Author Topic: Paul Walker-Tom Lay O,S .35/.40 stunt engine ????? (Read 2908 times)

frank mccune · « **on:** May 04, 2016, 06:24:56 AM »

Hello All:

I have in my collection of old engines an engine that I would like to gain some knowledge of its capability as a stunt engine.

From the paperwork included with the engine it appears to be the following:

A Paul Walker design.

Mr. Lay took an O.S. .35 Stunt engine and fitted a ST .46 piston and sleeve to it to produce a very light.40 engine.

He also took .010" off the piston baffle. The letter included with the engine has operating instructions and is dated 1977.

I have not run this engine as of yet but I may put it into an ARF Nobler or an ARF Oriental.

Does anybody know anything about this engine? How well did they run as a stunt engine? Are they a "strong" engine for stunt use or am I wasting my time with this hybrid?

Any suggestions or comments regarding this engine?

Tia,

Frank McCune

RandySmith · « **Reply #1 on:** May 04, 2016, 09:53:32 AM »

Hi Frank

I did the same many years ago, and they ran very well, except for the trimming the baffle it should be good. the baffles job is to deflect the fuel charge up into the combustion chamber, lowering it only results in less power and more fuel use.
matter of fact they run better and produce more power if the baffle height is increased. ST did this to many of their engines, the COMO 51 ( a very great stunt engine)was a perfect example. and when I made pistons for bored ST 46s the baffles were made taller and worked much better.
Some I even milled down the top back side, this changed the timing and effectively made the baffle taller

Randy

frank mccune · « **Reply #2 on:** May 04, 2016, 01:12:02 PM »

Hi Randy:

Thanks for the reply.

I placed the engine on a test stand after cleaning the mess out of it. After a small prime and a small choke, it started on the first flip. In the instructions, it is sated to use a 10x6 prop and about 28% of CASTOR OIL. I guess that the castor is supposed to protect the bushing and rod better than a blend of oils. This was probably the thinking in 1977. However, things may have changed a bit as many people have changed to a 50-50 oil mix and have not noticed any problems with their engines. For me, I am a bit concerned that all castor oil and a ring may not be the best mix for lubrication. Many of my friends have stopped using all castor in their engines and are happy.

Be well,

Frank McCune

RandySmith · « **Reply #3 on:** May 04, 2016, 02:16:44 PM »

Quote from: frank mccune on May 04, 2016, 01:12:02 PM

Hi Randy:

Thanks for the reply.

I placed the engine on a test stand after cleaning the mess out of it. After a small prime and a small choke, it started on the first flip. In the instructions, it is sated to use a 10x6 prop and about 28% of CASTOR OIL. I guess that the castor is supposed to protect the bushing and rod better than a blend of oils. This was probably the thinking in 1977. However, things may have changed a bit as many people have changed to a 50-50 oil mix and have not noticed any problems with their engines. For me, I am a bit concerned that all castor oil and a ring may not be the best mix for lubrication. Many of my friends have stopped using all castor in their engines and are happy.

Be well,

Frank McCune

I used 28% oil 50% synthetic

Randy

frank mccune · « **Reply #4 on:** May 04, 2016, 04:29:36 PM »

Hi Randy:

A couple of days ago, I mixed up my next gallon of fuel and I too mixed 14% syn,, 14% castor and 10% nitro. I am going to try this for all of my fuel needs. I still keep a bit no nitro fuel available for testing odds and ends.

Be well,

Frank McCune

MikeyPratt · « **Reply #5 on:** May 05, 2016, 06:00:15 PM »

Quote from: frank mccune on May 04, 2016, 04:29:36 PM

Hi Randy:

A couple of days ago, I mixed up my next gallon of fuel and I too mixed 14% syn,, 14% castor and 10% nitro. I am going to try this for all of my fuel needs. I still keep a bit no nitro fuel available for testing odds and ends.

Be well,

Frank McCune

Frank,
That recipe will work just fine. Oh! If you don't want to mess with that lousy, old cranky OS 35/40 just send it to me. I have one that was built by the Tom and it only has about 55 + gallons threw it and still runs like a champ.

Mikey

Air Ministry . · « **Reply #6 on:** May 07, 2016, 02:33:36 AM »

How do you go with these?. Bore out the case & throw the ST top end & rod in??

I see the PC.D./ head bolt paterns / match . Wondering how a B. G. abc set up would turn out in one , the .46 abc .

Any other tecnicalities other than matching the liner to the case ? , suposing it needs a hoop out relief to clear the big end , with the S.T. rod .

gunna check the 35 C case liner bore dia , as this head too is same p.c.d. .

RandySmith · « **Reply #7 on:** May 07, 2016, 09:25:59 AM »

Quote from: Matt Spencer on May 07, 2016, 02:33:36 AM

How do you go with these?. Bore out the case & throw the ST top end & rod in??

I see the PC.D./ head bolt paterns / match . Wondering how a B. G. abc set up would turn out in one , the .46 abc .

Any other tecnicalities other than matching the liner to the case ? , suposing it needs a hoop out relief to clear the big end , with the S.T. rod .

gunna check the 35 C case liner bore dia , as this head too is same p.c.d. .

Hi Matt

you have to bore the case,A early ST 46 with the thin sleeve is preferred, but either will work, , then a light cut across the top to square the case, make a rod, the ST will not fit, the bottom is the wrong size, you could remake and install a new bushing, the ST 40 head has the same bolt pattern, the ST 46 head is a larger diameter pattern, so I used a head insert and a ST 40 or 35 head as a clamp, to hold in the head button. you cant put too much compression or pressure on it because of the tiny case bushing.

Randy

Steve Helmick · « **Reply #8 on:** May 17, 2016, 11:52:00 AM »

Reading this got me to thinking about converting a ST .35 "C" case (stunt or combat version) with a B.G. ST .46 ABC P&L. Not quite as light and compact as the OS .35S, but definitely a sturdier engine. The conversion might be a lot easier, and the results could be better. The plain bearing .35 Combat was a wonderful engine for me, way back when. Never broke one, and often ran 50% "Vitamin N"!

Steve

RandySmith · « **Reply #9 on:** May 17, 2016, 02:58:23 PM »

Quote from: Steve Helmick on May 17, 2016, 11:52:00 AM

Reading this got me to thinking about converting a ST .35 "C" case (stunt or combat version) with a B.G. ST .46 ABC P&L. Not quite as light and compact as the OS .35S, but definitely a sturdier engine. The conversion might be a lot easier, and the results could be better. The plain bearing .35 Combat was a wonderful engine for me, way back when. Never broke one, and often ran 50% "Vitamin N"! Steve

I have 4 of the St 35s I made into 49s and 51s, and 1 bushing 35 that is a 42, makes for great running little engines,
Many people also used the older COMO (Sup Tiger) 40s and 51s to make larger displacement stunt engine, the 40 and 51 is easy to take to 56, and you can take the 51 all the way out to a 74, if you make the parts, you can increase the bore/power with a ST 60 piston sleeve head combo
I have several of these I did back years ago, still run great, matter of fact the COMO 51 is a very very good stunt engine STOCK

Randy

Author Topic: Paul Walker-Tom Lay O,S .35/.40 stunt engine ????? (Read 2908 times)

frank mccune

Paul Walker-Tom Lay O,S .35/.40 stunt engine ?????

RandySmith

Re: Paul Walker-Tom Lay O,S .35/.40 stunt engine ?????

frank mccune

Re: Paul Walker-Tom Lay O,S .35/.40 stunt engine ?????

RandySmith

Re: Paul Walker-Tom Lay O,S .35/.40 stunt engine ?????

frank mccune

Re: Paul Walker-Tom Lay O,S .35/.40 stunt engine ?????

MikeyPratt

Re: Paul Walker-Tom Lay O,S .35/.40 stunt engine ?????

Air Ministry .

Re: Paul Walker-Tom Lay O,S .35/.40 stunt engine ?????

RandySmith

Re: Paul Walker-Tom Lay O,S .35/.40 stunt engine ?????

Steve Helmick

Re: Paul Walker-Tom Lay O,S .35/.40 stunt engine ?????

RandySmith

Re: Paul Walker-Tom Lay O,S .35/.40 stunt engine ?????