| Author | Message | ||
     David Gore (63.60.243.84) |
I recently received a request from one of our NSW Branch members for information on reconditioning brake drums that have reached condemning size as an alternative to purchasing new drums. As I believe this topic will be of relevance to all owners of pre-Shadow models, I would appreciate input from anyone who has had any experience in reconditioning brake drums or industrial products in applications involving wear, thermal cycling and safety requirements involving avoidance of unexpected and/or catastrophic failure of the reconditioned product. The following techniques could be used to recondition the drums: 1. Machine the drum true and parallel before thermal spraying a suitable coating. 2. Buid-up the internal diameter of the drum by submerged arc/laser welding, stress relieve and machine to original I.D. 3. Machine the I.D. sufficiently oversize to allow a sleeve to be fitted and attached to the drum. All information and/or opinions will be appreciated regardless of whether the application was successful or not as there is always something to be learnt. Thanking you in anticipation. David Gore - Technical Officer NSW Branch. | ||
| Bill Coburn (203.51.25.155) |
David/ The drums for the Cloud series which concern me appear to be forged castings with a steel liner. I suspect that this accounts for the horrendous price of the units. Robert Chapman has produced cast iron versions which have very good reports and they come at about $400 each almost a quarter of the original. Sleeving these units while seemingly the obvious step is apparently unsuccessful for mere mortals. How the Factory did it is unknown to me. | ||
| Bill Coburn (203.51.25.155) |
David/ The drums for the Cloud series which concern me appear to be forged castings with a steel liner. I suspect that this accounts for the horrendous price of the units. Robert Chapman has produced cast iron versions which have very good reports and they come at about $400 each almost a quarter of the original. Sleeving these units while seemingly the obvious step is apparently unsuccessful for mere mortals. How the Factory did it is unknown to me. | ||
| Jim Bettison (203.166.57.11) |
David, I recently had the luxury of a week poking around in middle-England looking at "the scene" as applied to MkVI, R-Type, S Wraith, Dawn, etc. with the guidance and companionship of a well-learned RREC member with all the right contacts. Amongst others we called on Ristes at Nottingham and Healey Bros at Irthlingborough. On the way home I lost all my diary notes in Singapore. HOWEVER, it is my recollection that new brake drums to RR specs are being produced, and that they are not such a dreadsome price as previously. Therefore, I suggest that you check out with at least these two manufacturer/suppliers. I can get you names and addresses if you want. Jim B. | ||
| David Gore (63.60.7.175) |
Jim, I would appreciate email addresses for these suppliers if your UK contact can forward them otherwise I will have to rely on the internet UK Phone directory and the trusty fax machine! The member has a R-Type which has no machining allowance left on the drums and the current oversize brake linings result in erratic braking as the vehicle comes to a stop. I was very interested in Bill Coburn's advice about the Cloud composite units as this indicates resleeving could be possible with the right techniques and quality control. Thanks for your contribution and if you get the email details, could you please forward them to me at "technical@nsw.rroc.org.au". | ||
| Richard Treacy (217.162.168.47) |
I replaced my front drums of my R-Type in Canberra some years ago as they were well past the wear limits. I was using spacers under the linings for a number of years and they worked perfectly well. However, it was time for new ones so I bought a secondhand unworn pair at Healey Bros for £55 each in 1989. I only put them on the car in 1992. At the time I explored renovating my old ones. I was warned away from sleeves on safety grounds, but this may have been overly cautious. The only method recommended at the time was spraying the surface and machining them to new spec. This brings two problems: distortion and short lining life, so the pair I bought seem to have been the best value and the safest option. If I could have bought new ones I would have done so. I really believe renovating the drums should be avoided if possible as it is costlier in the long run and a second-rate solution. Regards, Richard. | ||
| Robert Chapman (202.161.111.148) |
R.A.Chapman Automotive has been manufacturing Cloud brake drums since 1989. Conscious that these are extremely safety critical parts and suffer high thermal stress we concluded that any method of repair was a very poor option. We had a dedicated pattern made and the drums cast in one piece in the same manner as 99% of cars and commercial vehicles on the road. These drums have the advantage of a higher coefficient of friction between shoes and drum therefore giving a more responsive feeling brake, and a replacement cost of approximately one quarter of original. They have been proven over many years and miles by private owners and wedding car fleet operators, both in Victoria and interstate. We are also exporting our drums to the USA with very good feedback. | ||
| Jim Bettison (203.166.57.12) |
David, Sorry about delay. We've had powerline problems - surge followed by blackout - and it did no good to open files. Guess where my reply to you was ... So much for surge protection. I ahve a recent catalogue from Ristes that includes brake drums for MkVI/R-type at 395 pounds each. Their e-mail is info@ristes.zee-web.co.uk I remember a conversation with them about brake drums, amongst other things - see later. I believe that they are making these drums. I also had contact with Healey Bros at Irthlingborough; their e-mail is experts@healeybros.co.uk Although they don't list brakedrums in their catalogue, they are good at sourcing new, replacement and used parts and getting them exported at minimum cost. (From my own experience.) As you probably know, these firms are members of the 30-strong Rolls-Royce Bentley Specialists Association, which includes 5 Australian companies. One of these is R A Chapman Automotive, who have contributed above to this discussion. In passing: both Chapmans and JP Pistons were very well spoken of by those in the UK of whom I enquired - which I find very gratifying - although brake drums weren't a matter I followed exhaustively. I did learn that the MkVI/Dawn/S. Wraith/etc brake drums are cast with an included steel insertion, which accounts for their cost, and for the limit placed on oversizing the drums; it is necessary not to grind into - or even too close to - the steel, but instead to make sure that there is adequate cast iron thickness between the inserted steel and the contact face. Reasons given me for this design were several; control of "squeal", control of drum expansion and shape under heavy use were two that I remember. I don't have any experience of drum reconstitution by metal spraying or welding techniques. I have heard that the local Bugatti Club had some respraying done some time ago, and I think it was successful. On the other hand, attempts at sleeving were not successful. I can imagine that a sleeve could have problems of heat transfer, compounded unless coefficients of thermal expansion were very close. Would you like me to follow-up on the successful outcome, perhaps identifying someone who did it? Another commnt: I think that some members of the Specialists Association may be manufacturing substantial quantities of items, with an intra-asssociation trade in parts being active. I would not be surprised if large parts retailers/suppliers who are not Association members are also sourcing from these manufacturers. Let me know if I can assist further. Jim B. PS: I make the usual disclaimer of interest or reward in any of the enterprises mentioned. Also, I have not seen all or many of the industries who are offering these goods and services, and must therefore indicate that my overview is incomplete. | ||
| David Gore (63.60.241.162) |
Jim, Many thanks for your comprehensive and interesting information. As a qualified metallurgist, I have refrained from expressing my personal opinion on reconditioning until I was able to ascertain if technology and experimentation in recent years had been able to overcome the past problems that I was aware of from the 1960-1990 era when I was actively involved in the profession especially in regard to plasma spraying for rebuilding worn surfaces. I would be very interested in contacting anyone from your Bugatti Club who was involved in their exercise to discuss their experience in more detail. | ||
| Jim Bettison (203.166.57.11) |
David, On investigation I find that the Bugatti Club didn't proceed with the plasma spray proposal, as it was felt that the price (around $400 each drum) was more than they wanted to pay. I don't know what they eventually did. However, the same technique was subsequently used successfully on brakedrums from a Hudson, or similar large (>10" dia) American vehicle, I was told. The work was done some time back (don't know exactly when) by Metallising Industries, 9 Johansson Road, Wingfield, S Aust; tel 08 8359 1000, fax 08 8359 0400. The contact there was Rob Brandenburg. I would be very interested to hear how your (or the owner's) problem is resolved. Good luck. Jim B. | ||
| David Gore (63.60.243.178) |
Jim, Many thanks, I have a vague recollection of the Company being involved in reclamation of mining equipment but I can not remember if this included obvious safety items such as winding equipment, transport vehicle parts etc. Plasma spraying was limited to an effective coating thickness of 1mm [0.040inch] after which the adhesion of the coating to the substrate began to deteriorate - the main advantage was the extremely close tolerances that could be maintained to the point that finish machining/surface grinding was minimal or not necessary provided the part had been machined true prior to spraying. I will contact Metallising Industries and discuss this application with them and post the information on this topic. Thanks to everyone who has contributed to this enquiry and shared their information with us. | ||
| Bill Coburn |
I am wondering where all this is getting us. Although I have not used them, what is the objection if any to the Chapman drums. I have heard no complaints about them and they seem to fit the bill. One thing I do like is that you keep the old drums. In the event of a catastrophic failure they are always there for re-use. I have a Cloud III which when the brakes get hot and you need to lay into them at high speed they produce the most remarkable rumble. So if anybody has adverse experience with the Chapman ones please let me know before I leap into this solution. | ||
| David Gore |
Bill, The R type drums were traditional cast iron construction whereas the Clouds appear to have had a composite unit comprising forged and cast components. The original enquiry concerned R tpe drums and the Cloud drums came in as a side issue pertinent to possible reclamation techniques. The original enquirer is sourcing after-market drums from Robert Chapman at 1/3 the price applicable to drums ex the UK suppliers - time will tell how these perform however, provided the foundry is reasonably competent and good melting practice followed, I can see no reason why the after-market drums will be inferior to the originals. I was never very happy about the idea of reclaming the worn drums due to the safety and technical issues involved!! | ||
| Bill Payne Experienced User Username: wimpy Post Number: 35 Registered: 1-2007 |
Just got an email from this company advertising a number of newly manufactured items for Clouds: www.post55parts.com As the company is within 20 minutes, I am particularly interested. | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 2058 Registered: 4-2003 |
Introcar offers brand new drums and rotors for all postwar cars by the way. http://www.introcar.co.uk/acatalog/index.html |
