gcb

An update on the chronology of the old ST engines:
From the Dec 1968 World Engines advertisement in AAM, The G21/29 and G21/35 were changed to a single ringed piston.
* The plain bearing 35 (combat?) remained the same.
* The plain bearing 35 stunt was changed to a single ring.
* The G15 was new and came in both front and rear induction as a glow or diesel. Also, ST produced a conversion kit to switch from front induction to rear induction.

I also noticed that the G20/15 diesel shown had the longer intake. Mine (1960) has the short intake. Don’t know when they switched.

The G20/15 crankcase was updated in 1970, but I THINK by that time they only used it on the G20/15 glow and the G20/23 glow.

These changes may have been made a little earlier. I just happened to be reading that old magazine.

George

Edit: Oops, the mag was American Aircraft Modeler (AAM), not MAN.

Silvaire

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In digging through my boxes of "junk", I found a few old Super Tigre engines. Looking around trying to figure out what I had, I found this thread regarding G21 engines. I have a G21, but it dose not look anything like the ones you have posted pictures of. Can anyone here tell me anything about this engine? I also found a couple of old Super Tigre diesels, one of which I have also pictured. Rather unconventional looking to me, with the rear rotor and front crankcase split only.

The G21 with the rear rotor looks to be a racing engine? Any info would be appreciated. If it matters to you, both of these will be going "on the block" as they are not really my interest...

Arlen

Strat2003

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I have a rear rotor G21 .29 just like the one in your picture. It was supposedly built in 1972 as a control line speed engine but I bought it (never run!) to use in SAM B Glow. I sent it to Don Blackburn, the SAM engine guru for tuning and he said he'd never seen one just like it as it seems to be one of the earlier ABC engines...most were conventional iron sleeves at that time. Is yours ABC? The large intake means they need to be run on some sort of pressure. Mine uses a presure tap in the upper left backplate bolt hole that runs into the bypass.

It runs real well, in the 18,000's. They seem to be the engine of choice in B Glow and are much sought after on auction sites.

Silvaire

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Strat,

Thanks for the reply. The rear rotor G21 I have dose have an ABC liner. It did look to me like something other than a run of the mill engine, and as it is set up, it would require pressure. As I said in my original post, my heart really isn't in it, and it will be posted "you know where" - probably in the next week or so.

Arlen

mokipitts

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Read your input on the ST 35 stunt.
You dont know where I could find a combat or a stunt ST 35.
Just lost one on ebay I was bidding on, it had large bypass case, was a combat...
Just curious

Thanks

Jim Thomerson

The diesel pictured is a G31 1.5 cc. There should be a rubber cap over the end of the backplate. I had one and though it a very good engine. There was also a similar G29, with red fins, at 1cc, and G30 at 2.5 cc.

Lou Crane

Silvaire,

I'd heard somewhere that the .15 rear rotor was almost an accidental. ST had started to develop a .10 glow, front intake, sport engine, but changed plans. The back end of yours, allegedly, was to have been the front end of the other engine. More of a market for a high performance .15?

BTW, mine has a brass plug in the end of the 'crankshaft' at the back... Amazingly noisy engine, and turns fast. Wouldn't, and didn't, use it much - very scarce, and ST even then had a reputation for scarce parts for even popular engines...

gcb

Mine came without the rubber endcap also. Perhaps someone lost it while handling it in the hobby shop. Didn't affect performance. Still have that engine. Usta have ( [] ) the G30 also. Traded it off back in the day.

George

cfrizell

In one of my very old Aeromodeller or Model Aircraft magazines Peter Chinn was complaining about the Super Tigre numbering system.

The "G" does indeed stand for Garofali and the number, as far as I can recall, is the "series" number which is basically determined the the crank case casting. I STILL find the various G numbers very confusing, but then have only had a couple of Super Tigres; a nice racing 29 RV and one of the fast 15's of the 70's

Charles

ponda

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Does anyone know where one can find some parts for a G-21 .35 ? Been looking , but nothing has turned up so far....
Was trying to re-animate this oldie...used some modern fuel..think it fried the front bearing...if parts are available, will try to re do it...
This was a damn good running engine..thx in advance...

gcb

ponda,

Some parts may be interchangeable with another engine or you might want to have it repaired by an engine guru.

Some ST engines used bearings especially machined for only ST. I would contact Boca Bearings and see if something is available. They used to have a LOT of sizes for model engines, and a well informed staff. I assume that is still true. You may have to disassemble it and supply measurements.

Wow! This thread was started three years ago. Time flies.

George

stg61abc

Hi guys, pictures from my ST "C" 35 Combat running, have fun!!

cutaway

The C35 is a real nice engine. Much less fussy than the G21. Top end isn't quite as fast, but they're not prone to crank breakage or trashing the rear bearing either and they're significantly lighter.

On 40% nitro turning a RevUp 8x8, a stock G21 would be guaranteed to puke the crank eventually and waste the rear bearing, but it would run a tad faster than a Fox 36XBB until it grenade'ed. That speed advantage started vanishing when the first Fox schnurle port combat special appeared circa 76' (the one based on a modified 36X case) and was completely gone by the time the Fox Mk3's and 4's appeared. The early schnurle Foxes had crank breakage issues too. I puked a couple during the runup to the 76 Nats. Duke had people attending the bigger contests handing out revised ones for free. Rick Brasher made some bullet proof cranks for the Mk2 (or maybe it was 3). I got two of those and never had another problem.

There is a standard Fafnir bearing that will replace the rear in the G21. The Fafnir's cage wasn't as prone to disintegration as the stock ST.

ponda

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Good info on here ..Any idea where someone would find a replacement crank for a G-21 .35 these days....and what it might cost?
I have an older engine and think somewhere in its life,the crank was damaged..it feels kinda funky when you turn it over...been looking for one on the Bay, but nothing has made an appearance...Maybe something will wash up one of these days....

It doesn't interchange with any of the other engines , does it,,,someone said some of the parts exchanged with each other....?

Thanks in advance...joe

cutaway

A bit of grit trapped under the external front bearing shield will do this on a G21.

ponda

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You are talking about the kinda shiny part that covers the front part of the nose piece..right? I just replaced both bearings with Boca replacements..was hoping it was a bearing problem..it didnt change anything....

sugodicozze

Hi all,
let's continue this thread in 2008

Who can tell me bearings sizes of G20/15 (.15 ci, 2.5 cc) built in '80s?
Thank you

Antonio