Insane 7 speed friction roller drive with common engines (tanaka, pocketbike, etc)

This is branching off of another thread about home-made wooden rollers for friction drive Dax/staton and home-made kits.

I have not built one of these but I expect one could be made very easily from an existing Dax/Staton friction kit, by adding extension straps/brackets to the channel, to move it farther from the seat tube, and cutting the stock quick-release straps shorter as needed. The new "drive roller" will be mounted between the straps like a conventional hub mounts in dropouts. The axle could even be mounted between simple drilled holes There is a method to my madness, read ahead!

Today, 06:04 PM

happycheapskate
Motorized Bicycle Elite Member

Join Date: Nov 2009
Location: Far Worse TX
Posts: 764
Re: Cheap and Easy Drive Roller
I have a design to beat all for friction drive lovers. Starting a new thread for anyone who wants to build one and report back!

This will probably sound crazy but I expect it would work very well, and eliminate a lot of guess work, and OWN all the hills.

5-9 speed derailleur shifted roller drive with " 1 inch " roller, any grit you want.

Imagine a Dax type engine channel, but about 2x as long, with the drive roller about the center, or closer to the bike seat tube. The motor will be at the end, and angled so it is about 1 inch to 1 foot above the wheel centerline. This will much lower the center of gravity and make parking easier.

Now the dax type engine and shaft will drive a fixed, toothed cog, which pulls a chain going around a 7 speed generic bicycle hub with 7 speed (or 8 or 9, yes, 9 speed freewheels exist! ) freewheel , and using the non-laced hub as a drive roller! (epoxy and sand, or other surfacing will provide the friction for propulsion). Now with an 11-23, 12-26, or even 14-34 tooth (common sizes) freewheel, you could have a HUGE speed range including both massive underdrive and as much overdrive as your engine can handle!

For the drive channel, instead of very expensive extrusion, I would suggest welding a lighter thickness of steel plates (3 long pieces for example) together to make the "U", and bracing the sides together with long bolts and tubular spacers (like the engines sit on for clutch spacing). This should be very strong and not too heavy, esp since any flex will be taken up by the chain, and shorter "straps" for the QR skewer side will equate more strength/flex resistance. Let me know what you think in my new thread here:



Quote:
Originally Posted by cannonball2
That is a point to ponder, how to shift it with out getting extreme on the engineering. Maybe a slotted engine mount with a heavy spring to hold it in "hi". A shift lever to pull it down to "low". Probably mounted to the top tube with a gate. Once you get rolling good shift to hi and the spring pulls the engine/hi roller over to engage the tire. You would still need the lift clutch to do so. UNLESS the roller is a cone, which is a vari drive and would shift with out having to lift it. A shifter with a good friction lock would offer infinate positions.

Re: Insane 7 speed friction roller drive with common engines (tanaka, pocketbike, etc

The only design problems, or "cons" I can think of so far:

1. Weight. This design will add some weight over that of a staton-drive, but not much, maybe a few pounds. Answer: mfgr. your own channel by welding sections of a lighter material and bracing them or just ignore the weight bc. you have gears.

2. Bearing burnout. The rear roller will be a conventional bicycle freewheel hub, with added friction material epoxied for traction. This part will be required to rotate 20 to 30 times faster than the tire equipped bicycle wheel. Answer: use a higher quality hub, and hi-temperature automotive/aerospace grease, and do regular maintenance on the hub. If the hub wears out, it is only $15-50 for a new hub.

3. Derailleur failure. If the "rear derailleur" that is used to shift the gears fails, shifts over the limits past the cogs, bends, or it's pulleys burnout, it could shatter the chain or derailleur in close proximity to the rider's arm or butt , and of course, the bike will not be able to continue under power. Also these apply if the chain jumps the driven cog at the motor shaft. Answer: use a durable rear derailleur and decent shifter, add upgraded pulleys with sealed bearings such as Performance or Carmichael brand, and use loctite on all screws including limit screws and b-tension screw. Perhaps add a cover "shield" or one of those brackets which come off low-end bikes that guards against bent derailleurs from a dropped bike. The freewheel also adds some measure of protection because if the chain "locks up" the motor will just slip the clutch or die, and the tire-equipped wheel should just continue rolling unless the chain somehow binds the tire/wheel or eats the spokes (not likely if der. is adjusted right).

4. Friction losses and heat. I do not think these will be too much of an issue. Heat buildup could potentially thin the grease, but with hi-temp wheel bearing grease, you should be ok if the hub has seals. Properly and frequently lubricating the chain should secure against most friction loss, and since you have 7 speeds, the loss should be negligible.

5. Fit and possible tire scuffing. Answer: use wider hubs or narrower tires, or hacksaw off the flanges and sand/mill down the edges. Since the hub/roller will likely be closer to the seat tube and U bracket than the standard friction drive, the concern should be eliminated as long as the rear of the channel and motor are as well supported as in conventional mounting.

If the build uses extension straps to an existing Staton drive , the straps will have to be farther apart than the channel walls to account for the 7 speed freewheel and chain line.
Answer: fabricate a custom, wider, "1 piece" finished u-channel, or bend the extension straps in a table or truck mounted vise, after measuring for build.

I think Lowracer will be able to tell us how to build one quickly from pre-fabbed, pre-drilled shelf angles or angle brackets, and bolted on plates for the components (hub, rear derailleur, and motor and driveshaft stuff.

6. Availability of parts. Answer: looking for 11-20 tooth driver cog that matches standard bicycle chain, and can affix to a Dax/Staton driveshaft. Surely something is available commercially, but perhaps something will have to be fabricated. There are 22, 28, 32, 34, 36, 38 tooth front chain rings available for mtn bikes that have a 4 bolt pattern that is pretty small. Also, there are BMX cassette gears and trials-bike low gears and Tomi-cog single speed gears that fit 6 bolt disc brake hubs.

Re: Insane 7 speed friction roller drive with common engines (tanaka, pocketbike, etc

Another possibility I just thought of, is that the roller hub could be coated or dipped in that stuff used for truck bedliners, as a traction enhancement!

Note: from my experience, the cheaper hubs usually have wider barrels and thicker metal than "racing" type or roadie type hubs. I had a Dura Ace cassette hub from the late 80's which had a very narrow barrel, and the 7 speed freewheel hub on my current bike is straight across near the spoke holes, so a pretty wide barrel. I guess cassette hubs would also work with this plan, if the hub has a straight and wide barrel.

Re: Insane 7 speed friction roller drive with common engines (tanaka, pocketbike, etc

22 tooth 4 bolt Shimano sprocket, $3 . 50 Sprocket 22 tooth Chainring Shimano SG X: Staton Inc



I was thinking of something more like this with a keyway or set screw to match the shaft used

http://www.staton-inc.com/store/images/products/preview/0095.jpg

Re: Insane 7 speed friction roller drive with common engines (tanaka, pocketbike, etc

Sure, 5 speed freewheels are still available new, and easily found on garbage bikes from the 1960s or 1970s. I think there is a 5 speed Mega Range Shimano that came on a lot of low end dept store bikes in the last 20 years.

If the 5speed is narrow enough, it's possible it could fit inside the commercial U-channel, by re-spacing/removing spacers. What about adding short brackets to the channel that "hang" downward. This would also give a point to mount the rear derailleur! There's an idea! If you find one of the older, rectangular channels made before the new-style cutaway channels, you could easily mount the roller/hub between 2 straps extending even just a few inches below the channel. Then you should be able to just bend the stock U-bracket and QR straps enough to move the channel over and center the hub on the tire!

The only problem might be that the very short run of chain would cause intolerance of the chain on the drive cog. With a small cog though, it seems less of an issue. And the tire will only have to clear the bare driveshaft, except for the locking collar and drive cog on the edges.

camlifter said:

i've toyed with the idea of doing a FD using a 5sp hub as the roller. nurling the outer surface of the hub, don't see why it wouldn't work. less chance of trouble than with a derailer.

Click to expand...

Re: Insane 7 speed friction roller drive with common engines (tanaka, pocketbike, etc

I found this on Dax website. It says TITAN Jack Shaft Drive Sprocket 1/2in Fits
R1-R3 Titan Jack Shafts. New Style Milled one
piece. Only $9.99

I wonder if this means it fits on the friction drive shaft instead of the roller.

Re: Insane 7 speed friction roller drive with common engines (tanaka, pocketbike, etc

The sturmey 3 speed is a good idea, and might even fit in the Staton box. Cool. If you eliminate the external rear derailleur, that would improve chain line and the need for a tensioner, but maybe a guide (or guides on the sides of the driver gear) would be good.

I think the SA could take it because the shock loads are going to be majorly reduced. The high RPM of the hub and the fact that friction drives are actually constantly slipping even just a trivial amount, will prevent major abuse of the hub. How wide are SA x3 hubs? How tall is the hub barrel?

Re: Insane 7 speed friction roller drive with common engines (tanaka, pocketbike, etc

Yeah, there are plenty of hubs out there, especially mtn bike cassette hubs, with large, flat barrels and durable bearings. I am not sure how you would mount anything to the seatpost, unless it is something like this: Staton Bike Engine Friction Drive Mount Modification - YouTube

(video shows recumbent with staton drive, using extended brackets and hinges, plus spring and cable, to remote control the friction drive roller tension.)

Re: Insane 7 speed friction roller drive with common engines (tanaka, pocketbike, etc

I saw this generic freewheel hub for $9 online,



Hub Rear Alloy Ch Sf 48hx110 1S B/O 3/8 Silver 008-38500

Re: Insane 7 speed friction roller drive with common engines (tanaka, pocketbike, etc

What do you mean lock the freewheel? There is no need to. If the motor driven shaft turns a chain which runs to a conventional rear hub and rear derailleur, where the hub is used to friction drive the tire, there is no need to braze or lock the freewheel. The ability of the freewheel to coast is a benefit, so the bicycle can be pedaled a while when the motor is not needed or allowed, without raising the roller from the tire (the clutch performs this action also, but the ease of a freewheel to revolve is a much lower drag on bicycle pedaling performance.