Speed,Combat,Scale,Racing > Combat
ST G21 on suction
dave siegler:
Forgive me, I only had foxes as a kid. I was gifted 2 St G21's ball bearing and want to run one of them on suction. The Choke area is huge (3/8 ") and they don't draw fuel. The location of the spray bar makes is difficult to choke it down with an insert.
How did you do it back in the day? It The back plate is tapped for pressure, but I'd rather not go that route.
Paul Smith:
Those G21's came with a suction venturi of about .125" diameter. It had a sprinkler ring designed to work with rear venturi. There were, maybe 6 or 8 little sprinkler holes around the circumference. They worked very well.
I think your could make a nylon or aluminum venturi with just one hole going back to the spray hole and it would probably work.
dave siegler:
--- Quote from: Motorman on October 13, 2020, 01:43:27 PM ---Are you going to fly a combat job on suction? Do either of the engines have MK2 on the mounting lug?
Motorman 8)
--- End quote ---
Do not see MK2 on lugs. Was given several old slow airplanes (mongoose 1, 2, and spiders) set up with hard tanks and drilled for ST 35's. I want to use them up.
Paul, thanks I make a reducer. .25
dave siegler:
--- Quote from: Motorman on October 13, 2020, 11:18:37 PM ---You'll have to go smaller than .250. If memory serves .1875" max and that's a nicely made perifrial jet venturi.
I might have what you need in my SuperTigre stuff.
Motorman 8)
--- End quote ---
let me know what you need to get for it.
Paul Smith:
I just now measured a couple of them. The factory size is .157". I bored one out and later had to plug it down to make in run.
In the early 1960's FAST was the only kind of combat and nobody had any need for suction. Then our local rules forbad ball bearings and flat top pistons in Slow. So the use of G21's and C's in slow was not possible. That was the day of the Greenhead and the Enya.
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