VF 40 is a good one, what about....

OS 40 VR-P ABC,

It looks like a vf 40 but the venturi is in the back plate.

Anyone try one?

Doug,
Generally speaking rear intakes are utilized on engines intended for maximum performance. It allows a much longer intake duration without unduly weakening the crankshaft. It is likely the engine was intended for pylon racing or some other max performance event.

I've no personal experience with the engine, however.

Ted

Doug,
Th 40VR-P was made and intended for pylon racing. I have two of them and used one on a Rat some years ago. They have huge ports, very high exhaust timing and are intended to run small props at 22,000+ RPM. Not your Sunday Best stunt setup. They were made in both ringed and lapped versions.

Can you say "SPEED STUNT".....Maybe a "1" pitch prop....

Randy C

Ohhhhhh, me like 'em 22000 RPMS!!

Thanks for the info guys.

>Ohhhhhh, me like 'em 22000 RPMS!!
>
>Thanks for the info guys.
>
>
>
>

There you go. Couple of 15.5 X 1.85 Eather three blades and you're in business!

Go, Doug!

Ted

>>Ohhhhhh, me like 'em 22000 RPMS!!
>>
>>Thanks for the info guys.
>>
>>
>>
>>
>
>There you go. Couple of 15.5 X 1.85 Eather three blades and
>you're in business!
>

You forgot the earplugs!

Brett

Some of these were for Ducted-fan applications also. (rear exhaust)

>>>Ohhhhhh, me like 'em 22000 RPMS!!
>>>
>>>Thanks for the info guys.
>>>
>>>
>>>
>>>
>>
>>There you go. Couple of 15.5 X 1.85 Eather three blades
>and
>>you're in business!
>>
>
> You forgot the earplugs!
>
> Brett


WHAT? WHAT DID YOU SAY?

earplugs?? who needs 'em, we're men....ARRGHH ARRGHH!!!

didnt Randy have a counter rotating assembly? I want to see that thing in action.

funny that you came up with that pitch Brett .
I ended up with a 6x1.8 on my 1/2A cyclon the last time i flew it last year at about 24,000 RPM on 60 foot lines and that was about the right speed.
and yes i do remember the judges commenting on the noise level of that setup as well.

Dave jr.

the nice thing about a rear intake setup is it you can make counter rotating setups out of them pretty easy

>Dave jr.
>
>the nice thing about a rear intake setup is it you can make
>counter rotating setups out of them pretty easy

A few years back I had a counter rotating Nelson 40 rear intake in a Formula 40 speed plane that did 150mph from a standing start. On takeoff, instead of wanting to roll up and to the left (so as to come in at you and eat your face), it tended to roll away from you and stay low (the best speeds are had two feet off the deck). My pilot, Jim Rhoades (who is older than I am, I'm embarrassed to admit, and who held the long-standing record in F-40 at the time), said the counter rotation made the plane very stable and easy to fly.

Speed engines have since morphed back into front intake. I'm told that's because the total contact area between the internal parts, and thus the total overall friction, is less in a front intake. To counter weak crankshafts due to large intake valves, Nelson build a 40 with a 3/4" crank. The early version vibrated so badly that it would crack the pan. Nelson did some work on improving the counterbalance. That was a while ago now.

Kim Mortimore

Doug,

I placed 9th at the '92 Nats with one, and qualified many other times with one.

Take the pylon sleeve out and stick in a VF sleeve and piston. I ran it on a pipe. The timing of the disc valve is a bit more than regular stunt numbers, but it runs. The length of fuel draw is minimized with a rear intake engine. The crankcase is stuffed more than you'll ever accomplish with any stuffer backplate (the volume in the crankshaft is a large percentage of crankcase volume).

I might also mention that I ran it as a front exhaust and inboard cylinder also.

The world champ winner back in the '60's (Joseph Gabi???) used an MVVS .35 that was a copy of a Dooling 29. It was a rear intake engine.

Frank,

I remember that one. Was it the one with the killer looking curly-Q header on it! Nice plane, flew very good too.

I am bummed I am going to miss the new slotted plane this year. Maybe if you score some extra cash you can come to Dallas in the fall and kick or butts with it. I would love to bounce an idea or two off of you that I have for that application.

The 40 VF and the 40 VRP shared a common crankcase, you could drop a VRP liner in the VF and they would go like stink.
One of the big problems of the VRP is the abn coated brass disc pin which were prone to fail real easily if you didn't balance the disc rotor.
I have one of the Stunt MVVS motors, here's a pic. It was based on the racing MVVS 29 that was indeed a copy of the Dooling

[photo not recovered: 29427.jpg]

Attachment #1, (jpg file)

Nice picture ...
It was twin ring I think.

The OS V motors also had a drum rear intake as well as the disk.

I made a rear intake ST60 back in the '80's. Dowell in the crankshaft, an HP 40 backplate and disc assembly, stuffed into the cavity of the regular ST backplate. Ran great for about 12 flights ... rear assembly wasn't firm enough though ...

I had a second hand OS 40 vf that I used a vr-p liner and a homemade left hand crank for carrier. Making crankshafts is a pain. I later reassembled that motor with somewhat stock parts for a stunt project, lost intrest in it and sold it on e-bay.

They make a very good CARRIER engine.
Bill

I have a boatload of these left over from r/c f-1 days. If anyone needs anything for this engine I probably have it many times over. Mike K.