Improving 55/56 brake systems

Discussions related to braking systems.
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Dave Czirr
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Improving 55/56 brake systems

Post by Dave Czirr » Fri Sep 23, 2011 8:01 am

Many of you know Ross Miller by reputation, if not personally. As he has done at quite a few PAC events in the past, he held one of his "Tech Sessions" one evening on the Henry Joy V Tour just past. Ross' experience is extensive and these events are not to be missed. This particular one took the form of a Q&A session and quite a bit of the discussion centered on how to get improved drum brake performance on the 55/56 senior cars. A few of the more interesting points were:

1. Use of the eccentric anchor pin was discontinued after the 54th series and hence getting full shoe contact adjustment in the 55/56 cars can be challenging, at the least. The discussion centered primarily on the senior cars. One thing to consider, at least for the front brakes (can't do on the 56 rears) was to use 54 backing plates with the eccentric anchor, or remove the fixed non-adjustable anchor and replace it with an adjustable anchor from the earlier models. This will permit a very superior adjustment with fuller shoe-to-drum contact.

2. If the drums are bell-shaped you'll never get good shoe contact with the drum. You don't want to turn drums unnecessarily but the surfaces MUST be parallel with the spindle or axle, so turn them if you have enough meat left.

3. Measure the drums to see if they are oversized (turned now or anytime in the past). If so, get thicker lining if you can and have them arc ground to match the new drum diameter. If this isn't possible and/or arc grinding removes too much of the lining, the old Chrysler method might be a good idea, though it will require that new linings be riveted. Chrysler for years recommended, when relining with turned drums, to use metal shims of appropriate thickness between the lining and the shoe such that the new OD of the lining matched the ID of the drums when the brakes were applied, thus giving 100% contact of the shoe with the drum.

4. The secondary lining does about 60-70% of the front braking effort in these Bendix self-energizing brakes, so it's critical to make sure you have the secondary (longer) lining in the correct position. Of course the original OEM lining for the secondary shoes was a different material than the primary with different coefficient of friction properties - but unfortunately today relined shoes have the same lining material on both shoes - unfortunate.

Certainly you'll never get the precise, linear feel of today's disc brakes, but you may be able to gain a very significant improvement as many "brake jobs" often consist of just lining and hydraulic component replacement without regard to reestablishing original full lining-to-drum contact area. Though it wasn't mentioned at the tech session, let me add that excessively heavy paint on the drums will inhibit heat transfer.

Adam
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Re: Improving 55/56 brake systems

Post by Adam » Tue Sep 27, 2011 4:53 am

Thank you for posting this Dave. Very interesting. I think I was able to hear some of Ross`s wisdom many years ago at a PAC National in Columbus.

As I read the comments I was reminded of the shims fitted between lining and shoe, and then you covered that too! I have read about it, but never seen it done. I have also seen the machinery for profiling linings and drums (particularly for heavy trucks) at garage equipment shows, but I have never seen them used. It seems to be very uncommon here.

Another thought, is that braking force is determined, I believe, by applied effort and coefficient of friction, coupled to leverage factors such as drum/disc and wheel diameter. For a drum brake, I believe the length of the shoe is a determinate of self-servo action. Lining area governs the rate of wear, not the braking force. Drum/lining profiling is important to minimse the wear rate and to avoid grabbing and squeal, whilst giving the best possible pedal feel.
"Do not underestimate the English cousin.....they are not as stupid as they look!" - Signor Altabani in The Italian Job.

Randy Berger
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Re: Improving 55/56 brake systems

Post by Randy Berger » Mon Feb 20, 2012 8:05 pm

This seems an appropriate place to pose this question, even if I am laughed at.
Does any know of a place where new steel can be installed on the drum and then cut back to original specs? Much like applying new tires on a steam engine - freeze the insert and then install it.
Does anyone know the original specs for 1956 drums??
I like the idea of installing 1953-54 front backing plates .

Dave Czirr
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Re: Improving 55/56 brake systems

Post by Dave Czirr » Mon Feb 20, 2012 8:19 pm

That's a really good question Randy, I've wondered about that myself. Though I'll never drive enough miles to have my drums turned to the limit and be looking for replacements, good brake drums are already an issue with some makes and models in the hobby. Many brake drums including Packard's were advertised as "centrifuse" and as I understand that, the actual frictional part of the drum, the inner portion which comes into contact with the lining, was composed of a sputtered cast iron-type material sprayed in a molten state as the drum was spun. And then of course machined to final dimension. I wish I knew more about this process but no doubt there is info to be learned by some research into it. If in fact that is true, then it would seem that drums that have been turned to their limit could be returned to original ID by the same or similar process. Metal sputtering has been around for a very long time and as you know is practiced in the auto industry in areas like spray welding (of crankshafts, for example). Steel as a final interior surface of a brake drum is entirely unsatisfactory as I understand it, it doesn't present an adequate mating surface to the lining to develop the friction needed. Or so I've read. Looks like we could develop some useful information here with a little diligent research into the topic.

I don't know quite what you mean by "specifications". Are you referring to ID, weight, or just what.

Adam
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Re: Improving 55/56 brake systems

Post by Adam » Wed Feb 22, 2012 1:35 am

I have also gleaned that steel is fairly unsuitable as a braking surface, I believe because of noise, friction and wear characteristics.

Certainly metal spraying, as we call it here, is a good way to build up a surface, but probably not the appropriate material for braking surfaces.

I would have thought it would be possible to shrink in a cast iron sleeve and finish the surface by machining after it was fitted. It would be a bit like fitting a starter ring gear to a flywheel. Perhaps it could be "keyed" to prevent movement. Although I have no experience of this.

There is a company not far from me called Typecast. They make replacement drums using a cast iron liner cast into an aluminium alloy drum and will work to any pattern. They have a very interesting website at http://www.brakedrum.co.uk
"Do not underestimate the English cousin.....they are not as stupid as they look!" - Signor Altabani in The Italian Job.

Dave Czirr
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Re: Improving 55/56 brake systems

Post by Dave Czirr » Wed Feb 22, 2012 7:27 am

Adam- thanks for that link. That was really interesting and thought-provoking. If only it weren't so far away and so expensive, plus having to provide a drum as a pattern, I'd really be thinking about it. 56 Packard brakes, particularly the heavy senior cars, are more prone to brake fade that we'd like. Many (most?) of today's younger driver's, having grown up in the era of disc brakes, have absolutely no idea how to drive a car with drum brakes in the kind of situations and terrain that causes fade. If you mention "if you need a lower gear to go up a hill, then you need a lower gear to go down", they have no idea what you're talking about. Hence many of them are looking at disc brake conversions which, to me as a purist, is just not an option. But ah - a set of those finned aluminum drums on the 56 - wow, that would be nice.

Randy Berger
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Re: Improving 55/56 brake systems

Post by Randy Berger » Wed Feb 22, 2012 10:46 am

By specs I mean inside diameter, depth of brake surface, diameter of original, etc.
How much can you remove? .010 or .100??
Is the braking surface cast-iron or cast steel? After reading the comments, I take it to mean that steel would be a poor surface for braking.
If you were to shim the lining to meet the drum surface, would aluminum be acceptable as it transfers heat readily??
I'm amazed that no one sleeves drums. But I have searched and found nothing.
Hmm, I wonder if 57 Buick aluminum drums would work. Now they have to be sleeved originally, don't they???

Adam
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Re: Improving 55/56 brake systems

Post by Adam » Thu Feb 23, 2012 5:52 am

Is the braking surface cast-iron or cast steel? After reading the comments, I take it to mean that steel would be a poor surface for braking.
If you were to shim the lining to meet the drum surface, would aluminum be acceptable as it transfers heat readily??


Hi Randy

I am sorry that I cannot help with the drum specs (do they not appear in the workshop manual?), but I am given to understand that steel does not work well as a braking surface. CI is preferable, I believe.

As for shimming the linings, I think you mean to shim between lining and shoe, a recognised practice at one time. In this position, any stable material will do since you are not altering the heat conduction properties of a standard lining/shoe combination in any case. In fact, you would not want to increase heat conduction into the shoe because that might heat the wheel cylinders more. Although it would not happen in this case.

Hope this helps.
Adam..
"Do not underestimate the English cousin.....they are not as stupid as they look!" - Signor Altabani in The Italian Job.

Adam
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Re: Improving 55/56 brake systems

Post by Adam » Thu Feb 23, 2012 6:06 am

Many (most?) of today's younger driver's, having grown up in the era of disc brakes, have absolutely no idea how to drive a car with drum brakes in the kind of situations and terrain that causes fade. If you mention "if you need a lower gear to go up a hill, then you need a lower gear to go down", they have no idea what you're talking about. Hence many of them are looking at disc brake conversions which, to me as a purist, is just not an option.


Dave

I think you have hit the nail on the head there. I was also taught that whatever gear you need uphill, you need the same one going down. Nowadays, new drivers are taught to brake in high gear, then grab a suitable gear to accelerate away from the junction or whatever. The thinking being that brakes are cheaper than clutches and gearboxes. I cannot bring myself to do this and prefer to be in a gear that gives me maximum control and instant response, so i will double declutch, even heel and toe, in a modern car as well as an old one. Except for my Range Rover, which is auto trans, but then I left-foot brake.

Back on topic, the ali drums are pretty pricey, but valid if you are going racing with an antique car. I would like a set for my Alfa one day. It has some ovality which is manageable on the road, but hideous on a circuit. Sadly cast and machined parts are getting more expensive all the time. To illustrate the state of materials prices, a friend of mine fell victim to the recent spate of thefts of catalytic convertors in our area, last week. They cut the exhaust pipe either side of the cat and take it for the scrap value (about £30-£40 per unit). Thefts of lead from church roofs and copper cables from the railways are a daily occurence. Sounds like a third world country doesn`t it?

Adam..
"Do not underestimate the English cousin.....they are not as stupid as they look!" - Signor Altabani in The Italian Job.

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