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

happycheapskate

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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! brnot

Today, 06:04 PM

happycheapskate
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Join Date: Nov 2009
Location: Far Worse TX
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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.
 
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happycheapskate

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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.
 
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camlifter

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May 4, 2009
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Re: Insane 7 speed friction roller drive with common engines (tanaka, pocketbike, etc

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.
 
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happycheapskate

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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.
 
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happycheapskate

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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. :-||



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.
 

happycheapskate

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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.
 

silverbear

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Jul 9, 2009
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Re: Insane 7 speed friction roller drive with common engines (tanaka, pocketbike, etc

Just throwing this out there, but what is the likelihood that one of the old sturmey archer 3 speed hubs would hold up to this kind of use? Too wimpy? I would think that three speeds or perhaps five would be plenty enough if one is shifting gears while under power. Most of us are not interested in breaking speed records, but just want to be able to start off and climb hills without pedaling and be able to cruise along at 20 or 25 without straining the engine. Maybe more gear choices are needed to get things in the right gear range, something I know less than nothing about. An internally geared hub as drive roller has potential, I think. Making it grab the tire is probably the easy part. I like the idea and will be interested to see where it goes.
SB
 

cannonball2

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

I have a 7spd Shimano internal hub I have been saving for just such a project. It even has a form of intergral disc brake. Have been toying with modding the belt drive Fd I already have, would not be a big conversion.
 

happycheapskate

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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?
 

silverbear

The Boy Who Never Grew Up
Jul 9, 2009
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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?
The couple I have are back in Minnesota (I'm in Maryland for the winter), so I can't measure anything. I also have a two speed Bendix hub from a middleweight Schwinn Corvette that used a cable shifter (not the kick back hub. It seems to me that one of the 3 speed Sturmey's is free wheel and the other is coaster brake. There isn't much interest in a 3 speed skinny tire bike anymore, so I would think one would be pretty cheap, like from a freebie bike. The 3 speed shifters were both of the thumb control lever type and also a throttle twist grip. I liked the twist grip type shifter.
SB
 

cannonball2

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

Checked out the 7 speed hub and its a no go. Not well suited by its hub design being stepped. Also the sprocket seems intergral to the hubs workings not the usual freewheel, which is a problem as the FD drives in the direction of its freewheeling.
 

cannonball2

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

Ya know if the derail hub was mounted at the base of the seat post you would get a longer chain run to be able to shift the chain, also the post would make a nice place to mount the derail. An FD would be enhanced by as few as three ratios. a 5 speed would be plenty I feel. A very simple version is to just have a spring loaded idler and manually shift the ratios(greasy fingers) as conditions demand. Certainly not as nice as shift on the fly, but very quick to do in a few seconds. I find that a properly sized roller for general conditions has a good operating envelope. My general use roller climbs major hills well and criuses nicely at 28 mph, which is fast enough to get somewhere. It would be nice to shift up to a higher ratio on demand, but I would not need to down shift unless climbing in the Rockies or something. So really a 2sp is adequate fo the most part, and Waynes covered that. I would like to be able to do that in a somewhat simpler fashion. Not trying to throw a wet blanket, I like the multispeed idea With enough of us thinking it over we are bound to come up with something cool.
 

happycheapskate

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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.)
 

cannonball2

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

Not the seat post. Actually the lower frame legs behind the seat post in front of the tire, basically like a jackshaft. A simple bracket bent into a square "U" to hold the rear hub against the tire, welded or maybe even U bolted to the frame rails. Also if a large mulit speed casssette is used to avoid over throw the derail can be limited by its stops not to select the first and last gears, so a 9 speed becomes a 7, a 7 a 5, etc. I have never had a issue with my shifter bike in the reguard, so dont see it a problem to use the full range. How are you going to lock the freewheel, brazing seems like a good method.
 

happycheapskate

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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.
 

cannonball2

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

Maybe Im confused but the roller must turn CCW to drive the wheel foward. Wouldnt the freewheel just spin?
 

happyvalley

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

Not trying to throw a wet blanket
Not a wet blanket CB discussing practical pro and cons, at least I hope not.
To me the beauty of friction drive is the simplicity, no chains belts sprockets pulleys, plus I can swap it off one bike in 20 minutes and onto another in 30. The simplicity can balance out the downsides of efficiency losses, slipping in wet weather and accelerated tire wear.

To then complexify that simplicity with cables, added weight, chain and sprockets to only end up with a.....friction drive.....and it's inherent downsides might seem to me to be not gaining a lot but losing some.

Going to the trouble of multi speeds and adding chains to the equation I think I might just want to stick with chain for better efficacy, able to ride in all weather and better tire wear.

Staton does this, 7 speeds and a tricky dérailleur. Is it worth it, I don't know but probably not.

1525.jpg
 
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