[LJRead]

In developing the plans for a R E rickshaw, I intend to keep the structural weight very low using lightweight aircraft and boat building techniques, but even so I am planning it for two passengers plus some baggage (total added weight between two to three hundred kilos).  The drive sprocket on an R E is 18 tooth while the final wheel one is 38 tooth.  If you go down to a 16 tooth, or, alternatively up to say a 22 tooth sprocket on the drive end, how much in terms of percentage are you either adding or subtracting from the initial setup in terms of potential top speed?  I want to end up with a top speed of about 65 km/hr as compared to the normal top speed of around 90 km/hr.  In U.S. terms I want to start out with a bike capable of sustained speeds of about 60 mph and reduce it to about 40 mph maximum, in the process increasing my load pulling capability.

I will be going from a sprocket on a newly added differential which drives a jack shaft leading out to sprockets on either side and from there to a final chain drive to each wheel.  Thus I have a lot of possibilities for reducing the sprocket ratios, but am concerned to get it right as sprockets don't come cheap.

[baird4444]

LJR- I can't explain how I got this but I figure that you are going to turning about 28 or 2,900 RPMs at 40 mph with the 16 tooth primary. Check with the sidecar folks; I think a lot of them use the 16 th.
                                              - Mike

[LJRead]

Thanks Mike,

I've been doing a bit of head scratching here (no not lice) and figure I can make a very light job of the carriage, possibly an additional hundred pounds or even less, as compared to the hundred fifty or so of a sidecar. But even if it goes up to one-fifty, at least I'll be in the right ballpark.  It would be possible to make it even lighter, but then I would be getting into laminated foam and epoxy which gets expensive quickly.  I'm a little surprised that such a modest gear down, from 18 to 16 makes such a significant difference.  I suppose though that R Es are normally a little  geared down.

Larry

[cyrusb]

What drive axle would you use?  You could allways lower your drive ratio there. Either with rear sprocket size (Assuming  you wont be using the re sprocket) or with wheel size.  A sprocket smaller than 16 would be hard on the chain, but would work. Why not insert the whole bike, sans frontend into the back of the rickshaw, and everybody sits up front?

[LJRead]

I'm studying axle options now, and any advice is appreciated.  Current thinking is to use the lower swing arm, shocks, and entire rear wheel with sprocket, one off the existing bike, the other to be scrounged or purchased.  I would use a differential/jack shaft setup with sprockets at either end, and these in turn would drive each wheel.  I would thus have very stiff independent suspension (swinging arm) on each wheel.  The only problem is the cost of a complete wheel, swinging arm, and shocks.  This type of setup was used in automobiles at the turn of the century (around 1900) except that a transmission had two stub axles going out on either side with sprockets at the ends, and the rear wheels were simply attached to a dead axle, like on on old wagon, which they were derived from.

I found a good, inexpensive, but sturdy differential (Comet SCD-1) which is used in dune buggies.  But normally it is attached to a live rear axle with universal joints, shocks etc.  Thia is another possibility.  I like the idea of using separate sprockets and chains for each wheel, and the R E system gives good chain adjustment capability  I contacted Jim at CMW, hoping to get a quick response as to cost of a rear wheel and so on, but it has been several days and no answer.  Probably pretty busy.

One nice thing about the separate chain for each wheel idea is that it allows the rear seat to be very low, since there is no sprocket etc. to get in the way, but since the rear sprocket could be buried beneath the seat, it isn't that much of an advantage.  If you look at the R E Pilot, you see that the rear box is quite high because of a substantial sprocket.   

[LJRead]

Interestingly  enough, the drive sprocket on my Thunderbird is 16 tooth, and possibly this is standard with the smaller 350 cc engine.  Therefore, the easiest thing to do is to use a drive sprocket on each end of the jack shaft, getting my gearing closer to the rear wheels.   Perfectly acceptable.  CMW sells a 22 tooth drive sprocket, which would give a 22 tooth: 38 tooth gearing.  Maybe a bit too low geared, and maybe using a 27 tooth to the 38 tooth gearing would be closer.  A little on the low gearing  side would probably be wise with the additional weight.  Putting along at an even lower speed here seems ok to me!

Whichever tooth size I decide on, I will only need to purchase two sprockets for now.

[baird4444]

Larry-  the estimate of RPMs that I worked out was based on
a 500. I forgot that the T-Bird is a 350....   
don't know how correct my ciphering will be.
                                 - Mike

[cyrusb]

Your numbers should be correct for both engines.I believe the primary drive ratios are the same for both bikes,  and last gear should be 1 to 1 (locked up mainshaft) for both transmissions.

[LJRead]

I only counted the teeth on my drive sprocket which could have been a replacement.  I'm wondering though if I'm not asking the wrong question.  How much power is needed or can be brought to bear in the lower gears when getting the trike moving?  That is, without having the clutch slipping.  It would be nice to have compound gearing so that a high and low range could be put into action.

[luoma]

The smaller the front sprocket, to lower geared it will be. I figured it out mathematically onece and found that a one-tooth difference in the countershaft sprocket equaled about 3 mph difference in fifth gear (that does not always mean additional top speed. too many other factors). Goind down as small as you can on the front cog will give you more power, less speed. Sounds like what you want. You could also go for a bigger sprocket on the rear wheel.

[LJRead]

I'm as small as you can go on the drive sprocket (16 tooth), but what I intend is to go from the drive sprocket to the differential (Comet SCD-1), which is a well supported jack shaft, and from there to sprockets on either end which will drive the wheels.  I'm going to keep the 38 tooth sprocket on each wheel for reasons of economy, if nothing else,, so I have the two options, perhaps a 50 tooth sprocket on the differential, and keep all other sprockets (outer jack shaft and rear wheels) at about the same tooth (38)  I think a fifty tooth sprocket on the differential will give me about what I need, perhaps a top speed (with a little extra for emergencies) of about 40 to 45 mph.  If I don't get it right, I will only have to change, up or down, that single sprocket.

The ground clearance of our bikes is about ten inches under the engine, while the wheel axle is about 16 inches.  By having the jack shaft, a lower trike carriage is then possibly, permitting a lower seating arrangement (low center of gravity) and very good storage space.   It also divides the chain lengths into two parts (engine to diff. and jack shaft outer sprockets to wheels), and, by using the R E swinging arm system, I will have independent suspension on each wheel, and easy chain adjustment through sliding the wheel back as in the normal bike setup.

Sorry to go on like this, but this is an exciting time for me as I think over what needs to be done. You know how it is, you get excited and want to share your excitement, but here there is no one who wants to hear, and, at least if you of the forum aren't interested, you can tune me out