Can anyone offer any experiences or recommendations for using a stock ST G21/40 in stunt? Props, fuel, venturi, etc.?
Thanks in advance!
Thanks in advance!
ST G21/40 Set Up?
Stuka Stunt Main Forum · 13 of 13 known posts recovered
Send it to Tom Lay first and have it re-worked.
Bill Morell
Ontario, California
Better to have it and not need it than it is to need it and not have it!
A great civilization is not conquered from without until it has destroyed itself from within. W. Durant
Ontario, California
Better to have it and not need it than it is to need it and not have it!
A great civilization is not conquered from without until it has destroyed itself from within. W. Durant
My hope was to use it stock without rework. That is why I was looking for experiences others may have had with the engine.
My experience with them was that they were more of a free flight engine. Didn't do a good 4-2-4 break. Had to be run in a wet 2 kinda like ENYA 5224 29's and 35's. It was worth the $ and the time sending it to Tom. Mine is one the rare G 21 40's that has the muffler lugs on the case. Not to many of those were produced as far as I know.
Bill Morell
Ontario, California
Better to have it and not need it than it is to need it and not have it!
A great civilization is not conquered from without until it has destroyed itself from within. W. Durant
Ontario, California
Better to have it and not need it than it is to need it and not have it!
A great civilization is not conquered from without until it has destroyed itself from within. W. Durant
I have a G21 40. It is a strong runner with the stock venturi. It won't run like the G21 46. It needs to run in a slightly rich 2 stroke. Some may need an extra head gasket to soften the run slightly. I like mine.
SAVE ALL THE PIECES-Phil Brown
http://hangarflying.proboards18.com/index.cgi?board=wire
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cwmcmillin · Oct 08, 2011 01:39 AM
#5 sourceHi David,
I have a couple but have only run one of them. It is a Tom Lay version with his venturi and needle valve assy through the middle of the venturi, not the sprinkler type of the stock ST. I always thought they ran well in the wet two cycle run, like Bill and Phil mentioned, with a slightly lower pitched propeller than a typical stunt engine. Mine too has the muffler lugs and I use a tube muffler, 10 to 15% nitro with about 22 to 24% castor/syn blend, and an 11x5 or 10.75x5 or so, propeller.
It feels like a slightly weak, buzzy ST 46. Perfect for some smaller ships like the Sig Chipmunk sized Stunters on down.
Chris...
I have a couple but have only run one of them. It is a Tom Lay version with his venturi and needle valve assy through the middle of the venturi, not the sprinkler type of the stock ST. I always thought they ran well in the wet two cycle run, like Bill and Phil mentioned, with a slightly lower pitched propeller than a typical stunt engine. Mine too has the muffler lugs and I use a tube muffler, 10 to 15% nitro with about 22 to 24% castor/syn blend, and an 11x5 or 10.75x5 or so, propeller.
It feels like a slightly weak, buzzy ST 46. Perfect for some smaller ships like the Sig Chipmunk sized Stunters on down.
Chris...
Chris McMillin
Ditto pretty much what has been said on these. I had a used T&L .40 and another I got from Tom. Both worked ok but its not a .46. Yes you can use them stock but it isn't a stunt engine. Better engine is OS .40H BB. Enya .45 BB #6001. Enya is as good as ST G-21.46. OS .40H runs great and very smooth. The .40 ST were used in Rat Race back then.
Dankar
Luis De Santis · Oct 08, 2011 04:25 PM
#7 sourceI still have an early version of the G21/40 with lapped iron piston and supertigre porting and it always gave runaways because it was not designed for slow stunt. For this engine the best thing for stunt is to run it at relatively high revs with low pitched props to archieve a steady run. Yes, even with ball beraring crankshaft, they work better with more than 20% oil, better 22 1/2 to 25%
Luis
Luis
I have one of these too does anyone know if the 46 strap on muffler will fit a 40 ?thanks T.J.
Indeed . Case is same as 46 , externally . Crankshaft is same part No. In the Ringed version / baffled piston , the trans / ex. timings
a few degree higher than the .46 . Not a lot .
With the weenie stock C/L .40 / .46 intake , and a 11 x 5 master prop
it should behave well . In fact near identical to a .46 if you leave the muffler off .
However the piston is cutaway fore and aft to clear the C Shaft.Were told . So theoritically a slight power loss moffled , as at the corners the case is open @ tdc. So if youre up around 60 Oz , you
might notice it . Biggest venturie I ran on suction was 6 mm bore
with the rear fitting stock spraybar peripheral jet venturie .
Or the little 1/8 in bore 21/35 venturie .
This , on no nitro (or muffler) would swing a 12x6 wood Master prop ,
and suck a bit of juice doing it .Normal prop was the 11 x 5 , 57 Oz plane, with a variety of mufflers . These venturies run smoother with Muffler Pressure . Fitted a 11 x 4 Tornado for howling gales .
Flown it in Over 30 Kt wind . But had practised a little .
Did the pattern , actually .
Likes a bit of a bark in the exhaust ,not to choked .Flew my other
one quite a bit a year back . Testing .11 x 4 Tornado 3 blade & props mentioned.Not the distinct switch , but coming on the power vetically and where required. Nothingll switch overpropped . 60 ft
lines. Used the 67s on the Folkerts , 10 Yrs back . Still got both engines. S/H ex careless types . Can go loose withem rather than
risk a .46 , if ' exploring posibilities ' .
If you really want to suck the juice , fit the 9 mm 21/35 Combat intake & crankcase pressure , Running 20 % nitro and the 11 x 4 , you get maybe three minutes on 150 cc / 6 Oz. of fuel .And it will
take the skin off youre fingers if you turn the prop ,A determined
flick is required , or fit a few head gaskets .
Was advised by a rather experianced flyer hed never seen fuel go down a fuel line that fast , and that the bearings (original in an old S/H ex radio motor ) sounded ' a bit rough ' . So fitted new ones
Good engine for a Mk 2 T-Bird size plane , 10 % nitro would getter
running real smooth and predictable.And Supertigres allways ran high compression. Gives em the snarley exhaust note .
Yea , muffler wise , the 21 cases are the same , across the range .
With the No Lug , and a few variations of lug , other than the Pipe Flange type ( usually 29s ). If the muffler fits a .46 Exhaust , it
should fit the same to the same type of 40 case . same as Merco bolt
pattern on the cases with the muffler bolt holes fore and aft.Most
of the earier ones have got the R/C rotateing Ex. Baffle hole in the
cetre of the stack , so A single bolt will hold a light tounge muffler. Sabotageing the bolt , a few nicks opposite or a cut half
through with a hacksaw , will let it break if you dork it , rather than mangling the case , and leave some to unscrew afterward , if
the cuts out from the case face. For side mounted engines.Half the
time a OS 35 / 40 Max. 703 ? muffler will drop on , particularly if
its a bit old and loose on the OS . Even on the Lug Case.Useing a
longer screw and the OS strap . I bored the outlet 1 mm odd .
21/40s got good authority pulling a 50 Oz plane up the triangle ,
noticeable compared to a old 21/29 swapping them .
11 x 5 wood Zinger , or better , the 12 x 5 cut down to 11 in
a few degree higher than the .46 . Not a lot .
With the weenie stock C/L .40 / .46 intake , and a 11 x 5 master prop
it should behave well . In fact near identical to a .46 if you leave the muffler off .
However the piston is cutaway fore and aft to clear the C Shaft.Were told . So theoritically a slight power loss moffled , as at the corners the case is open @ tdc. So if youre up around 60 Oz , you
might notice it . Biggest venturie I ran on suction was 6 mm bore
with the rear fitting stock spraybar peripheral jet venturie .
Or the little 1/8 in bore 21/35 venturie .
This , on no nitro (or muffler) would swing a 12x6 wood Master prop ,
and suck a bit of juice doing it .Normal prop was the 11 x 5 , 57 Oz plane, with a variety of mufflers . These venturies run smoother with Muffler Pressure . Fitted a 11 x 4 Tornado for howling gales .
Flown it in Over 30 Kt wind . But had practised a little .
Did the pattern , actually .
Likes a bit of a bark in the exhaust ,not to choked .Flew my other
one quite a bit a year back . Testing .11 x 4 Tornado 3 blade & props mentioned.Not the distinct switch , but coming on the power vetically and where required. Nothingll switch overpropped . 60 ft
lines. Used the 67s on the Folkerts , 10 Yrs back . Still got both engines. S/H ex careless types . Can go loose withem rather than
risk a .46 , if ' exploring posibilities ' .
If you really want to suck the juice , fit the 9 mm 21/35 Combat intake & crankcase pressure , Running 20 % nitro and the 11 x 4 , you get maybe three minutes on 150 cc / 6 Oz. of fuel .And it will
take the skin off youre fingers if you turn the prop ,A determined
flick is required , or fit a few head gaskets .
Was advised by a rather experianced flyer hed never seen fuel go down a fuel line that fast , and that the bearings (original in an old S/H ex radio motor ) sounded ' a bit rough ' . So fitted new ones
Good engine for a Mk 2 T-Bird size plane , 10 % nitro would getter
running real smooth and predictable.And Supertigres allways ran high compression. Gives em the snarley exhaust note .
Yea , muffler wise , the 21 cases are the same , across the range .
With the No Lug , and a few variations of lug , other than the Pipe Flange type ( usually 29s ). If the muffler fits a .46 Exhaust , it
should fit the same to the same type of 40 case . same as Merco bolt
pattern on the cases with the muffler bolt holes fore and aft.Most
of the earier ones have got the R/C rotateing Ex. Baffle hole in the
cetre of the stack , so A single bolt will hold a light tounge muffler. Sabotageing the bolt , a few nicks opposite or a cut half
through with a hacksaw , will let it break if you dork it , rather than mangling the case , and leave some to unscrew afterward , if
the cuts out from the case face. For side mounted engines.Half the
time a OS 35 / 40 Max. 703 ? muffler will drop on , particularly if
its a bit old and loose on the OS . Even on the Lug Case.Useing a
longer screw and the OS strap . I bored the outlet 1 mm odd .
21/40s got good authority pulling a 50 Oz plane up the triangle ,
noticeable compared to a old 21/29 swapping them .
11 x 5 wood Zinger , or better , the 12 x 5 cut down to 11 in
ANACHRONOUS
GWassenaar · Oct 10, 2011 02:52 AM
#11 sourceContrary to the .46, the .40 has so called sub piston induction.
With the piston in TDC , you can see the exhaust open underneath the piston. The could or would imply that the exhaust back pressure
has an influence on the scavenging process. That backpressure may varied by the use of different mufflers.
I run two ST .40 engines and after new rings ( by Frank Bowman!) and a check of the cylinder roundness, they behave just as described above in this thread . Typically for old ST engines, I think one should use 25% pure castor oil. There are no runaways then.
With the piston in TDC , you can see the exhaust open underneath the piston. The could or would imply that the exhaust back pressure
has an influence on the scavenging process. That backpressure may varied by the use of different mufflers.
I run two ST .40 engines and after new rings ( by Frank Bowman!) and a check of the cylinder roundness, they behave just as described above in this thread . Typically for old ST engines, I think one should use 25% pure castor oil. There are no runaways then.
Gerben Wassenaar
quote< If the muffler fits a .46 Exhaust , it should fit the same to the same type of 40 case . same as Merco bolt pattern on the cases with the muffler bolt holes fore and aft.>quote
Not quite same as Merco. Be a bit wary about this. Can be persuaded to fit with a little careful filing to help the holes line up.
Not quite same as Merco. Be a bit wary about this. Can be persuaded to fit with a little careful filing to help the holes line up.
Ian R.