Thanks. I guess what I am not understanding is how the roller is secured to the jack shaft in this application. And the jack shaft is not keyed, correct?
HF 2.5 Friction Drive- A Different Approach
- Thread starter cannonball2
- Start date
It is compressed on the jackshaft and driven by, yep friction. The jackshaft is drilled and tapped for a bolt. A lock collar is positioned and a hole is drilled for the set screw in the shaft. Once its all assembled in the bearings the bolt is tightened to pull the jackshaft into compression on to the roller. The advantage to this roller set up is you can make/try any material you can hole saw, no keyway required.
I tell you what Cannon, If a guy wanted to go friction instead of pulley like my Mongoose, Your setup is a small revellation as far as friction drive. One of the biggest problems in that type of drive system is "building,desideing, buying" what to use as a roller. Not to mention expense. Now with your compression roller/jackshaft system idea, if a guy has got the tools he can make his roller any size for a ratio change (then relocate your rack mounting point). And he can make it out of most anything as far as material. For that you have to consider what gets you the best roller traction per tire wear. But I say you came up with one of the most cost and time effective ways to experiment with friction drive that gets an Idea from the drawing board to the test track the fastest and cheapest IMO from experience building friction drive bikes myself. 
Thanks for the positive comments 4950. I have pretty much settled on direct drive for my FDs, The auto clutch/jackshaft build is the easiest to ride, my wife loves it. But for my personal taste I just like direct. That way I am only dealing with the engines shaft. Ratios can be changed in a minute or less, and I have three rollers for my "traveling" bikes that stay in the bikes bag. I have a 1.9 for mega hill country/trailer towing, a 2.125 for general use a good hill climber and top speed(34mph), and a 2.5 speed roller which tops right around 40mph if I ever should make the flat country. I also have a emergency use rain roller, drives well in the wet, even standing water, but not too tire friendly. I have belt and chain drive bikes also, but the FDs have been just been so darn reliable, that when I venture far from home thats what I am on.
Sorry for being dense. I understand if it was a direct drive and the drive shaft was tapped how that would compress the roller on the shaft. But if the roller is on it's own shaft with bearings on each end, is the roller material just compressed between to lock collars like the diagram below, or what am I missing here?
Sorry for being so dense. Is there a collar on each side of the roller? I understand how the roller is compressed if it is just on the drive shaft of the engine with a tapped shaft, but if the roller is on it's own shaft will pillow bearings on each end, what is compressing the roller so it does not spin on the shaft?
i.e. does a collar on each side of the roller material keep the roller compressed like the diagram below? I must be missing something.
i.e. does a collar on each side of the roller material keep the roller compressed like the diagram below? I must be missing something.
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Thats a nice diagram! The shaft dimensions are determined and the collar is the fixed point (anchored with the set screw in a drilled depression) on one side of the roller, the shaft comes to about 1/2" just inside the non drive side pillow bearing, that is the drilled and tapped end. You insert a bolt with a washer(washer bears on the bearing race) into the end of that bearing and draw the shaft to the bolt compressing the roller. If using a hard roller like oak, insert a disc of compressable material like hard rubber allow a good deal of compression and friction surface to drive the roller. It sounds more complicated than it actually is. It takes a bit of "set up" to determine spacing , spacers, washers etc. Once all that is worked out, you can add any kind of roller/material that will fit.
Thats pretty much it. Since I got the bike out for pics I took it for a short ride, hadnt ridden it in a while. What a nice smooth, easy to ride machine, no wonder my wife likes it so.
Yeah looks like a great setup. I was going to get a new recumbent next year and do a MB conversion on my current short wheel base recumbent, but after load testing with some dead weight on my rack it is just too squirlley since the frame is a single "stick tube" there is too much flex. Now I am tossing ideas around, thinking about the using the predator 99cc in-frame (standard triangle frame) with a clutch, then driving a friction drive kind of like yours with either turnbuckle or thumb screw tension adjustment, with a belt and tension idler. Need a good winter project and this should be a fun build.
An advantage with the belt drive is once your roller is situated you can change the ratios with the driven pulley, pretty much like swapping rollers. A spring loaded idler make pulley changes a snap(haha).
Sounds good. I would build one myself if I didn't like the Mongoose so much. I have a buddy that needs an MB real bad. Maybe I'll run with your idea Cannon if you don't mind ? John
Thats what its out there for John. Improvements are welcome, post any you come up with.
Thanks for all the help. One thing I'd like to ask you guys with some experience about is roller size for FD's. I have been playing around with drive ratio math... obviously the clutch diameter is fixed, but we can play with the sheave diameter on the jack shaft and/or the roller size.
if you had to pick the ideal roller size, what would you pick? or does it matter much? would there be an advantage of a 3" (or larger) roller over a 2" roller assuming the final drive ratio was kept near the same?
if you had to pick the ideal roller size, what would you pick? or does it matter much? would there be an advantage of a 3" (or larger) roller over a 2" roller assuming the final drive ratio was kept near the same?
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The thing that determines roller size for me is hill climbing ability, so I stay below at or below 2.5 for my direct drives. The larger rollers are more efficient, and with a belt drive you can run a larger roller and adjust pulley size until the driven pulley size gets to be too big to be practical. What horsepower engine are you going to use?
Going to use the HF predator 99cc. Sounds like the bigger the roller the better (within reason). Might even go with a 4" roller for that matter.
Not a significant factor... does the roller diameter matter much even if so? I would think hill climbing performance would mainly be a function of the final drive ratio.
I think its best to think in terms of direct drive, in other words, whats the biggest roller a 3.5 hp engine will practically use. If its say 3" and you go 4 you will have to under drive it, so the only advantage is the efficiency of the larger slower turning roller. If you ran a 4" reduced 2:1 assuming an engine rpm of 5000 top speed is right at 30mph, not bad. Assume a clutch engagement of 2000 and its a pretty tall pull off as the roller speed is 11.5mph from stop. My direct bike with the 2.5" roller pull off speed is 9mph with a top speed of just under 40. Rollers are a trade off, takes some experimentation to find the most practical speed envelope for the riding desired. If top speed is the goal then a big roller, just dont plan to slowly ride down a gravel road say. This of course changes with an auto clutch, it will slip until the roller speed matches road speed. My belt driven bike runs a 2.25 roller, with that it has a decent top speed, around 32mph at 4800rpm. climbs hills well and pulls away very nicely with out pedaling. Thats at a 1:1 drive, I can still over or under drive it as necessary. Wayne has the hot lick with the 2speed, thats what you need with a bigger than direct drive roller.
