Getting ready to have some underslinging brackets built for the T speedster and was curious if someone can go over the advantages/disadvantages of cast manganese vs. cnc steel; Here are the details; Brackets are approx. 4.5" long by 1.875" wide. The spring perch boss is approx. 2.5" deep and the axle pad is 1.5" tall. Original brackets were cast from manganese but I'm unsure if there are any foundries that would be willing to mess with a one-off set. Since I've only been able to work from photos and detailed measurements I'll be making up a wooden master to copy from. Here are the photos; Any thoughts?
My thoughts would be, if you have no way to hammer forge the cast parts then I would make them from a solid block of steel, preferably something that could be properly heat treated and drawn back.
It depends on how period perfect you want the finished result to be. Can you explain what the brackets do? I'm a little fuzzy on that. If the originals were bronze I doubt you will have any strength issues with steel or even iron brackets. Have you seen LOUDPEDAL's excellent thread on casting stuff? http://www.jalopyjournal.com/forum/showthread.php?t=464599
Im confused on the terms. Manganese bronze is typically used in the marine industry for its anti-corrosion properties. Manganese bronze also isn't as strong as steel. Manganese steel alloy is a very strong alloy that is often used in casting high strength parts. The parts you show look like steel not a bronze alloy. I may be wrong, just my 2 cents.
Fellas, The brackets move the axle up and out in front of the spring. Here's a rough drawing; (front brackets shown on right) As far as construction, the originals were made from manganese bronze. There were many other 'underslinging' brackets that were made the same way...
I'd be more tempted to make the parts from something like a 4340 steel myself. It has good fatigue strength and toughness, machines nicely enough and is easily heat treatable. Check the link below for specs on 4340 steel. Bob http://www.suppliersonline.com/propertypages/4340.asp
I'd imagine a decent cnc protoype shop would have somebody on hand hep to the metallurgy business, or at least sufficiently so to recommend an appropriate alloy... you're in TX, there's probably somebody local to you who does custom parts for the oil biz. Won't be cheap, though.
Yup. Re; the advantages/disadvantages. Casting makes a cheaper part in production. Bronze as a choice? Is there any movement with the associated parts? If so, bronze is more lubrous than steel, and usually chosen where you want a "cheaper" part to fail. I.E. a small spring perch rubbing on a big spring. The spring is expensive, you don't want it to wear out. So you make a wear point, the perch, and you let it wear out. Again, the bronze is tough as hell and lasts a long time, but it won't out last the mating steel component. If there are no wear considerations, then choose an alloy steel like bob mentioned. We use a lot of 4140/4142/4340 in the tool and die industry. A couple of reasons, tough as hell, pretty easy to work with, heat treatable, and responds to tempering well. The ability to temper nets great strength with better resistance to fracture. If you are interested in making the alloy steel part look like the original, most molds are/were built with a 1.5-3.0° of draft to them. You can buy end mills specifically for cutting with these angles. Surprisingly enough, they are called draft cutters. To reverse engineer this part and get cad data for it, many machine shops now have CMM's. They are a great tool for reverse engineering almost anything. We have done everything from electric guitars to car and tractor parts with ours. Usually takes less than an hour for simple parts like yours, or dozens of hours for doing surfacing and 3-d model generation.
That's great information! No, there are no moving parts, but they are subjected to a decent degree of stress. The original parts used bushings in the spring perch holes...evidently to provide sacrificial wear. The car, all told will weigh 1400 lbs so I'm not super worried about using manganese...my only issue is that there aren't a whole lot of foundries out there casting mb. As for reverse engineering the brackets, I've had to do that with photos. I do not actually have these brackets, as they are exceptionally rare. I was thinking about carving a mockup out of wood so that a casting mold could be made, but I suppose that would work with CMM as you described. If I go with steel, what ballpark are we talking about price-wise?
1045 is a good cantidate, Bronze is for bearings I wouldnt make the whole peice out of it.Also look into stainless 309 comes to mind but research it.
Based on your first picture, material included, probably in the neighborhood of $200-$300. That price is driven greatly by aesthetics. Will a squared off block with the holes in the right location suffice? If so, maybe $100. If you want it "profiled" so it looks exactly like your picture and it can be accomplished completely with draft cutters, $200. If it has to be picked, using a small ball end mill to get every surface just right, $350 and up? We figure around $10 per pound for the alloy steels until you get into the bigger size, then it as offered by the mills As a comparison, I just quoted a package using green sand molds, and a 75 pc prototype run of a part very similar to what you have posted, around 4 grand. If you can build a prototype from wood, and it fits and has the form you wish, it can be reverse engineered in a couple of hours. Give me the coordinates of the holes and I can create a model in cad of that part in around an hour. Another example, we built a set of roller rocker arms for an Allison aircraft engine a few weeks ago. I think we got $250 a piece for them including material, I would have to check the job folder to find out exactly what we got for them. They involved 4 different setups, your part would be two at the most. We figure a minimum of $60 for setups. On the rocker arms, the 4 setup charges are amortized over the run
There are plenty of CNC and manual guys on the board who can help you with design and completion of these parts. PERSONALLY, I only like bronze when I want it to wear instead of steel.........but I am NOT a metal person at all. Check out the Chipmakers group on the HAMB, they seem to be into this stuff and can probably help you make it.
I like 4340 for anything that has to be heat treated, just a personal preference since I use it often enough. The others would be fine, I've used 4142 quite a bit as well. I would reverse engineer those parts and do a 2D Autocad drawing or someone with better CAD resources and skills could model it in CATIA or ProE just as fast. Just avoid sharp corners, they cause stress areas and can be prone to failure. It heat treats well, in the "as supplied" form it'll be a Rc 35 (Rockwell harness on the C scale). I'd suggest a hardening between 1475-1525 F and a warm oil quench, followed by an annealing at 700 F to get it down to around a Rc 48. This will make for a tough part. Bob
You may have something there with the wear characteristics of bronze. I was looking at the part from a strength standpoint. Don't order that alloy steel yet! Check this link, this is probably the best material to go with. I use their Ampco 45 and 630 alloys for bushings, but the 863 alloy is probably the way to go. http://www.ampcometal.com/en/index.php?page=a863 Bob
We use a lot of amp940 for one of our weld fixture customers. Its tough stuff, but I think the 4340 is a better choice in this application due to its exceptional mechanical properties. Gwhite has mentioned that there are no moving parts in this assembly. He also mentioned that it had a bushing of some sort in it. If I am misunderstanding him, then there may well be a better material choice than an alloy steel. If there are no wear issues, and there is a replaceable bushing in the assembly, then the heat treated 4340 nearly doubles the bronze's mechanical properties and may be the better choice in this use. But I'll leave that to the Engineers. I just wear the hat. Here are a couple of links for anyone interested in having a look. Ampco 863 http://www.ampcometal.com/common/datasheets/us/A863_E_US.pdf Ampco 940 http://www.ampcometal.com/common/datasheets/us/A940_EX_E_US.pdf 4340, annealed and normalized http://www.substech.com/dokuwiki/doku.php?id=alloy_steel_sae_4340
I think you need to look at the time frame of the speedster construction to understand the material choice of Magnesse bronze. During the 19teens and early 20's. The speed parts manufacturers were not real big operations. Nobody was fabricating by welding flats and angles together. Casting was the way to produce parts. And during this time period, the indoor plumbing and central heating industries were really big. Lots of casting going on for plumbing fixtures and valves and heating equipment valving, too. So you want a hundred castings made to sell to guys converting Model T's to speedsters? You build a pattern, take it to the shop thats running bronze valve castings. talk to the forman, make a deal, he squeezes your patterns in and next week you got a box of parts. You take the parts to work with you at the machine shop you work at and during lunch, you do a couple of parts, every day. Your now a speed parts supplier. There were bigger companies doing this, too. I've read about Laurel Motors who built a lot of componants for the speedster conversions. But I'd bet a lot of this business was very local and the parts sold at the auto parts store or local Ford dealer.
Bronze is sometimes used for low strength parts because it is easier to get good castings with it compared to iron or steel.
I am an Engineer (major in Manufacturing, double minor in Mechanical and Automotive). I like the Ampco products above or an equivalent made by someone else. In their made from wrought (bar, rod stock) material state, the strength will surpass the OEM piece the car came with. I would have to see the part as-installed to make a better decision, but the Ampco material is at least as good as what the car came with and it machines well plus there is no heat treat required. Bob
Fearnoevo & Bob, Appreciate the help. Here's what the brackets look like mounted up. (You're looking at the bracket that goes under the axle and between the spring perch and the wishbone). As I said, they originally used a bushing in the spring perch 'hole'...but I don't know if that was just a precaution that was made due to the material involved....I'm completely open to suggestion on material & construction details. Thanks
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