Super Tigre S29 Ringed

Any explanation for the off-set intake? First one I've seen that's not central, though I'm not at all familiar with Super Tigres.

Has something to do with balance and timing, The combat supertigers I've seen also have the offset boss.
(Bandit)

This is a Super Tigre engine and not a Como. I believe that the Como engines were only distributed in the U.S.A. although manufactured by Super Tigre. The Como engines have a good reputation but I have only come across 40s and 51s but have no experience of them running.

This 29 uses the same crankcase as the X.21 and X.25.

http://sceptreflight.net/Model%20Engine%20Tests/ST%20S.29%20RC.html

The reason I mention the lightness of the silencer rather than its efficiency is .....

back in the 60's we were scuppered by being forced to add silencers to our engines. Then I had an Enya 15 and I was pleased with it but after adding a very heavy Enya "strap on" my plane wouldn't even lift off the ground. Not only the weight but the restriction of the silencers rendered quite a few models useless.

This would have been an attempt to directly replace a smaller engine and keep the weight down. Even then, this is still heavier than the OS 25 LA but a lot lighter than a PAW 29.

I have a Super Tigre silencer that is bigger and lighter - much of the body is spun aluminium and not a casting and the nozzle is replaceable. It is on my ever increasing list of things to try.

The offset inlet is normal on these intakes

This is a G15



The unusual is the rectangular venturi. The S 29 engine I have shown was originally and RC engine - the previous owner nabbed the carb for another engine. That's how I ended up with this engine.

So a couple of minutes on the lathe and another couple on the milling machine - venturi fitted + spare NVA! One day I will do a rectangular one!

The MVVS engines also had offset intakes



I haven't seen a sub 2.5cc engine with an offset intake yet.

Many engines have the case front venturi opening dead center but there are several with left or right of center positioning

I imagin.. (never have read any discussion on the design constraints) it depends a lot on the total timing of the "Intake Window" relative to the stroke, perhaps an attempt to not have all the weak points of the crank lined up Dead Center, or in my mind, maybe a well thought out air/fluid flow pattern to optimize intake charge

Opposed to this ST, with casing opening on the left (viewed from front) ---Many combat engines Like Nelson have the position in advance...on the right viewed from the front

I did read with interest several discussions (long lost downloads) on small engine 2 stroke optimization where the engineer deliberately cast the crankcase such that the crankshaft bore, fore to aft, was ever so slightly offset left or right ( on the order of only .001~.002 relative to the center line of the Piston/liner UP/Down bore-----to insure that Connecting rod at Top Dead Center did NOT produce a power stroke directly DOWN...in other words Top dead center of the piston- relative to the crank pin was slightly offset so the crank pin was not directly in line with the piston / liner bore and already was "over the top" so the power stroke was not partially wasted

fredvon4 wrote:
I did read with interest several discussions (long lost downloads) on small engine 2 stroke optimization where the engineer deliberately cast the crankcase such that the crankshaft bore, fore to aft, was ever so slightly offset left or right ( on the order of only .001~.002 relative to the center line of the Piston/liner UP/Down bore-----to insure that Connecting rod at Top Dead Center did NOT produce a power stroke directly DOWN...in other words Top dead center of the piston- relative to the crank pin was slightly offset so the crank pin was not directly in line with the piston / liner bore and already was "over the top" so the power stroke was not partially wasted

Are you referring to "desaxe" ?
If so, I think the idea is reduce the friction on the power stroke, it also changes the timing of the engine as it no longer will be symmetrical. The crank pin will always be "inline" with the connecting rod at TDC though, that sort of defines TDC in relation to the crank rotation.

The X.21 is similar in design. These engines also have the Super Tigre porting, STS, with four transfer ports of similar height rather than the typical schnuerle with one lower boost port.

(I was going to put a few pictures here but it doesn't seem to work at the moment...)

Those STs are apparently fine stunt engines. I suppose they make a 35-46 size too? I might have to try one some day.

Rusty, any of the series X are generally timed too fast for stunt. If you ever decide on using one, the V variants are the stunt engines. In a .35 size, the G-21 C was made with a baffled piston. Any of the flat top piston engines are out, they're combat engines. The .46, .56, .60 were the staple engine for quite a while.