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General control line discussion => Open Forum => Topic started by: David M Johnson on January 19, 2012, 04:57:36 PM
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Are these good stunt motors? are they comparable to the newer OS 35FPs
David Johnson
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They were the gold standard in the early to mid 70's for 35 sized airplanes.
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These are great stunt engines when they are fresh. They do require 29% Castor for lubrication and cooling. 11/11 will burn them up. Ask me how I know. I was in Vietnam in 1968 and visited a hobby shop at Bein Hoa AF base. I purchased one of these S models and a Mk 111 for $10 each. I wished I had of bought both of the S models. The Mk 111 turned out to be junk. I wore the S model out in the 70s. It was the only .35 size engine I had left in the late 90s to fly stunt with. I finally gave it, along with the Mk 111, and a H model, away to a friend of mine. I use mostly FPs and LAs now. Plus a couple of other brands. If your S model has some wear then be sure to use some nitro and lots of oil.
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Are these good stunt motors? are they comparable to the newer OS 35FPs
David Johnson
Good stunt engines for smaller classic type plane (Nobler size etc.). They do not compare to the power available from a OS FP35.
Our host Leonard has modified FP35s that easily turn 12 inch props or larger.
They are several ounces lighter than the FPs however!
Randy Cuberly.
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I have used one for years in my classic plane , Skydancer , , good reliable power , less than FP35, but more of a Fox 35 style run than the fp , .275 venturi, st nva, Big Art Tube muffler .
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I just got one of those in excellent shape but I am concern about it. I read that the conrod is made of a very soft aluminum an needs to be replaced and also needs Teflon pads for the piston pin, if not it will scratch the liner. Can any one point me out where I can get these parts?
Martin
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I know for a fact that an OS 35S was the power for the Walker Cup winner in 1970 on a 610 sq in design.
They like all castor oil, like 28%. The connecting rod will wear out after several hundred flights because the rod is not bushed on either end.
Leonard Neumann has sold from time-to-time replacement rods, some of them I think were bushed.
If you have a new engine that has not been run and you are serious about running it as a serious stunt engine for good performance and life, recommend sending it to Tom Lay to do his magic on it.
Keith
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I know for a fact that an OS 35S was the power for the Walker Cup winner in 1970 on a 610 sq in design.
They like all castor oil, like 28%. The connecting rod will wear out after several hundred flights because the rod is not bushed on either end.
Leonard Neumann has sold from time-to-time replacement rods, some of them I think were bushed.
If you have a new engine that has not been run and you are serious about running it as a serious stunt engine for good performance and life, recommend sending it to Tom Lay to do his magic on it.
Keith
I think I read somewhere that ST G21 .35 rods were interchanble with slight mods. anyone know for sure if this is true?
Randy C.
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I think I read somewhere that ST G21 .35 rods were interchanble with slight mods. anyone know for sure if this is true?
Randy C.
There's a post by Randy Smith in this thread about the ST rods. http://stunthanger.com/smf/index.php?topic=13352
It's a bit of a moot point anyway, since where are you going to find 30 year old ST rods?
I've got a bunch of Max-S 35s. I like them because they generate more power than a Fox 35, and they don't run away like the FPs. The one I've been running on my Nobler has a Bristunt ABC setup (piston, cylinder sleeve, bushed rod, & modern wrist pin). It fixed all the weak parts of the engine, and turned it into a really sweet engine. It turns a wide blade 11x6 prop, runs on modern fuel, and carries a 48oz Nobler with ease.
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Originally somewhere in the early 70s when slow combat went to bushed engines(stupid) I ran the O.S. .35s and had very good but short lived engines.
If it was put in the ground not hard enough to break the airplane with the engine hot the case would warp.
Several flights later would find that the rear wrist pin hole in the piston would be badly worn with the front one and
both end of the rods failing. This indicated the top of the cylinder had moved foward direction and no longer
90deg to crank.
I recently was told by someone who had checked later new cases than I used that the factory had started pre bending the case for us. Recently may have confirmed this upon disassemble a low time pro built engine that was claimed to have never hit the ground. reason for diassembly was that after less than 1 gallon of fuel the engine 'went away'. the drag of the miss alignment could be felt as well.
Plan to chuck this one in the 2 axis Lath/Mill and attempt to straighten it. If successful will receive new 'guts'.
Other problems.
The wrist pin dia is to small for long life.
I have a pile of new rods/pins for the O.S. and for the S.T. engines so next time I build some will look at possibly reaming O.S. piston to use the S.T. wrist pin and Rod or bush the O.S. parts..what ever makes the most sense.
Have enough P&L, cranks rods screws gaskets to build about 6-8 more new engines(O.S.& S.T.) but ran out of cases,heads,backplates for the O.S. HB~>
Thicker thrust washers. Would have to look but I think AN in various thickness is what was used for end thrust on the crank.
29%+ castor helps lots!
The 6 or so of these that I assembled from pre 1975 stock are all nice runners. like a Fox .35 with 50% more H.P.
I like the after marked Bristunt ABC P&L set up idea for longer life and possibly above mods with oil grooved piston to help the P&L life of stock unit.
While on the rod subject the S.T.G-21( and C).35 big end bush is same as S.T.G-21 .60 small end.
Easy swap over. Horrible to have to cut up new S.T. parts for a bushing! HB~> HB~>
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Owner of above said engine has informed me that this engine did make it from the top of circle to ground not running and by taking the shortest route.
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So Gravity works then LOL
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Nah
Didn't even break a sweat. but it usually wins by sucking.
The Nobler survived this attack of gravity, the O.S. did not.
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Good stunt engines for smaller classic type plane (Nobler size etc.). They do not compare to the power available from a OS FP35.
Our host Leonard has modified FP35s that easily turn 12 inch props or larger.
They are several ounces lighter than the FPs however!
Randy Cuberly.
Hi Randy,
I think that "Leonard" would be in shock to find out he was the "host" here............ LL~ LL~
BIG Bear
RNMM/AMM
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Email this morning on the last O.S. .35s I built.
Superb running on Vector .40... Wing fold....warped/bent case.....
If this keeps happening the molded F7F project may be ended.
Looks like I better jig up to straighten cases and figure out how to stiffen them.
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Email this morning on the last O.S. .35s I built.
Superb running on Vector .40... Wing fold....warped/bent case.....
If this keeps happening the molded F7F project may be ended.
Looks like I better jig up to straighten cases and figure out how to stiffen them.
It will be much easier to just stop having those sudden stops to flights......... just sayin'.
BIG Bear
RNMM/AMM
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Alternative is to fly on a muddy field. LL~ LL~ LL~
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It will be much easier to just stop having those sudden stops to flights......... just sayin'.
BIG Bear
RNMM/AMM
Since I stopped flying combat in 75 thats no longer a problem for me....as posted above others are having problems.
Brodak did replace the defective ARF Vector that folded the wing is my understanding.
Engine guts went in an ebay case and running excellent again.
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Since I stopped flying combat in 75 thats no longer a problem for me....as posted above others are having problems.
Brodak did replace the defective ARF Vector that folded the wing is my understanding.
Engine guts went in an ebay case and running excellent again.
OK, OK, but yu forgot to say the Vector was someone else's............ LL~ LL~ LL~
BIG Bear
RNMM/AMM
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OK, OK, but yu forgot to say the Vector was someone else's............ LL~ LL~ LL~
BIG Bear
RNMM/AMM
Shoot Bill, if I could remember what was forgot and forget what I remember the ratio of remembering would multiply exponentially. Might even get the trash out on time if that happened. Would save some of the
mw~ mw~ HB~> HB~> that goes on around here.
My self over last 25 or so years have only had a few R/C landing prangs 2, mind blow what the heck was that insanity(splat) that was the result of accidentally switching helicopter mixing on TX. Switches were superglued and levers cut off after 2nd set of air to ground spasms.
C/L has been good to me this time around with 2 minor prangs with out damage to either O.S. and there was a tree limb involved in another. Tree is now laying dead 50ft away from its home.
oh, Forgot about the full throttle landing on wing over exit with Stubblefields Ringmaster last year.
Flying in 35+ mph gusty winds were blowing the ground up and down. a No bouncer with broke prop and bent gear.
H^^