RCV Engines

I don't have personal experience, but I watched a fellow club member breaking in several for multi-engine models with slender cowls. The main thing I noticed is that he said he could only get it to idle down to 2000 RPM (prop RPM). He was getting 5500 RPM max with I don't know what 3-blade prop.

I would have expected idles of about 1000 RPM to be practical with the 2:1 reduction between the prop and the crank. I asked, and he said that this did not work out.

If there is good compression, this might be helped by an onboard glow lighter that comes on at low throttle. In any case, the idle was the problem - the motors seemed to work well otherwise.

-- Mike Norton

A 1000 rpm idle at the prop would require the motor to be effectively running at 500 rpm, which seems a little low to keep the plug hot etc. Perhaps that is the limiting factor so the plug driver may well help there.

I think the 2:1 ratio works the other way:

I could be wrong.

Marty

Other way aruond. It has a reduction gear on the output shaft - if you like, it's driven from the camshaft :)

An RCV engine has no camshaft. RCV stands for Rotating Cylinder Valve. The bottom of the cylinder is geared to the crankshaft. Intake, glow timing and exhaust valving is supplied by ports at the top of the cylinder. But, you are right about the speed. A 1000 RPM idle translates to 2000 piston strokes. I suspect that a hotter glow plug might help. I use an Enya #3 in mine. The idle does improve with running.

Jim - AMA 501383

I think he said that for illustrative purposes. I understood what he meant.

You are not wrong.

I believe the 2:1 works the other way. The crankshaft is turning twice the prop speed.

Dan Thompson (AMA 32873, EAA 60974, WB4GUK, GROL) remove POST in address for email

At the risk of being flamed, RCU has an RCV support forum. Factory rep answers posted questions pretty quickly.

Who isn't?

the guy that said the crank was turning 2 times faster than the prop.

Ohmigawd. He missed the smiley...

I know that.

Alright. Let's take the smiley off and rewrite IF YOU LIKE, ITS DRIVEN BY THE VALVE OPERATING SHAFT.

Which in a 4 stroke, has to run at half crank speed if there is one complete induction/exhaust cycle per valve shaft revolution.

Happy now?

:-)

Other thing Ive heard is they vibrate like an SOB...rubber mountings mandatory.

Not hugely powerful eiher.

For those who love their IC engines teh very most amazing design I have seen - it was suposed to be for racing, but has never uyet seen the light of day - was an 8 cylinder double H configuration using rotating sleeve valves as per RCV.

Basically it has two counter rotating cranks geared together and each one is essentially a flat four - so the basic concept is a flat four stacked on another one running backards and geared togeher.

The sleeve valves were I thing geared direct off the crankshafts,

A 4 liter engine was not much bigger than the laser printer on my desktop. The whole exrecise was in getting rid of wasted space and metal in an IC engine. As you can imagine, apart from the plugs, there is nothing sticking out for the basic engine.

The designers was futilely trying to get someone to fund it - would have made a great road engine for a tiny car tho, scaled down to 800cc or so.

"The Natural Philosopher" skrev i melding news: snipped-for-privacy@b.c...

Rubber mountings are definitely NOT recommended.

RCV has made a metal mounting plate that will go behind the firewall in order to beef up the engine mount.

The engine will vibrate if not mounted securely on a very rigid firewall.

This is due the much higher than normal torque from RCV engines.

Yep - no smiley on my copy! I thought you were serious.

Jim - AMA 501383

The Natural Philos>

In other words, the engine still vibrates badly but the airframe is now asked to absorbe it!

Well, the general idea is that the engine does not vibrate badly. But if you let it start to move around, like it would be able to on rubber mounts, the torque will amplify that movement into a bad vibration.

Kjell Aanvik

"Paul McIntosh" skrev i melding news:bn9jpv$1fm$ snipped-for-privacy@hercules.btinternet.com...

Not my problem.

Not my problem either, but if true, I sure the APL and a bunch of Universities will be studying it in the near future... Breakthrus in physics ALWAYS come from small, unknown shops... Roger W Guinn, PE

The Natural Philos>