Mixing own glow fuel: total fail

A pity you had to discover it the hard way-but the practical limit for nitro and castor is around the 45% nitro mark....so yes, your mix of pure nitro, pure castor and pure methanol will separate out at a 50% nitro level, into a biphasic mixture. Easily rectified though by a) using a modified castor such as benol, rather than pure traditional castor or b) by addition of a low % of acetone -something around 3-5% to facilitate mixing.[you could try other organic compounds, but acetone is both cheap and readily available] Not sure what happens when you go to ridiculously high nitro levels such as 65% or 70% as people who did go there used synthetic oils, plus propylene oxide as an ignitor....and PO itself may also have assisted mixing.

ChrisM
'ffkiwi'

thanks for the great explanations Ken and Chris. I use 25% nitro and have been using Castor M which I thought would be ok and maybe it is. I recently found out it is 50 weight castor and is for use in speedway sprint cars. Maybe being 50 weight is ok, but im going to change to Benol as I think it may well mix in better and hopefully wont glug up my fuel tanks, reeds, TD venturi holes as quickly and badly as Castor M seems to. I know flushing it all after use would also help but I think the move to benol will be worthwhile.

Yabby...sometimes odd things happen-I recall many years back -sometime in the 80s one of our club members (Dunedin MAC, NZ) whinging about oil..'this bloody castrol isn't any good'....and producing a bottle of 'milk' to prove his point. He was always a bit of whinger so there wasn't much sympathy expressed................then it happened to me....again Castrol M....and Shell Racing Spirit [the latter to the uninitiated is methanol with about 2% acetone and some purple dye added...largely sold for bike racing....but it was a cheap source of methanol back then]

Was it a dud batch of Castrol M? or simply a case of 'improved' Castrol M with additives that reacted badly... I couldn't say-but we steered clear of it after that. And the 'milk' reference was apt-that's exactly what the mixed fuel looked like... It was about that time that the club developed a keen interest in Castrol MSSR as lubricant. AFAIK this was a peculiarly Australasian lube...IIRC developed by Castrol Australia specifically for model engine use....and seemingly only sold in Oz and NZ. I guess they had a modeller on the R&D team at Castrol Australia. I believe it was a blend of synthetic EP gearbox oils....but it worked well for us, burned very clean and left little exhaust mess, unlike castor.

Unfortunately it became ridiculously expensive....I think it was $80 NZ for 4-litres in the mid 1990s-the last time I recall pricing it.....and eventually priced itself off the market. Some people-since-have complained about rapid engine wear-but I never heard anything mentioned about that at the time when it was popular....and I used it in diesels as well as glow....

ChrisM
'ffkiwi'

I used to mix my own fuel. Had a liter of reagent grade nitromethane and made up some fuel for my Pee Wee 0.020's. I actually ran these little engines on 5% and 10% but found the needle tricky to adjust. When I mixed up some 30% fuel, that little engine opened right up. I've read about 70% nitro fuel for pylon racing but how many of us here are following that path?
At my age I'm happy to drive the speed limit and not have the fastest model.
So back to fuel: 30% or less should be adequate for most of us I'd think.

Neat castor and most of the stuff bottled for engines isn't the same thing. Probably all two stroke castors are modified/blended to allow blending with gasoline and reduce deposits. Neat or mainly castor oil is ~50 weight. The 30 and 40 weight castors are blended. Years ago, I had some old Sig castor (no idea how old) that stopped blending when making diesel fuel.

If you can get it, Maxima Castor 927 is a premium oil which runs clean and doesn't gum up quickly. 25/25 fuel is no problem.

Thanks to everybody on the feedback. Just as an explanation why I would go so high as 50% nitro, I was on the crew of a combat flier many years ago. He flew a modified Fox 36x with Blast. Now no insult meant to anyone who likes Wen Mac, but I found those engines to be underpowered. We built a special, very lightweight stunt plane for the Wen Mac and we used Blast to give it a goose. It flew and stunted very well. At that point we also discovered that as long as the gaskets in the engine were metal, the Blast could not chew them up. So I've been addicted to high nitro for my small engines ever since. Maybe not 50% but at least 30. As we all know, supplies for C/L, and especially small C/L, have disappeared from the shelves. At the time I was trying self-made mix, full synthetic oil was in. But the literature said the little engines didn't like full synthetic. Anyway, my problem was abandoned years ago. Thank you very much for your insight.

Thanks to everybody on the feedback. Just as an explanation why I would go so high as 50% nitro, I was on the crew of a combat flier many years ago. He flew a modified Fox 36x with Blast. Now no insult meant to anyone who likes Wen Mac, but I found those engines to be underpowered. We built a special, very lightweight stunt plane for the Wen Mac and we used Blast to give it a goose. It flew and stunted very well. At that point we also discovered that as long as the gaskets in the engine were metal, the Blast could not chew them up. So I've been addicted to high nitro for my small engines ever since. Maybe not 50% but at least 30. As we all know, supplies for C/L, and especially small C/L, have disappeared from the shelves. At the time I was trying self-made mix, full synthetic oil was in. But the literature said the little engines didn't like full synthetic. Anyway, my problem was abandoned years ago. Thank you very much for your insight.