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Just what do the letters "OP" stand for? Tbuelna - Yes, I would regard hydrostatic drives as "positive" (except perhaps for a bit of leakage past the pistons etc). I think some hydro. drives (in fork lifts, lawn tractors etc.) are arranged so that the speed range is from zero upwards - so...

Ivymike - I agree with you to some extent. However a lot (maybe most?) major advances in engineering start off as academic/theoretical "researchy stuff". PP - You are right, nothing will break exactly on the 1:0 ratio as there is no motion (this being right on the "neutral" point) - however as...

GregLocock - On the question of moving away from a standing start - any continuous gear ratio range can be arranged by overall biasing to have an infinitely low (1:0) starting ratio. It can even be arranged so that the ratio range is from negative values (reverse direction that would be)...

I have no connection whatsoever with BYU, not being a Mormon and living on a different continent. I was trying to draw out some specialised comment on the variable gear subject from engineers who have worked in the theoretical PECVT field (and there are some). But it doesn't look like it is...

Ivymike - Thank you, that does just about sum up what I was originally asking. However, my simple answer would be that it is highly likely that it is a theoretical/physical impossibility - so we have slightly different points of view. Positive engagement continuously variable transmissions...

GregLocock - could you further explain what you mean in your last posting? Is the "no slip" you refer to the slight amount of sliding (as opposed to rolling action) that occurs when two gear teeth engage?

I think an ideal variable gear system must be able to operate in both directions through the "gearbox" - with the reverse direction being the inverse ratio as with conventional gear sets. Once again with pushbikes, they usually freewheel on the overrun so ratchet-type arrangements would be OK.

Ivymike - If you use a uni-directional roller clutch you can achieve infinitely small steps. Oscillating systems that are "rectified" into a variable uni-directional output are one of the main groups of suggested variable gear mechanisms - there are thousands of examples in the world's patent...

GregLocock - these are very serious stipulations. I am only interested in mechanisms of this type. Despite many claims to the contrary I don't think it can be done - but it is very difficult to prove a negative etc. Despite many years of interest in the subject I have never seen anything even...

"Mechanical fish wrappers" - ??

Sorry about the lack of links. This is a very specialised subject and I was hoping for some really specialised comment. We are considering a similar academic exercise to that of BYU. What comment I get may influence whether the study goes ahead or not...

I would have thought this subject would be a FAQ - but apparently not. I have always wondered if an "infinitely variable gear" is possible. I am not referring to any of the currently commercially available CVTs etc. but a constantly engaged, positive drive, all teeth and chains (or whatever)...

I have to admit that sabotage did occur to me too. It does happen.

Dirk489 - What kind of car/engine is it? You mentioned "Slmson" - did you mean "Salmson"?

I may be missing something obvious but how does sand from the sump casting get past the oilpump pickup screen and the engine's oil filter? Some cars (like the old Morris Minis etc.) had enormous amounts of metal chips, shavings and assorted rubbish in their sumps and this never got up into the...

To get back to Mechanic6's original question - if this is just for an interesting project, maybe he should work on a steam/hot water (very hot water) storage system. This is in the sense of the old "fireless" steam locomotives. These locos could usually work a full shift on the one charge of...

The V12 Lagonda of the late 1930's had aluminium rods acting directly (no bearing shells) onto hardened crankpins. Some SS, Mk. 4 and 5 Jaguar engines also had aluminium rods - but I don't know if they had bearing inserts or not.

Mr. PW - I think "personal entertainment" is a perfectly good reason for doing something like your project. However, what is your main aim - interest in building the engine or results in running it? If it is mostly the running aspect, I have found from similar projects that (surprisingly) it is...

Mr. PW - You say that supercharging of a two-stroke has been done successfully by pressurising the intake and throttling the exhaust to match the intake pressure. Do you have a reference to this somewhere? It seems like a very simple and practical method to me and I would like to actually try...

Interesting point Fireslave is making. A 2-stroke engine operating at sea level presumably makes a lot more power than the same engine operating on a mountain at 10,000 feet (for example) where the atmospheric pressure is 20 inches of Hg or thereabouts. When the engine returns to sea level it...