Completed Twin Inline IC Engine

[John OlsenParticipant @johnolsen79199]

Most four stroke model aircraft engines simply rely on the oil in the fuel to lubricate all of the engine. It might seem a bit sketchy, but remember the fuel has much more oil in it than would be typical for say a modern two stroke motorcycle. A three to 1 or four to 1 mix is pretty usual. So there is plenty of oil around and much of it manages to make its way into the crankcase. Even where big ends are plain bearings they last well.

There is an interesting situation with ball and roller bearings. They either need just a bare minimum of oil, like they get with a traditional two stroke, or, if they are to be fed with oil from a pump, they need a high flow. What you must not do is allow the bearing to be full of oil that cannot escape. The oil will churn and the bearing will overheat. Phil Irving discussed this in his book on motorcycle engineering. So provision should be made for the oil to be able to flow through freely.

The 180 degree crank is awkward from the spark ignition point of view. With the 360 crank you can use a double ended coil and a waste spark on the exhaust stroke for a nice simple setup. Honda did this on the 175/200 twin, which did have a 360 degree crank, and used two of them on the fours. You can't do this on a 180 crank like the 350 had. From a balance point of view there is little to choose either way, the 180 crank gives a rocking couple which can be just as much nuisance as the unbalance from a 360 crank.

The Honda 50 stepthru also used the dipper system for big end lubrication. Larger versions of that motor like the 90 had a pump.

John

[Mick B1Participant @mickb1]

Posted by John Olsen on 04/01/2019 20:39:50:

Most four stroke model aircraft engines simply rely on the oil in the fuel to lubricate all of the engine. It might seem a bit sketchy, but remember the fuel has much more oil in it than would be typical for say a modern two stroke motorcycle. A three to 1 or four to 1 mix is pretty usual. So there is plenty of oil around and much of it manages to make its way into the crankcase. Even where big ends are plain bearings they last well.

…..

The Honda 50 stepthru also used the dipper system for big end lubrication. Larger versions of that motor like the 90 had a pump.

John

Thanks for that – all clear now. I didn't know about the high oil content in the mix, I could see there's not really room for wet sump and splash, and I guessed aero-engine revs would (typically) be rather higher than a lawnmower…

[not done it yetParticipant @notdoneityet]

My CD175’s and my brother’s CB160 only had one set of contact breakers, I am sure, and was driven at the usual half crankshaft speed (from the camshaft) but there was no distributor. So it must have had two coils and thus a wasted spark at every break? Amazing that I never gave it a thought in my youth. The bikes just went so well and we rode the socks off them. The 175’s did not handle too well, mind! A mate’s 250 James either went around or inside on the corners, while the Honda misbehaved.

[peter gabriele 1Participant @petergabriele1]

I have just received plans for the twin inline ic engine,but there isn't any build information, i.e. valve/ignition timing,are in &ex cams the same etc?

Peter

[Ady1Participant @ady1]

Lovely work, really lovely

My 2CV engined citroen visa had one coil and a sensor on the flywheel

It fired 2 sparks per stroke, so one got wasted, it was a supersimple superreliable system

[JasonBModerator @jasonb]

Peter the other engines in the series( Vtwin & Boxer) that I have drawings for don't have different profiles for inlet and exhaust so should be safe to make them all the same.

As it uses glow ignition you have no way to control the ignition timing it will just fire when the fuel/air mix is compressed enough.

valve timing suck it and see unless Steve comes back with how he set it.

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