Brake Drums - a word of warning! Greg Mackie

HappyDaze · 2010-05-23T08:09:50+00:00

Nearly everyone knows by now that I managed to invert my 'Blackish' 59 Beetle at the Supersprints on Saturday. What is perhaps not commonly known is what caused this to happen.This is straight from the 'horses mouth'. As the original rear drums were worn in the splines, I decided to replace them with new ones for the Supersprints. This turned out to be a mistake, as the outside rear drum (brand new) collapsed under cornering load, and the result was a potentially serious roll-over. Fortunately, aided by good safety gear and some body strengthening, I walked away unhurt. I am well aware that I was placing a great deal more stress on the drums than was intended by the manufacturer, but I feel compelled to bring this to the attention of my fellow VW enthusiasts. Cheers, Greg

cb john Wolfsburg Wizard

470 posts · joined Jun 2007 · 30 May 2010, 6:14 pm

#781896

Here is the promissed photo of the device...

HappyDaze Superannuated

2,887 posts · joined Jun 2009 · 30 May 2010, 8:13 pm

#781924

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

I'd rather wear a Beetle out by racing it than by polishing it!

71-BEETLE-SEDAN AKA Josh

1,058 posts · joined Mar 2009 · 30 May 2010, 8:53 pm

#781929

I noticed all three mirrors are all good two greg,

cb john Wolfsburg Wizard

470 posts · joined Jun 2007 · 30 May 2010, 9:15 pm

#781933

HappyDaze wrote: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 😂 /

chequer57 Seriously Crusin Dubber

125 posts · joined Feb 2006 · 30 May 2010, 9:26 pm

#781936

johny rotten wrote: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

Formula Vee, preserving engineering museum pieces in Australia since 1964

Craig Torrens 6 times Australian, 7 times State Hillclimb Class Champion

8,040 posts · joined Jan 2003 · 30 May 2010, 9:49 pm

#781945

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

Cheers, Greg

A VERY smart move Greg.

HappyDaze Superannuated

2,887 posts · joined Jun 2009 · 31 May 2010, 7:06 am

#781980

71-BEETLE-SEDAN wrote: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

I'd rather wear a Beetle out by racing it than by polishing it!

HappyDaze Superannuated

2,887 posts · joined Jun 2009 · 31 May 2010, 7:17 am

#781982

chequer57 wrote:
johny rotten wrote: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

I'd rather wear a Beetle out by racing it than by polishing it!

trickysimon 100km/h is only 9 seconds away

1,473 posts · joined Dec 2007 · 31 May 2010, 8:33 am

#781988

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

HappyDaze Superannuated

2,887 posts · joined Jun 2009 · 31 May 2010, 8:52 am

#781989

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

Just 'Oldschool' stubbornness, I suppose!

I'd rather wear a Beetle out by racing it than by polishing it!

Camo Custom Title Time!

1,936 posts · joined Oct 2007 · 6 Jun 2010, 9:06 pm

#783322

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

I thought rebuilding a VW would be cheap - Shit I was wrong, just don't let the wife know !!!!

Click here for my (slowy) modded 1961 Beetle build.

HotRodMatt If it\'s old or rare - cut it!

3,616 posts · joined Sep 2002 · 7 Jun 2010, 8:56 am

#783365

Im guessing that the outer ring and vanes are aluminium and an interference fit to the drum?

sander288 "Bolt-on Master"

1,404 posts · joined Aug 2008 · 7 Jun 2010, 11:59 am

#783385

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..❓

BMW R65 LS
1967 1300 Deluxe
Swing-axles FTW ❗

HappyDaze Superannuated

2,887 posts · joined Jun 2009 · 7 Jun 2010, 11:59 am

#783386

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

I'd rather wear a Beetle out by racing it than by polishing it!

HotRodMatt If it\'s old or rare - cut it!

3,616 posts · joined Sep 2002 · 7 Jun 2010, 12:47 pm

#783395

HappyDaze wrote: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...

HappyDaze Superannuated

2,887 posts · joined Jun 2009 · 7 Jun 2010, 1:52 pm

#783402

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

I'd rather wear a Beetle out by racing it than by polishing it!

HotRodMatt If it\'s old or rare - cut it!

3,616 posts · joined Sep 2002 · 7 Jun 2010, 4:37 pm

#783420

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.

HappyDaze Superannuated

2,887 posts · joined Jun 2009 · 7 Jun 2010, 7:29 pm

#783461

'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

I'd rather wear a Beetle out by racing it than by polishing it!

vlad01 Compulsive Aussie Vee Dubber

4,270 posts · joined Jun 2010 · 21 Jun 2010, 3:46 pm

#786079

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

71 notchback,
Past owner of, 70 NB, 73 SB and 72 FB TLE