Author Topic: ST/47 ?? (Read 3027 times)

EddyR · « **on:** December 19, 2016, 06:03:46 PM »

Did any one ever put a st/40 crank in a ST/46 motor. The 46 crank is .7795 and the 40 crank is .7874 I am in the process of moving my original ST46 ABC over to a case with ears on it so I am building some new 46's from parts. I have a few sets of sleeves and pistons with rings. I also have some new ST/40 that have never been run. They have the old style cranks in them which I prefer. If I do this it will move the piston up but that is not a problem as I use to drop the sleeve when I built custom ST/46 motors. Also it is easy to shim the sleeve up if needed.
It will give me a .47+ size. The reason for this is not the increase in size but to use the old style 40 crank which is easier to balance. I have enough parts to build five thick sleeve 46 motors.
Has anyone done this.

EddyR

RandySmith · « **Reply #1 on:** December 19, 2016, 08:07:13 PM »

they take the same crank, Both the G21 40 and 46 use the exact same crank, yes there were some that had less stroke, but no 46 only crank
Thus the reason you see some G21-40s with less sub port and others with more sub port
ST made about 4 different cranks for the G21 40 and 46

Randy

Brett Buck · « **Reply #2 on:** December 20, 2016, 09:53:29 AM »

Quote from: RandySmith on December 19, 2016, 08:07:13 PM

they take the same crank, Both the G21 40 and 46 use the exact same crank, yes there were some that had less stroke, but no 46 only crank
Thus the reason you see some G21-40s with less sub port and others with more sub port
ST made about 4 different cranks for the G21 40 and 46

That was another frustrating aspect of trying to run the ST46, there were endless variations in the parts, with no real way of telling which is which. No two I had were ever quite alike, and they didn't run the same.

Brett

RandySmith · « **Reply #3 on:** December 20, 2016, 10:35:40 AM »

Not only the crank, but there was at least 4 rods, some short some long, at least 3 pistons, 4 heads, 4 different sleeves and at least 4 different heads and many different cases for the ST46, double ring, single ring, thin sleeve thick sleeve etc..
Way back they used a restrictor type venturie, with the case milled across to accept it.
The engine was basically a bored/stroked 29. Then morphed into the later model 46s with bigger beefy er.... case, thick sleeve, a larger stronger rod , hemi hi compression squish band head etc...

you could make all the versions run well, but the last series was the best, what frustrated many, and confused many , as Brett alluded to above, was the large amount of parts, that may or may not work well with each other, and if you did not have all the same model/date parts the engine simply did not fit together.

by the way, the ST 60 is the same way with a huge number of parts, that do not fit other ST60s

Randy

EddyR · « **Reply #4 on:** December 20, 2016, 02:42:32 PM »

Randy and Brett
Yes I am familiar with all the versions of the ST/40,46. I use to order parts from ITALY and I had to be precise. They sent me drawings with all the dimensions on them so I could get the correct parts. I stopped working on them in 1990 as parts began to get hard to get. I continued to work on only late model 46's after that date.
I was looking at the Pete Chinn review of the 40 and saw the .7874 stroke. I had never seen this number befor that is the reason I asked the question. I also thought that 40,46 motors used the same crank. I just measured six cranks and they are NOT all the same stroke. Here is what I found.
   #0075 is used in 46 .7795 stroke
   #AA 40/1 is used in both 40,46 .7795 stroke
   #2010075 is in one of my 46 motors and measures .7900 stroke
All the above had stock sleeves in them and deck height varied so the sleeve ring at the top must very in thickness. I did not measure them.I have six sleeves in a box and measured them and they were all different.

The #2010075 is in one of my old ringed 46 I have not run in many years. I measured it four times as I did not believe what I was getting.
All the 46 motors are thick sleeve motors
Two motors are stock never taken apart 40's with the old style AA 40/1 cranks in them
One crank with no number on it is 3.200" long rather than the more normal 2.920" It is a .7795 stroke

Pete Chinn reviews are of very early 40 thin sleeve double ring motors.
Ed

Air Ministry . · « **Reply #5 on:** December 20, 2016, 06:26:50 PM »

8 thou in it , with his dimesions . more or less .

Air Ministry . · « **Reply #6 on:** December 20, 2016, 06:30:19 PM »

http://vcconline.go-forum.net/t1487-al-rabe-mustang

The Ukrainian chap undoubtedly could do 51 stroker . 46 cranks. And Rods .

a certain chap ( Al Rabe ) stroked one to .51 alledgedly .

offset ground crankpin ?? Definately Offset Bushed big end. in That photo .

( one could of course ' press in ' a big end , as per K&B . if they got it right . Kwacker Sikis they welded big ends on the KRs , Sweated In ? )

When is a 21/26 not a 21/46 / When its a Stalker probably . Maybe a 51 RE would be better . Or at least investigating .
To See How they Did It . If one were going to go to any expense - Presume its a development of their ST 46 Super tigre
copy er development um evolution . If they wernt 1/2 longer in the front, maybe theyd fit .
Likely would bushed @ the front bearing. $:-\$ and available as a spare , via Stalker .

The G15/19 CAR had the same bush set up as the 20/23 in the 2x B R case , so not exactly breaking new ground .

Brett Buck · « **Reply #7 on:** December 25, 2016, 04:37:55 PM »

Quote from: RandySmith on December 20, 2016, 10:35:40 AM

you could make all the versions run well, but the last series was the best, what frustrated many, and confused many , as Brett alluded to above, was the large amount of parts, that may or may not work well with each other, and if you did not have all the same model/date parts the engine simply did not fit together.

I never got to the point of comparing the versions to each other. The later versions may have been the best design-wise but *any* of the 80's versions I got had bad rings, and all the replacement rings from the factory were bad, too. So it was pretty much impossible for me to tell the difference in the design. The very best individual I ever had was essentially the same as the last few batches, near as I could tell, but I think it was made in the early-mid 70's, and came in the red box instead of the blue/white box. It might have been the first muffler-lug version, single ring, porkchop crank, had the long intake, and the (relatively) thick liner. It has the older material ring that took a bit of running to get right, but lasts very well and has great compression in both directions.

The mere fact that it took that long to describe illustrates the issue. About 2 seconds after we found an ABC subsititute (40VF) I was done with ST46s. The fact that it perfomed fantastically better was just a bonus. Even it worked exactly the same, it would have been worth it to avoid the fiddling. Guys today have no idea how well they have it.

Brett

EddyR · « **Reply #8 on:** December 26, 2016, 12:22:34 PM »

Brett Yes they were troublesome for many people. One thing that contributed to the ring wearing out fast was using 12/6 props in large heavy planes. Flyers thought they needed 700 sq" to fly the pattern. The ST/60 soon took over in the same planes the the 46 had been flying. I never built thase large models except one USA/1. I was using smaller 600 SQ" models and 11/5 Props and rings supplied by Frank and ring failure went away. I also went to new sleeves on all rebuilds. This gave me motors that would go 800 runs. When Brian Gardner mentioned the possibility of a ABC set for the 46 I called him the next day and soon I had the first ones in a model. Those early ones needed the wrist pin bosses opened up for better rod clearance. I recommended the hemi head for a smoother 2/4 run. My two prototypes are still running strong after all these years.
When talk about the ABC setup for the 35 came up I sent him of my 35's to measure.
I had been doing reworks on the ST/35 since the one piece case came out. There were many versions of this motor also There was a seldom seen ringed version that was sold for RC use. I was building slow combat non ball bearing motors with the big ports sleeves before they were available from the importer. I did not even know about the 46 till it had been out several years as I had not entered a stunt contest in many years. One day I was in the hobby shop in Clearwater Fl and saw five used 46's laying on the counter. I bought them and went home and test ran them. I put the best one in a Gieseke Nobler and that started me on several years of the ST/46 saga that you have explained well. I told BoB Gieseke about my Nobler with the 46 in it and he wanted one. I drilled the case low for a one inch tank and set it to him with a drawing of a sump for his built in tank.
Long story but I thought you would find it interesting.
EddyR