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 Devcon suitable for fin repair?

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1bantamcloser2divorce

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Number of posts : 36
Localisation : Vancouver Island, CANADA
Registration date : 2009-10-06

PostSubject: Devcon suitable for fin repair?   Fri May 24, 2013 11:12 am

Hello,


Wondering if anyone can tell me if Devcon Aluminium Putty (F) has a thermal conductivity that would make it suitable for fin repair on my cast brrel. Sadly my barrels top fin is a bit of a jigsaw puzzle after a transatlantic trip with not very robust packaging.

I am exploring options for repair.

The Devcon information says a thermal conductivity of

1.73
[cal/(sec x cmx0) x 10 (-3)

This doesn't mean anything to me. Bottom line, will the Devcon conduct the heat sufficiently well to allow for adequate cooling?

Thanks,

Andy

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Derek

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PostSubject: Re: Devcon suitable for fin repair?   Sat May 25, 2013 7:00 pm

Hi - I would not use Devcon, it would be a temp repair.

options as I see them.
1) weld it
2) machine it off the damaged fin and shrink on a fin turned from alloy plate to the same size once fettled / if done well, not possible to tell.

I have just repaird three very old badly damaged barrel castings, far more damage than just the top fin, I heated them, removed the liners, had them welded then re-heat treated, before refitting new/better liners, the welds were fettled with a high speed flapper wheel, between the fins, it looks ok as can only just see its been welded, well only from the btm half, a bit of paint and it will look the business is W.I.P.

regards Derek
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1bantamcloser2divorce

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PostSubject: Re: Devcon suitable for fin repair?   Sun May 26, 2013 3:41 am

Derek,

Thanks for the reply. Unfortunatley I do not have welding gear and not sure I can affordhaving it done by someone else, so am looking for another solution.

I see your point though and food for thought.

Cheers,

Andy
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john bass

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PostSubject: I wonder why...   Mon May 27, 2013 6:38 am

I wonder why no one has used copper fins brazed onto an iron barrel?

Maybe I am wrong (If so I┤d like someone to say so) but Mackerle reckons by the testing he has done that copper-fins on an iron cylinder barrel transfer considerably more heat (twice as much as an all iron cylinder▓▓▓...) than any other system or combination. NOT COMMERCIALLY V╠ABLE -- too costly, of course, but in racing who gives a pooh about cost???

▓▓▓ I find this hard to believe but it is in his book, "Air Cooled Automobile Engines"
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john bass

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Number of posts : 1719
Age : 88
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PostSubject: PS ...   Mon May 27, 2013 10:23 pm

PS... to my last posting. A Chevvy had copper finned cylinders -- invented by Kettering -- and every car had to be recalled in 1923 which killed off AC engines in cars for half a century. Besides, there┤s no hot water for cab-heating -- just not acceptable in the US of Big A....
Aircraft engines have seen a lot development since, but then they are frequently expected to run at only two loaded engine speeds: either flat out for take-off or at a reliable cruising speed. Intelligent electronics show now where difficulties are and there then exists a compromise of Cost versus practicality of production with public opinion and acceptance. Such as Peugot AC engined specials are an example: speeding with reliability on public roads --and in competition... AT A PRICE!!!
With Auto engines the loads and speeds are varying widely (and wildly) over a large speed range so to achieve the `ideal┤ is very difficult. With an AC Bantam `Staggered, Intermiiten & different material fins┤ must have all been tried but I still wonder if something on these lines is possible. One would need an air-fan and that immediately looks wrong with horspower needed to run the oil-pump but it can be done -- expensively. The absorption of power by the oil-pump might well be offset by improved engine output. An obvious question is why have fins all the way along when only a small part of teh air-route is ver-temperature?
Our V-8 diesel engine intended for the American military had a fluid flywheel drive which operated when a tempertaure-sender said there is a part of the engine that is too hot and the fan then comes on to direct air by well-developed ducting at the hot spot....

How terribly boring -- yaaawwwnnn!
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1bantamcloser2divorce

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PostSubject: Re: Devcon suitable for fin repair?   Thu May 30, 2013 6:56 am

Well , I decided to experiment. i have an old cast iron cylinder too far gone with corrosion to be of any use. I cut a portion of a fin off with a Dremel and then re attached it with Devcon aluminium putty.


[img][/img]

Then I used a blow torch, via the inlet manifold, to heat the barrel over half an hour, starting at room temp. up to 100 degrees C.


[img][/img]

I switched a temp sensor back and forth to compare the temps between the repaired and non repaired side. The temperature difference was never more than three degrees, with the repaired side equalizing within a minute or two.

A good project for a rainy day!
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