Build of 3 Speed Friction Drive

graucho--I spent 43 years working as a mechanical design engineer doing exactly the things you mentioned. I don't fish or golf, so when I retired last spring I decided to spend some time building a MB and now I'm hooked on it. All those photos you post are great motivation.

rawly--I agree, if it worked the first time, it wouldn't be worth doing.

One of my objectives is to make a MB that does not attract attention, so I need a quite muffler. I looked at bunches of automotive mufflers on the Internet and found one that looked like it could be scaled down. The body is 3-in dia by 9-in long. The inlet and outlet tubes are conduit. The exhaust noise is substantially reduced, but still too much mechanical noise.

Eventually, I will be trying to make an enclosure which will look like a trunk and hide the drive train as well as absorb noise.

I added a speedometer and took it out for another ride. In the middle gear it cruises easily at 22 mph, even up small hills. In high gear it quickly got up to 26 mph, if the road was longer it would have gone a bit faster.

I will be setting this project aside for awhile. But, will definitely have more to post before spring.

011121213Muffler.jpg

012121213Bike.jpg
 
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Lee,
I too have looked in making a better muffller. It lead me to a site that made mufflers
with reciprocating disc baffles similar to the sort used by seals on inflatables. My
version didn't work all that well largely because I over thought it. Then I saw a video
of a fella the had built a jack shaft bike with a GX35. It worked well, but seemed excessively
complex to me. The thing that stood out was the muffler. it was a simple tube coming
down from the exhaust with a metal L.L. Bean water bottle suspended by two springs
from the tube, the opening on the bottle being larger that the tube dia. Instead of discs,
the whole muffler reciprocated. It was hard to tell how effective this was cuz a gx35
is quiet to begin with, but i thought it was very clever and seemed to work well.
I don't mean to disparage of your 3 spd, but it seems bulky and complex. I've been
thinking more in terms of a CVT. Perhaps a cone shaped roller that moves across the
tire to change ratios. Thoughts?
 
Lee, variable speed direct drives, ever heard of the Serwa motor? 1940s French.

serwa_auxiliaire.jpg


rallye_serwa_8.jpg


The rollers pressed outwards on to a dummy belt rim.
 
That seems a relatively simple mechanism. I think it would be even more so
without the sheave,and inverted thus acting directly against the tire. Still, I'm
thinking something even simpler. Fewer parts the less to go wrong, less
mechanical drag on the engine, lighter, less costly, less labor intensive. C'mon
Lee, you can do it.
 
Those are all interesting comments and I have actually thought about those concepts. I do not always go into detail because the detail is often not as interesting to others as it is to me.

First, to explain my limited understanding of a muffler which has these operational characteristics.

In a four stroke engine the muffler must not excessively restrict the flow of exhaust gasses. I calculated the flow area thru the inlet and outlet tubes as well as all the baffles and designed this muffler to be less restrictive than the original box muffler. Also notice the long inlet tube (header) which allows the exhaust gasses to flow freely from the engine to the first internal restriction. I don't actually call it a header because I did not try to match it to the engine.

The next muffler function is to smooth out the gas flow from a series of pulses to a smooth continuous flow. In the photo you can see there are four chambers. The bottom chamber is closed and acts as an air spring. The next chamber up is for expansion. The gas enters thru various lengths of passage so the pressure peaks arrive into this chamber over larger time span which smooths out the flow. An so forth for the other two chambers.

And a muffler is also a noise canceling device. The noise from combustion is carried to the chambers thru the assortment of holes. The noise is reflected inside the chamber so that some reflected sound waves are out of phase with other sound waves and cancel out. This is pretty much random, so the more holes and chamber, the better.

Anyway, right or wrong that's the way I see it. And that's why I made the muffler as I did.

I like the cvt ideas, but I'm tired of thinking, so will comment on those another day.
 
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I think I follow your remarks. Where there supposed to attachments illustrating
your text? I understand performance relies upon a uniform flow into and from
the combustion chamber. still there needs be a certain bit of back pressure to
maintain heat in the chamber. It's a fine line. What intrigues me about a reciprocating
muffler is that it works like a shock absorber for sound catching each explosion
and absorbing the force.
Would that I had your tools and experience,... and resources?
 
Production products use gear drives which are much more compact. I am limited to belts and chains. I like belts for high speed because they are quite. They both require big center distances compared to gears. The two speed inside roller drive is very clever and well done, looks like it uses gears and is beyond my abilities.

I did consider a similar concept with two separate rollers that could be engaged onto the tire, it was bulky, and I thought it would be difficult to control its operation

rawly--I did spend time thinking about a tapered roller just like you suggested. I did not come up with a good way to move it side to side as well as up and down. But, I believe this concept could be made to work. It reminds me of snowblower drive trains where a rubber roller is moved across an aluminum disc. I also thought about a stepped roller with 2 speeds, again the control mechanism gets difficult to build.

The Sturmey Archer 3-speed is easy to shift (I didn't have to build any special controls). And it has a built in freewheel which allows the bike to be ridden with the motor turned off. On the downside, the freewheel required the weird starting mechanism which bypasses the S/A freewheel.


Here's a sketch of the muffler with the flow areas. Also a link to a forum where an auto muffler is disassembled and discussed. I felt scaling down an auto muffler gave me the best chance of success. I liked this design because there were only two internal tubes (most mufflers have three).
http://www.clubfrontier.org/forums/f23/2006-nissan-frontier-stock-muffler-cutaway-view-69578/
013121214MufflerSketch_zpsaa10e30b.jpg
 
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I prefer belts myself for the same reason. Your muffler appears
to utilize to the same volume and distance as those commercial
expansion chamber yet requiring considerably less space. It is
in many respects similar to the one I built using reciprocating
discs. I just pulled it back out of my parts bone yard before
reading this. I plan to try it again with a couple new mods, Like
yours, it is compact. Earlier it had worked fairly well, but I put
it aside when I got involved in another project.
I think that by canting a typical FD channel at an angle with
a tapered roller in it, it should be simple to make it pivot across
the tire by means of a lever.
 
P.S. My muffler is T-shaped splitting the gases into
2 larger chambers with holes and soft, heat-ablative diaphragms
that oscillate at engine frequency without restricting flow
thus neutralizing sound. I had used steel tube for the larger
chambers, but I think non-metallic tubing would work better.
 
Hi !

Your bike is just FANTASTIC!

I do agree with you on friction drive, Simple and Reliable !
I personally successfully glued emery cloth grid 60 on my steel roller, and I now have no slippage, even with a wet and dirty tire. Amazing results I must say, way above my expectations.
A little video (in french... sorry) http://www.youtube.com/watch?v=xb8bWyc-ky8
I also tried the rubber roller with success, but it is terrible when the road is wet, and hi power engine just burn them...

I have ordered a 3 speed hub a few days ago, and I plan to use it on my chainsaw motored bike, with emery cloth glued to make it abrasive.

I was wondering if your bike still perform well, and if there is a problem with the hub strength?
What about gear changes?
Have you done some videos of it running ?

Bye.
 
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