Numbers for ST G21/35 DDD head
 

Hi Gang:

I checked my ST G21/35 with a DDD head and it turned:

8,500 rpm with the same MAS 12x6

11,500 rpm with a MAS 10x6

How do these numbers compare with other engines? Good of bad?

Oh yes, I did have the the engine leaned out and the compression set correctly.

I am now going to check my tach.

Stay well,

Franchi

RE: Numbers for ST G21/35 DDD head
 

If that is ST .35?? good numbers must be an oldie if its a .35 martin

RE: Numbers for ST G21/35 DDD head
 

Hi AMB:

No it is not the ST.35. I think that the ST .35 was a plain bearing engine that came in a baffled and a flat topped piston model. Later ones had PDP added. One for stunt and one for Slow Combat. They had a C on the case.

The one that I am running is a ball bearing engine that was known as the ST G21-35. It is a .35 disp. engine. Yes, it is quite old. Like all ST engines, I find them to be great engines!

Stay well.

Franchi

RE: Numbers for ST G21/35 DDD head
 

The numbers are correct for a Super Tiger .35. As a Glow .35 the correct prop is a 9X6 , not a 10x6.

RE: Numbers for ST G21/35 DDD head
 

Franchi awsome power as diesel , and thats just one of the diesel advantages martin

RE: Numbers for ST G21/35 DDD head
 

Franchi, this is my G21-.46, it would make great Diesel but it has a baffled piston. It has tremendous compression for ringed engine. Originally it had a butterfly over the exhaust port that was linked to the throttle but Swing Muffler fit perfectly.

RE: Numbers for ST G21/35 DDD head
 

My Russian G20/29 copy, the KOMETA MD5 (5 ccm).

It runs, but leaks combustion gasses badly from blow-by past it's loose (I suspect out-of-round) contra-piston.

I will arrange for one of the talented gents here in Australia to make a new contra-piston for it.

RE: Numbers for ST G21/35 DDD head
 

FIERY nice to have the connections to get your finds in A 1 shape martin

RE: Numbers for ST G21/35 DDD head
 

Yes, very fortunate.

The silencer adaptor sold by MECOA for the ST equivalent engine fits perfectly. So, when I ran it I fitted up the adaptor and a spare KAVAN 'strap-on" silencer. Worked a treat.

Despite its 'Soviet' industrial grade finish my KOMETA is suprisingly well made (apart for the contra issue). No fuel leakage it the front ball race despite the race being 'open'. There is no shield on the prop driver. The gap between the race and the back of the prop driver is substantial. I suspect race life will be short due to dirt ingestion. I may exchange it for a sealed race when sorting the contra. I expect the race is a standard metric size.

RE: Numbers for ST G21/35 DDD head
 

Hello All:

The horsepower numbers that I got with the ST G-21/35 with the DDD head produced the following:

12x 6 prop at 8500 rpm= .519 hp.

10x6 prop at 11500 rpm= .619 hp.

As a side note, the OS .40 engines with the DDD head produced .432 hp with the 12x 6 prop at 8,000 rpm.

One frame of reference that I have always used to evaluate engine performance is the Fox .35 Stunt. It seemed to produce about .45-.50 hp.

If I get some nice weather, I may continue my tests of the glow vs. the Diesel with smaller props.

An expert engine builder who made both glow and Diesel engines claimed the a Diesel will produce as much power as a glow engine on 10% fuel. Of course more nitro would increase the glow engine's power to a higher peak.


Be well,

Franchi

RE: Numbers for ST G21/35 DDD head
 

He must be comparing the glow engine under the same conditions as the diesel, try running a dedicated glow at the rpm that suits it against a dedicated diesel.

And then look at tuned pipes.

Sorry to be harsh here but I find the above quote very disposable and I like diesels.

RE: Numbers for ST G21/35 DDD head
 

That, (quoted) guy needed to qualify his answer, the paper HP produced by both may be the same but thye flying power with the proper prop will be about 50% more with the Diesel. The same goes for four strokes, they produce more flying power than people give them credit for. Both Diesel and fourstrokes produce power more efficiently.

RE: Numbers for ST G21/35 DDD head
 

Bob Davis made the statement years ago " benchs do not fly" martin

RE: Numbers for ST G21/35 DDD head
 

I believe, from an impeccable source, that the quote came from Henry Nelson, a man who produced very high quality, very high performance glow and diesels based on the same components for decades.

It is also backed up by evidence from running glow and diesel versions of the latest Fora Pioneer and Parra 15 engines.

These were designed as diesels but run just as happily (all other things such as venturi hole size and props being equal) as glows on 10% nitro.

This equivalence can be demonstrated I believe either on the bench or in the air.

There is a lot of hyped up nonsense out about diesel conversions swinging bigger props and having 30% more power etc but I believe that it can't be really demonstrated.

It's wishful thinking folks!

:D

RE: Numbers for ST G21/35 DDD head
 

G'Day Gazimoto et. al.:

I lost a long reply so I will post a short reply.

The Diesel will not produce more power that the Glow engine. If this were true, I would have flown combat Goodyear, Rat etc. with a Diesel! It has been suggested that I should be using a 9X6 prop on a ST G21/35. The same person suggested that I should use a 13X4, 12X5 or an 11X6 on an O.S. .40 converted to Diesel. Which do you think would have more speed or power?.

Back in the day, I used a ST G 20/15 Diesel in Goodyear just for fun. The winner used a ST G 15 Glow! Both engines were stock! He was much faster than I! So much for using a Diesel in Goodyear! Lol

Let's see. Diesel fuel $60.00 per gallon vs. Glow at $15.00 per gallon! No brainer for me!

In any case, use what makes you happy but do not confuse facts with fiction!

Stay well,

Franchi

RE: Numbers for ST G21/35 DDD head
 

I ran a glow K&B 4011 on glow with 10% nitro, and then on diesel. I kept the glow plug lit until it was warmed up and running nicely. In both cases it turned an APC 11 x 5 at 9,700 RPM. It had a venturi and ST NVA. I turned the needle in 1 1/2 turns to get best RPM with diesel. I ran a Drone with a MAS 11 x 9 at 6,700 RPM. Put a Drone glow head on and ran it on 10%. It ran smoother at 6,700 RPM. I actually had to turn the needle in a little to get best glow RPM. I understand that is an idiosyncrasy of Drones.

So there!

RE: Numbers for ST G21/35 DDD head
 

GAZIMOTO When you get a chance go to the Davis diesel site and check the reviews part, Ridgeway and Pinnock did several., the MVVS 21,40,49, and OS 40LA looks like a power increase to me the real surprise is the OS LA40 which is a little weak on glow but really cranks out the power as a diesel conversion
There may be a few exceptions, the one that comes to mind is the TT07 which was not too swift on as glow and not much better as a conversion , in fact Davis pulled the head from production on this one, he only goes with the winners best regards martin

RE: Numbers for ST G21/35 DDD head
 

I will use my Fox .74 conversion as an example, it turns a 12x8 Graupner at 11,000 rpm on 5% glow fuel with 20% castor, on Davis Diesel ABC mix it turns a 12x8 3 blade Graupner at 9,500. As a Diesel it flies a GoldBerg 60 at half throttle as well as the glow does at full throttle. That's no BS and it works for me. My SuperTigre .51 turns a 12x6 two blade at 10,500 on 5% glow and a 12x6 three at 10,400 as a Diesel. I have lots of hours on the SuperTigre .51 as a Diesel. Many on a USAircore KnightHawk and a few on a Kombat Copter. It will probably be on a USAircore Colt 40 by summer.

RE: Numbers for ST G21/35 DDD head
 

Hi Jim:

Is your K&B .40 a baffled engine? If so, how much trouble was it to convert it to Diesel?

There is a racing event where the K&B 4011 is the top dog! It may be the 8011 but the one with the larger front bearing is the one that is prefered. The speeds in this event are fantastic. I have not heard of any Diesel engine that can compete with the K&B engines in this event.

Stay well,

Franchi

RE: Numbers for ST G21/35 DDD head
 

As usual with this kind of discussion, that of 'power' everyone ignores the elephant in the room.

The tuned exhaust system. The bane a diesel, the savior to a glow.

Martin, almost the entire MVVS glow range is designed to work best using a tuned exhaust system and yet those old testimonials never use or mention them - strange that.
Want a true 30% power increase? Then try using a mini pipe equipped MVVS glow against a similar diesel.

The cost, MVVS usually don't come with any form of muffler so there is no real loss when choosing a pipe over a canister muffler but lets say that you have any existing engine with a standard canister muffler and want to increase power.
$60US will get you either a diesel head or an MVVS mini pipe - which do you think will give you more 'power?'

I have Dar Zeelons old MVVS 49 converted diesel and even he knows that it will not out perform the same engine as a glow on a pipe.
A search here will reveal that originally he thought that the diesel won out and that's what he 'wanted' to believe at the time but upon a second checking of the figures both configurations using  standard canister exhaust system proved to have about the same amount of power.
Add the pipe and its a no brainer really.

And I dare say that an OS Max 40 with the cost of  conversion head thrown instead at a tuned exhaust system would out perform a diesel - the sticking point here how you want to run the engine, power bands and emotions and I am not saying that one is better than the other.

Cheers.

RE: Numbers for ST G21/35 DDD head
 

The K&B 4011 has a baffle piston, as do all the K&B 40s. The metric elephant engines are all ABC and Schnuerle ported. I ran the 5.8 (= 35) a lot in control line slow rat. At the moment there is Quickie Rat, which is dominated by the 4011. There are various rules to keep things simple, and the venturi size is restricted when speeds get up to 110 MPH, I think it is.