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Author Topic: OS 40 SR FOR STUNT ?  (Read 2148 times)

Offline Robin_Holden

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OS 40 SR FOR STUNT ?
« on: September 12, 2008, 01:26:12 AM »
Greetings from the French countryside........

Just a quickie .

The OS 40 SR in original Stunt form , not converted from R/C.

Any good for stunt ?

Much obliged as ever for any helpful advice guys.

Regards ,

Robin [ ex-pat Brit in the Charente full of ex-pat Brits ! ]
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Offline Just One-eye

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Re: OS 40 SR FOR STUNT ?
« Reply #1 on: September 12, 2008, 03:42:17 AM »
Robin, the only fairly recent CL 40 from OS, other than the FP & LA bushed shaft model engines, is the 40 SF.  TTBOMK, the FSR was never offered without an RC throttle on it.

There have been several threads about the 40 SF, and the next size larger, the 46 SF, in various forums on this site.  I've never even run the one that I have, although I was anticipating having to go high rpm / low pitch to keep the air speed down. 
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Offline Ralph Wenzel (d)

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Re: OS 40 SR FOR STUNT ?
« Reply #2 on: September 12, 2008, 08:25:12 AM »
Actually, the OS .40FSR was available in a C/L version. The only reason I know this is that I purchased one from Lew McFarland around 1980-81 to put in an M&P Stiletto kit. Very strong engine, but definitely not a 4-2-4 type run. My recollection says around 11, 000 rpm on 5% fuel with a TF 12-4 prop.


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Ralph Wenzel
AMA 495785 League City, TX

Offline Balsa Butcher

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Re: OS 40 SR FOR STUNT ?
« Reply #3 on: September 12, 2008, 03:01:11 PM »
.40 FSR: One of the first useable high RPM/low pitch motors.  Similar run to a VF-40.  A flying buddie is currently running one on a profile Cardinal w/a 11 x 4  prop and lotsa RPM.  I have one, haven't run it.  I have heard its weak point is the ring which wears out fairly quickly.  I don't know if there is a difference between the R/C and C/L version - other than the carb.  Worth buying? probably.  Worth putting in an airplane?, your call.
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Pete Cunha
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Offline Mike Greb

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Re: OS 40 SR FOR STUNT ?
« Reply #4 on: September 13, 2008, 06:04:09 AM »
The os40fsr cl came with a crankshaft with milder timing and a head with lower compression.  I had one of these and also a motor that was converted from RC.   I always liked the converted rc better than the control-line version. However the ring fit was so variable in those motors that my CL motor may have had a weak sleeve/piston/ring fit.
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Offline Just One-eye

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Re: OS 40 SR FOR STUNT ?
« Reply #5 on: September 13, 2008, 07:18:14 AM »
There probably were some ABC (actual Chrome, rather than Nickel) FSR 40s twenty years ago, but AFAIK, all of the SF 40s were ABN, and they were available for CL until relatively recently, compared to the FSRs.

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Offline Andrew Hathaway

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Re: OS 40 SR FOR STUNT ?
« Reply #6 on: September 13, 2008, 10:26:59 PM »
The Impact article in Flying Models (5/91) mentioned the 40 FSR... Specifically that the ring was the weakness, and that the fix was to install a 40FP piston/liner in the FSR case. 
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Offline dennis lipsett

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Re: OS 40 SR FOR STUNT ?
« Reply #7 on: September 15, 2008, 10:04:50 AM »
Quote from: Pete Cunha on September 12, 2008, 03:01:11 PM
.40 FSR: One of the first useable high RPM/low pitch motors.  Similar run to a VF-40.  A flying buddie is currently running one on a profile Cardinal w/a 11 x 4  prop and lotsa RPM.  I have one, haven't run it.  I have heard its weak point is the ring which wears out fairly quickly.  I don't know if there is a difference between the R/C and C/L version - other than the carb.  Worth buying? probably.  Worth putting in an airplane?, your call.

I've had quite a few OS40FSR's and still have 3 of them left. That said I was suprised at the comment that the rings wore out quickly. I dug out my oldest one and that was bought soon after their introduction and I ran it for at least 10 years in quite a few R/C ships. This was done with the typical R/C fuels and normal flying. Engine was then converted to a Davis Diesel head and run for a few more years as a diesel with no apparent degradation of performance.I've checked the other 2 that I have and have to say that they are also in very good condition. The only thing that I ever changed on these engines was the bearings.
Dennis
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Offline Balsa Butcher

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Re: OS 40 SR FOR STUNT ?
« Reply #8 on: September 15, 2008, 01:06:47 PM »
Just a quick friendly response to the above: The ring comment was based on discussions with more than one top lever flier regarding this engine.  I never used one in its hey-day and mine will probably remain safely in its box for the forseeable future. Mike and Andrew's comments do seem confirm my assertion that there were ring issues with this engine.  Perhaps it is a matter of inconsistent fit rather than a wear issue.  At any rate, I am glad to here that some have used this engine successfully and if the ring goes bad, Frank Bowman makes replacements and there is always the .40 FP P&L swap.
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Pete Cunha
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Offline Just One-eye

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Re: OS 40 ("F")SR FOR CL
« Reply #9 on: September 16, 2008, 05:33:08 PM »
I ran across a notice of a sale at which the seller used part of the name of the engine the same way and I've eMailed him about it.  He acknowledged the advice, however hasn't made a correction yet.  For what it's worth, I have had the RC version for a long time, myself, and have never gotten a CL venturi for it. 
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Offline Robert Zambelli

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Re: OS 40 SR FOR STUNT ?
« Reply #10 on: September 16, 2008, 08:07:12 PM »
Hey, one-eye.
I'm the seller of the 40 that according to this statement:

"Has no one offered the advice that OS Max did not market ANY engine with the name "SR"? The pictured model engine was named the FSR. You are confusing its name with the "SF" from OS Max that replaced the one you are selling."

does not exist.

When I list an item, I describe it as honestly as possible and if something is cast into the case, I'd say that pretty well sums it up.

Check out the picture. If OS didn't market it, why does it appear as such. AND, the crank is stamperd "S".

Bob Z.

ps - I have plenty more.
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Offline Mike Greb

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Re: OS 40 SR FOR STUNT ?
« Reply #11 on: September 17, 2008, 03:34:29 PM »
The OS max 40 fsr (Front rotor)and 40 rsr (Rear rotor) both used the same case center section.  I have a bag full of OS rsr and fsr crankcases and they are marked 40sr.
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Offline Brian Hampton

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Re: OS 40 SR FOR STUNT ?
« Reply #12 on: September 17, 2008, 10:24:35 PM »
My engine below is the original SR which was the first conventional 2 stroke made by OS after buying the CNC machinery needed to make their Wankel. It was intended only as a RR or Pylon engine and the case was marked with SR. OS then used the same crankcase (and obviously same moulds) for the front intake sport engine commonly known as the FSR. F presumably simply means Front induction.
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