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Author: Subject:  Brake Drums - a word of warning! Greg Mackie
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posted on May 30th, 2010 at 06:14 PM



Here is the promissed photo of the device...

http://www.flat4.org/gal/albums/userpics/10201/BILD1681.JPG
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posted on May 30th, 2010 at 08:13 PM



Thanks John, but rather than a 'Band-aid' fix, I will most probably be using Type 3 drums (genuine VW ones).

The chassis is OK and so are most of the suspension bits. Engine and gearbox look good - not even a bent axle.

A roll cage is a definite for the re-build!

Cheers, Greg




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posted on May 30th, 2010 at 08:53 PM



I noticed all three mirrors are all good two greg,
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posted on May 30th, 2010 at 09:15 PM



Quote:
Originally posted by HappyDaze
Thanks John, but rather than a 'Band-aid' fix, I will most probably be using Type 3 drums (genuine VW ones).

The chassis is OK and so are most of the suspension bits. Engine and gearbox look good - not even a bent axle.

A roll cage is a definite for the re-build!

Cheers, Greg


That's OK Greg, this applies to F Vee only, because of regulations...they can not use other than type 1 components../ as you would know :lol: /
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posted on May 30th, 2010 at 09:26 PM



Quote:
Originally posted by johny rotten
not many 1200 / drum brake vees running any more

most are 1600cc disc brakes etc now


Yes most Formula Vee cars have gone to disc packages even many of the 1200's. The Historic guys still run drums and the other "problem" we battle with is left stub axles .... this we solve be bolting through the speedo cable hole.

Regards,

Ian




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posted on May 30th, 2010 at 09:49 PM



Quote:
Originally posted by HappyDaze

A roll cage is a definite for the re-build!

Cheers, Greg


A VERY smart move Greg.




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posted on May 31st, 2010 at 07:06 AM



Quote:
Originally posted by 71-BEETLE-SEDAN
I noticed all three mirrors are all good two greg,


Yeah Josh, that's so that I can LOOK BACK on all this and say "What a great bunch of people the VW crowd are - all those offers of help, and good wishes were very much appreciated".

Cheers, Greg




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posted on May 31st, 2010 at 07:17 AM



Quote:
Originally posted by chequer57
Quote:
Originally posted by johny rotten
not many 1200 / drum brake vees running any more

most are 1600cc disc brakes etc now


Yes most Formula Vee cars have gone to disc packages even many of the 1200's. The Historic guys still run drums and the other "problem" we battle with is left stub axles .... this we solve be bolting through the speedo cable hole.

Regards,


Ian

I know Vees need to comply with the rules, but as I CAN up-grade, the stronger drums are a better option.

Thanks for the stub-axle-bolt tip Ian, I like the idea.

Cheers, Greg




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posted on May 31st, 2010 at 08:33 AM



May I ask why your not going to go to rear discs?



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posted on May 31st, 2010 at 08:52 AM



Quote:
Originally posted by trickysimon
May I ask why your not going to go to rear discs?

Just 'Oldschool' stubbornness, I suppose!




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posted on June 6th, 2010 at 09:06 PM



Hi all,

Greg Mackie has sent me these photos and asked me to post them up. These are obviously photos of his fractured brake drum/hub. I will just explain that Greg has manufactured and fitted a cooling system to the drums to radiate heat, hence the cooling vanes.

You will also see the baking plate is extensively bent fromt he fractured hub, yet has not caused any damage to the axle or the axle tube.

Regards, Kev

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posted on June 7th, 2010 at 08:56 AM



Im guessing that the outer ring and vanes are aluminium and an interference fit to the drum?
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posted on June 7th, 2010 at 11:59 AM



The rings I know are aluminium, as far as I know from what greg told me they are just heat shrunk onto the drums.

Someone correct me if i'm wrong though..:?:




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posted on June 7th, 2010 at 11:59 AM



Correct guess! The cast aluminium rings are machined to suit the drum O.D., -0.035". Drums do not need to be machined.

The first time I did this mod. was in 1962 and it kept the drums nice and round, as well as improving the cooling.

If I had known about Frank Klienig's ' safety disc ', there may have been a better result when the drum collapsed, perhaps?

Cheers, Greg




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posted on June 7th, 2010 at 12:47 PM



Quote:
Originally posted by HappyDaze
Correct guess! The cast aluminium rings are machined to suit the drum O.D., -0.035". Drums do not need to be machined.

The first time I did this mod. was in 1962 and it kept the drums nice and round, as well as improving the cooling.

If I had known about Frank Klienig's ' safety disc ', there may have been a better result when the drum collapsed, perhaps?

Cheers, Greg


No chance to research it yet or run it past some metalurgists but I'm wondering about the thermal expansion rates of the aluminium vs the steel. The aluminium would also be sitting at a different temp to the steel so even if the expansion rates are the same there would still be a difference in the growth of the metals.

I've seen similar set ups on drums that end up glowing red during racing, but the finned metal has always been the same as the drum.

I'm curious if your drums would ever get hot enough that the aluminium starts to "choke" the drums expansion. Even still, I would expect the aluminium to fail before the steel stresses excessively in the middle.


Just thinking out loud...
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posted on June 7th, 2010 at 01:52 PM



For a start the drums aren't steel, they're cast iron. As aluminium expands at a greater rate than iron, the ring would probably be more likely to come loose than 'choke' the drum.

I ran that set-up for many road and race miles in the early '60s on a Beetle (100MPH stops at Bathurst, Warwick Farm etc.) without a single problem. Also the present car has done almost 4 years of racing, on the original (50 years old) drums, with the fins fitted, without any trouble. The drum that failed was brand-new Zimmerman, fitted for the Nats. Supersprints :!:

Cheers, Greg




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posted on June 7th, 2010 at 04:37 PM



Just a thought Greg. Got anyone lined up to look at the shards?
Had a metallurgist look at some failed "forged" name brand pistons which turned out to be simply cast and hot pressed on the crowns. I think you might find some rather ordinary casting in those drums.
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posted on June 7th, 2010 at 07:29 PM



'rather ordinary casting' is probably being kind, Matt. A friend of mine has been in the industry for many years, and he will be 'checking it out' for me. This could take a little time, but meanwhile it is important for us to think carefully about the 'repro.' bits that we are using. I certainly have learned a lesson from this.

Cheers, Greg




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posted on June 21st, 2010 at 03:46 PM



geez this is scary. life relying of a piece of cast iron.



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