OS.max puzzle
 

HI ALL,
I need a participation in making a decision, between two brand new engines
Of the 80’s------OS.max 61 VF-------AND of the 90’s---OS.max 50 SX
Power output----1.8HP (17000 rpm)--------------------1.8HP (17000 rpm)
Prop size--------1X7------11X8------------------------11X7.7-----11X8
Weight-----------18.6 oz.------------------------------13.76 oz.
(The above data given by os.)

Now which one works better for a sport model 70 in wing span
(24 oz./sq.ft) wing loading, btw (both engines set ok. In the model)
If some one had actual tachometer. Reading for any of these engines, let us see it

RE: OS.max puzzle
 

go 80's and put in your 70'' model the .61 vf, if you want god performances the weihgt should no exceed 3kg

RE: OS.max puzzle
 

Hi!
The OS VF .61!
Nothing beats cubic inches! That simple.

Regards!
Jan K
Sweden

RE: OS.max puzzle
 

Like Jan says,

You cannot go by published HP figures anyway. They are almost meaningless. I suppose you will be running your engine at 17,000? The engine with the larger displacement will come out ahead up in the air.

At a normal rpm, the larger engine will have more power.

Enjoy,

Jim

RE: OS.max puzzle
 

The biggest difference betweeen the two is the VF is rear exhaust which means that it will be mounted different on the plane. If you have a tuned pipe on hand then the VF will give you great performance. With a Macs muffled tuned pipe (NOT a silent pipe) you could get upwards of 15,000rpm with an 11x7 prop. There's no way a stock 50SX will ever turn an 11x7 that fast.

RE: OS.max puzzle
 

The VF's were probably the best engine OS ever produced....and you've found a NEW one?? As others have said, forget about the stated HP figures, they're worthless. That weight for the 50SX is without a muffler. Although it's not necessary to use a tuned pipe you'll certainly get a big boost in power if you do. I've only had experience with the 40VF but it's one gutsy little engine, with or without a pipe.

RE: OS.max puzzle
 

IRAQ,


This engine has a separate front crankcase, I believe, making it essentially a rear-exhaust derivative of the .61FSR.

This should mean the ABC is really an ABC. Not an ABN titled as an ABC, as most SF engines and their derivatives were.

I guess you have a unanimous recommendation to get the .61VF and to pass the newer .50FX.
I guess that says it all.

The FSR and its derivatives are where OS of today still get much of their good name from.

RE: OS.max puzzle
 

There are tach measurements for both engines in the "Tachometer Readings" forum next to this forum.

RE: OS.max puzzle
 

hi jack,
i didn't fined a reading for the max 61 vf
could you Fwd some think

RE: OS.max puzzle
 

I can't say for certain about the 61VF because I've never even seen one but the 40VF is ABN. My SR and FSR 40's are both ringed so I can't check the later liners. However, I've never heard of any peeling problems with the VF liner.

RE: OS.max puzzle
 

That's right, later versions of the VF series were nickel plated.

RE: OS.max puzzle
 

I've got two VF .61s, both acquired NIB. Inspection of the liner has revealed that they are both ABN. I also have a .46 VF, which appears to be a genuine ABC engine.

I couldn't resist starting one of the VF .61s, so I mounted it in a test stand and broke it in using typical ABC/ABN procedures. It has the best idle and transition of any engine I own at the moment and it tached (with a Macs .60 pipe) at 14,200 with an APC 11x7.

In summary: A very strong performing .61 with impeccable manners.