JB Atoms

Wow Klippy, you do like your challenges, don't you!!

Anyway, good luck with the project, I'll follow it with interest.

Hi Klippy. First of all let me apologise for two things. One I'm sorry to send the engines in such a mucky state but I couldn't clean them on my lap. Second sorry for the struggle you've had to dismantle them. Now re the piston collar I unscrewed it by clamping a small jubilee type clip with a layer of rubber under it round the piston after heating a bit. I then squeezed the tips of a pair of pliers into the collar alongside the gudgeon pin .Very tight squeeze . Then using a round jawed vise grip round the clip and and a vise to hold the pliers handle gave it a pull . It didn't take an awful lot of power to crack the thread. I suggest using a thread locking compound of some sort on reassembly. I had forgotten about the threaded insert on the crankshaft since I lost the missing one's pieces a long time ago ,but did recall the thread size as being 2 BA. Talking of BA threads I've been trying to find some 5BA capheads screws Or one really to use as a comp screw for a DC Dart.Tried all the usual model fixing suppliers to no avail. Tried a local one man band engineering/tools supplier. No problem he said. Would a thousand be enough LOL. Ordered 10 price 90p and free post too P.S. I've never had any reports of either the piston collar or the C/shaft extension working loose I suppose the shaft and insert could be drilled through and pinned/riveted just aft .of the tapered area.The shaft is big enough I think. Cheers and thanks again Klip looking forward to next episode.

OK Tony I see you have discovered the secret of the Atom. All steel running parts including the cylinder. This lead to prolonged running in times and the less than glowing reports from the reviewers. I like them very much. Even though not fully run in I've had some really good speeds from them. Hence the point about one hurting Dad's ears.
However I don't get the point about the Dural con rods opposed to the original steel for longevity.Can you clarify this point for me please. I enclose a report on the Atom by Ron Warring in Sceptre Flight. I think Chinn and Sparey did one each too.
sceptreflight.net/Model%20Engine%20Tests/J.B.%20Atom%20(2).html
Good idea re the nick in the piston rim if it's not too brittle.
P.S. Don't worry about the damage near the N.V.A. I can get some J.B. Weld Epoxy or similar or use some Alloy solder when I'm about again. Got last preop on Monday .Chest X-ray which they couldn't squeeze in last week. Fingers crossed.

one tenor wrote: OK Tony I see you have discovered the secret of the Atom. All steel running parts including the cylinder. This lead to prolonged running in times and the less than glowing reports from the reviewers. I like them very much. Even though not fully run in I've had some really good speeds from them. Hence the point about one hurting Dad's ears.
However I don't get the point about the Dural con rods opposed to the original steel for longevity.Can you clarify this point for me please. I enclose a report on the Atom by Ron Warring in Sceptre Flight. I think Chinn and Sparey did one each too.
sceptreflight.net/Model%20Engine%20Tests/J.B.%20Atom%20(2).html
Good idea re the nick in the piston rim if it's not too brittle.


P.S. Don't worry about the damage near the N.V.A. I can get some J.B. Weld Epoxy or similar or use some Alloy solder when I'm about again. Got last preop on Monday .Chest X-ray which they couldn't squeeze in last week. Fingers crossed.

Btw this site may be of use or interest to you JO/T
sceptreflight.net/Model%20Engine%20Tests/Index.html

No FinM Tony I never thought about Imp V Metric sizes. Yep hard on hard is unusual but seems to have lasted OK on these two.I lost touch with my mate who had a matching pair so can't do a comparison. At least we have it with the crankshaft John

A very interesting thread, just wondering about the age of these engines?.
(Re your remark about your dad's hearing john).
Regarding the steel parts is it normal to have steel on steel? I thought the parts that suffered most wear would be softer metal so main parts would not require replacing, ie shells and crankshaft on car engines, is it not the same for these atoms? Boz

The JB Atom was the subject of an engine test in the April 1956 Aeromodeller
Mike

I believe Mills engines used hardened pistons and cylinder, and because of this were virtually impossible to wear out. A modern example of this set up is the very high quality Peter Burford 0.3cc engine. This explanation on his web site states that a small variation in hardness is enough to prevent galling. See www.peterburford.com.au/construction/
Doug

Interesting Doug .Thanks for that