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Engine basics => Engine set up tips => Topic started by: Timothy Payne on September 18, 2013, 12:15:20 AM
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Hi everyone out there in the US!
Are we having some bad weather over here right now, (still it gives me chance to perfect my limited modelling skills).
I can also get the engines sorted as well. - Can anybody tell me the correct length of the 4 UNC headbolts (6 of) for a Fox 35X? I could probably find this out in a few minutes by taking one out of an engine, but as I don't want to disturb the head after a recent rebuild (29X) I'm not bothering. (I think they're 1/4") I also need a prop nut too.
Incidently I've stumbled on an foolproof method for making the 23% mix required for these engines;
I use model technics Contest 10 (10% nitro with 18% EDL oil). To make 1litre I simply make the fuel up in two parts, adding 50ml castor oil first off to make the total oil content approx 23%.
This works well with a fox no8 plug, and I use these in all my fox strokers!
......... I'm investigating mixing different nitro contents next. O:-)
Tim
PS The Scaremonger FA1 46" Ironmonger is well on the way to being finished - just hope that tank lasts this time!!!
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The original head bolts (screws) were 7/16 inch long. Most that come now from the factory are 1/2 inch long and often "bottom out" before hey tighten down onto the head. I always grind off about 1/16th inch of the end of each screw so as to be sure that the screws don't "bottom out". I believe that this is easier than trying to drill the holes deeper and re-threading them.
Bigiron
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Cheers BigIron,
I'll order some from Westfield Fasteners, also am I right in thinking that the 'X' series Fox motors are the same aluminium piston/steel liner design akin to the 35 Stunt? (I'm trying to get an ideal oil content for running them. - I understand the combat motors will be fine on a leaner fuel mix mainly due to the needle roller bearing crankshaft).
Tim
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Most of the "X" series of engines are Iron piston and steel sleeves. I would run 22 to 25 % castor oil fuel and 15 to 25% nitro..
Bigiron
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Nearly right then! I've actually found a place not all that far from me which sells bottles of pure nitromethane and methanol. - As I've got more than enough castor oil at the moment, it would probably be an idea to have a go at making my own glowfuel. (Only problem is they don't send it by post, for obvious reasons!!!).
I'll see how I get on with my 10% once the planes in the air. - I might even by some 25% nitro and mix it 50/50 with what I've got. (Only have one branny engine out of the three I've got, and don't really want to have to use it as a donor when a crank lets go!)
Cheers,
Tim
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Tim, If the crank lets go, I have some spares in the junk barrel.
Bigiron
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Thanks Bigiron! Seems to be the Achilles heel on those engines!
I believe the metallurgy wasn't great for some reason. I suppose they were building them to a make a profit and probably didn't realise they'd still be sought after fifty years later! (Pity they never used machined crankcases with the earlier ones either. - I love these engines,
like a 35 Stunt on steroids.)
Tim
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Got some 1/2" UNC 4 - 40 hexbolts and cut them down to 3/8" (same size as the knackered ones that came out).
The 4 bolts for the backplate are 1/4".- Kept the gaskets on as I didn't actually remove any parts, and now the engine performs well with a 9*8 Topflite on 17.5% nitrofuel!
(I turned each bolt through a UNC 4 - 40 die after cutting to ensure there were no burrs on the end of the threads.)
Tim