws are only accessible with the pulley & bell housing removed.

HOWEVER, I could skip locking it down with the clutch set screws and lock it in place with a lock collar, right? That would work. That way the pulley could hug the engine, like you said.
SB

Here's a good deal on tires and tubes, but maybe the tread isn't quite right.

http://www.ebay.com/itm/2-24x1-95-M...6&pid=100005&rk=3&rkt=6&sd=181483931624&rt=nc

Pictured below is the 1950 Schwinn Panther which is getting an engine upgrade from the 99 predator to a 147cc Jacobsen. Qmatic tranny will stay with the bike. Predator engine will get pulled this week for the MTB spoke drive.

Also pictured is the clutch salvaged from an old snow blower and which Curtis adapted to pulley from sprocket. If I remember right the clutch was set to engage at pretty low RPM so should be suitable for the Predator.

And finally there is a picture of the tread on the MTB wheel. It is 24X1.85 Can I use a wider tire to replace it? Or is it a suitable tire to use as is?
SB

Looks to me like the best options are the Innova...

http://www.ebay.com/itm/271414822276?_trksid=p2060353.m1438.l2649&ssPageName=STRK:MEBIDX:IT

...and the Duro beach cruisers...

http://www.ebay.com/itm/131122337617?_trksid=p2060353.m1438.l2649&ssPageName=STRK:MEBIDX:IT

with similar pricing within my budget. Truth be told I would probably not spend all that much time on rough logging roads, riding most on well paved road, so the Innova might be suitable. They are also closer in width to what is on the bike right now at 1.95, while the Duros are 2.35. I don't know that the width would matter much. I had figured to run all 18 spokes, but am open to using whatever works. Assuming they cost the same and thinking in terms of tread alone, which pair do you think would be best? I doubt that the ride would be all that different since the tread on the Innova might be a bit smoother, but the Duros being wider might be as comfortable. The tread also looks a little deeper on the Duros. Decisions, decisions...
I would order a set at the beginning of the month.
SB

Intrepid Wheelwoman said:

I like the look of those Innova tyres, I've run a similar tread pattern on my tricycles from time to time. But those beach cruiser tyres really made me sit up and look as I've never seen a tread pattern like that before.

Nice to see pictures of one or two of your bikes being woken up after the long Winter Silverbear

Click to expand...

Thanks for your input, Anne. If you were me (be glad you're not) which set would you order and why?
SB

Intrepid Wheelwoman said:

What I like about the Innova tread pattern Silverbear is that it's a good all rounder. I don't exactly do any dirt road type riding, but living in a rural town means that road surfaces can be variable and in the wet season mud and water happens a lot.
I've tried more knobbly tread patterns before and on my tricycles at least the tyres seemed to wear out very quickly due to less rubber actually being in contact with the road. Mind you I tend to use my tricycles like a pick up tuck so they do carry some heavy loads which could be a factor too.

The Duros are a nice looking tyre and I'd most probably consider them if I was riding on loose surfaces more often, but overall my vote goes with the Innova tyres.

Click to expand...

Thank you for your considered opinion. I'll be interested to hear Ben's choice. I don't picture aggressive riding or shifting quickly, trying to do a wheelie... that sort of thing. I mostly want something fairly comfortable and that will allow the spokes to grip the tire well.

I also wonder if there would be a difference in gearing due to the difference in tread pattern. The Innova appear to be closer together and the Duro deeper and further apart.
SB

Having given it a lot of thought, I'm leaning toward the Innova tire set. One consideration is that the width of these is 1.95 and the tires on the wheels now are 1.85, generally of the same size, while the Duro set is a good bit wider at 2.35. Curt has a set of the Innova and reports that they have worn well for six years. As Anne pointed out the tread pattern is such that there's a lot of road contact compared to the fewer nobs on the Duro's. And I suspect that the Innova tires will give a smoother ride.

The clutch pulley is slightly less than 3 1/2" at the outer edge so I think the intitial try at a pulley on the drive hub will be 7". If it proves in use to need either a larger or smaller pulley then that will be simple enough to change as I have more than one sprocket to modify. I had initially thought to do away with the automatic clutch, but have decided that it will make for smoother operation and perhaps less wear at the tire if the hub is already against the tire when throttled up. So it will have both an automatic clutch and the scissors jack to raise and lower the engine and drive hub for complete disengagement from the tire. No jack shaft.

Fresh snowfall has made outdoor bike work more difficult, but as soon as warmer weather returns within a week I intend to pull the predator engine and make up the engine mounting rails. Tires will be ordered at the beginning of the month and hopefully the build will come together quickly.

I expect to change the seat and the handlebars for greater comfort, making the MTB feel more like a cruiser.

Nothing is set in stone at this point, so if there are any suggestions I welcome them.
SB

Thank you for your thoughts on this. It sounds like the spacing of the nubs on the Innova tires is just right for the engagement of the spokes. Do you think that the greater depth of the Duro tires make them a better choice? Longevity of the tires is not an issue. How well they work in this application is the concern.

If I use a scissors jack would it being spring loaded along with the weight of the engine and hub be enough tension against the tire to keep the spokes from riding over the nubs?
I suppose it would depend on the strength of the spring. Perhaps a different lever system would give more tension than even a stiff spring. I have a mechanism from a Bikebug engine that is for engaging/disengaging the drive roller which might be made to work for this application. Or a very stiff spring arrangement along with a gated lever rather than a hand squeezed brake lever might work as well. I have such a mechanism that was some sort of gear shift from who knows what... part of my junk treasures. I'll take pictures of both for creative staring. I can see the need you point out for the spokes to firmly engage the tire.
SB