Hi, I need to make some brake drums for my R. Normally I'd cast and machine them in cast iron but they are 12.5"diameter and I think my chances of gettng good cast iron with no chilling is just about zilch from past experience. Is there any problem with making these from steel. I can use thick walled steel tube with a steel discc welded in and then machined. The drums on Model T Fords were steel I think and with using woven break linings , I cant see there would be a problem. Incidentally, does anyone have a source for the brake lining material? Any advice welcomed!

thanks

jeff

I'd try to find something to modify before I went to those lengths. I'd start with Ford 250 or 350 drums - they've got to be about that size. If that won't work there are trailer brakes in various sizes, especially the ones used to move mobile homes around. Several years back I worked on a plane tractor (one of those little haulers you see at airports towing planes around) that had rear drums that had to be at least that size, or maybe larger. I don't know who made the brakes, but I'll bet they were right off the shelf.

Cast iron brake drums are light years better than steel brake drums. They cool better, brake better and don't warp as easily from the heat as do the steel ones. Turn some new drums out of "off the shelf" brake drums. Do a search on this forum for brake lining. Rolly Evans came up with the best brake lining yet. It lives well with the steam cylinder oil and it stops well too.

Ok cast iron it is then! I did a search for drums a while back but the problem is they tend to just go by part number and there are no dimensions. The other problem is they all tend to be predrilled. I could pludg the holes but putting in a second set would weaken them sustantially. Does anyone know of a drum manufacterer that I could contact?

Jeff

A second set of holes usually doesn't bother the strength of the brake drums. Careful placement of the new bolt pattern is helpfull to success. I have gone through this redrilling of double sets of lug holes over and over for years. Haven't had to plug any of the old holes yet.

Jeff go with Ductile iron 85-55-06 it’s a lot stronger 85,000 t, 55,000y

Rolly

Jeff I used the lining used on crane brake drums it can get oily and wet and still hold. I can’t get you the name of the stuff till April.
Rolly

Thanks Rolly, at my rate of progress I may not need it until then!

Jeff

Anybody have a line on a couple of 14" diameter cast iron brake drums that use 2"wide lining? I can machine them myself if I can get the castings. They are to fit the condensing 1919 Stanley model 735. If I have to, I will make up a pattern and have them cast. Modern drums have a too large of center hole. The center hole I need cannot be any larger than 4" I.D.

Just checked my pattern, it is only 13" diameter

Jeff

Jeff, On your modern drum size question, most parts houses in Northwest Washington have brake drum catalogs that list all of the modern drums' dimensions. I found many 14" drums, but they all had a middle hole dimension that was much too large for my needs. I am still looking.

Yes, I gave up looking and made a pattern and got them cast. I think it was probably quicker and cheaper in the end!

Jeff

Jeff, Good looking brake drum. I guess that I will have to do the same.

Jeff and Rolly, When making my brake drum pattern, What percentage of shrinkage for Ductile iron 85-55-06 should I allow for? and.... Allowing for warpage and finishing in the pattern too, how much larger and smaller should I allow in the pattern for that? Internet says: "The shrinkage allowance will be different for different metals. The shrinkage allowance is greater for cast steel than that of other alloys. The shrinkage of the metal mainly depends on the metal or alloys to be cast, dimensions of casting, moulding conditions, pouring temperature etc., The shrinkage allowance is always added along the length than along the diameter." My machinist handbook says for cast iron: to allow 1/8" per foot for shrinkage.



Edited 1 time(s). Last edit at 06/16/2016 10:30PM by SSsssteamer.

I use between 1/16" and 1/8" per foot depending on thickness. Anything over 3/4 " thick would use 1/8". I think I used 3/32" per foot on my pattern. I always make my patterns overly generous where they are to be machined so that I can take deep cuts to start with to get under the casting surface as that is what wears the lathe tool out being the hardest iron. I would allow about a 1/4" outside the finished dimension but you could probably go a lot less. With a brake drum, you shouldn't have any warpage problem as it is a reasonably stiff shape.

Hope this helps.

Jeff

Thank you Jeff. I will use your figures. It doesn't bother me to machine down an extra amount of ductile iron as ductile iron is really nice to work with. "Metal is always easier to machine off than it is to put back on."

My 14" diameter brake drum pattern is now at the Thompson Foundry is Surrey, B.C. I will let you all know how the drums turn out. As a side note, the foundry said that I didn't quite have enough relief in my brake drum pattern. They will put the outside of the pattern on a belt sander to sand some clearance there and for the inside they will smear some body filler around on it. All so that pattern will pull out of the sand a little easier. I am having some outside rear Stanley hubs cast out of 4140 too

I finally got my brake drum castings back from the Thompson foundry. They machined up very nicely. Since these drums are a little bit beefier, I have to buy some new brake lining to match them, so I still have a few weeks before I get to try them out. In the photos are: the worn out drum, the new drum casting, and a finished drum. Last photo is the installed cast iron brake drum.

As always Pat very nice work.
Rolly

Rolly, Thank you for the complement on the brake drums. I went with the Ductile iron 85-55-06 as you suggested. They machined out wonderfully.
On these 14" diameter drums, I had to fight tool bit chatter. When I got out to the end of the outside cut, they would ring loud like a fine brass bell and tool bit chatter resulted. I have a 10 pound slab of lead that I use as a backing for punching out holes in gaskets. I pressed the lead slab onto the drums while doing the last 1/2" of turning and it completely stopped the ringing/chatter. In turning the inside of brake drums, usually a rubber strap is tightly wound around the outside of the brake drum to dampen the ringing. What would you use to dampen the ringing/chatter while turning the outside of your drums? Thank you.

Pat I don’t remember having a ringing problem. Maybe because they are smaller.

Rolly