Hello guys, I've got a quick question for you.I've got a clutch fork that has broken several times due to an extra stiff pressure plate (Not the same fork. I am currently on fork number 3, but they all break at the same place). It always breaks off one or both of the little feet around the throwout bearing. The fork itself is cast Iron.Is there any way of heat treating it, or welding to the backside of the feet to make the stronger? I was thinking about heating the work up until its dull red, then reinforcing them with some nickle rod beads on the sides and back of the feet. The problem might be that the cast is to brittle, and the feet snap...so maybe I need to aneal the feet?What say you?Sometime in the near future, I plan on making a fork out of plate steel, but for now, I need a car to drive. Any helpful hints would be GREAT! Thanks so much!
Reply:i'm not aware of any way to heattreat or aneal the cast iron. if there is room to make the forks wider or thicker,the nickel should help a bunch. a hydraulic throw-out bearing might be a better way to go.
Reply:What make and year vehicle are you talking about? Not that it should be important to the answer, but I'm curious anyway.I would expect any auto manufacturer to have access to better engineers and metallurgists, better testing and processing facilities then most of us do, so if the original parts are repeatably failing, either they are being used improperly or were designed poorly and likely can't be improved by home made heat treating. Do you even have an idea of the metal composition or the h.t. processes it requires? What controlled systems for heat treating do you have? A homemade steel part might be the best solution.
Reply:Hmmmmm having had a bunch of cars most of them Hot-Rods I never really heard of such a thing? if it is an ongoing problem why not switch to a different size clutch and pressure plate (More area less spring pressure) What your describing isn't something you can fix with heat treating or welding beads...... Miller Dynasty 350Twenty Six HammersThree Crow BarsBig Rock
Reply:Its a Porsche 944. The pressure plate is not stock. Its a very stiff aftermarket unit used to hold 450+HP out of a 2.5L 4 cylinder engine.Stock, there is no problems with the fork...so there is no recall, or "fix" for it. Just the pressure plate I have (Which I hate, but can't afford the $600 for another one). The fork is cast, but other than that, I don't know. I have a torch for preheating, but nothing really to monitor or maintain even heat. Should I just preheat to a dull red, then beef up the legs with some cast rod?Like I said, I do plan on making one out of steel, but I would like to fix this one for the time being.Thanks a LOT for the replys. Keep em' coming!
Reply:Originally Posted by m73m95Its a Porsche 944. The pressure plate is not stock. Its a very stiff aftermarket unit used to hold 450+HP out of a 2.5L 4 cylinder engine.Stock, there is no problems with the fork...so there is no recall, or "fix" for it. Just the pressure plate I have (Which I hate, but can't afford the $600 for another one). The fork is cast, but other than that, I don't know. I have a torch for preheating, but nothing really to monitor or maintain even heat. Should I just preheat to a dull red, then beef up the legs with some cast rod?Like I said, I do plan on making one out of steel, but I would like to fix this one for the time being.Thanks a LOT for the replys. Keep em' coming!
Reply:In my travels heat treating should be done by people that do that stuff for a living and not just heat the part up with a torch.......If you really serious about heat treating that arm to make it stronger take it to a pro that has a digital oven and some experience... Miller Dynasty 350Twenty Six HammersThree Crow BarsBig Rock
Reply:I think I'd cryo' it.
Reply:Here you go...This isn't a common problem, so the only "fix" that exists is getting a new fork...This one needs fixed, just to it lasts for a few months until I can weld up a solid one from steel.
Reply:AFAIK cast can't be annealed other than a weld on it, there is a maleable cast iron but your best bet would be to make one out of mild steel like you mentioned.Leo
Reply:Are you sure that's a casting and not a forging? The failure looks too ductile for most castings. It's also cheaply machined . . . sharp edges and a rough finish. You could make a significant improvement in it's fatigue life by rounding the edges, and polishing with a sanding roll. If it's a forging, see if you can find someone to check the hardness. Failing that, test is with a file. Many times, the wear surfaces are induction hardened for wear resistance. If it's soft, (after polishing) have it carburized and hardened .030 deep, Rc 32. That will increase the strength and leave a compressive stress on the surface.Finally, if you fabricate one from mild steel, the design will need to be improved. The yield strength of many cast alloys is every bit as good as cold-rolled steel . . . 45 ksi . . . and much better than hot-rolled.-jimDynasty 300DXSmith He/Ar gas mixerMM350PHobart Handler 120Smith LW7, MW5, AW1A
Reply:Originally Posted by 4sfedAre you sure that's a casting and not a forging? The failure looks too ductile for most castings.
Reply:if that was mine id squeeze it together and tig it, having nothing to lose......
Reply:The trim lines on the side are the last operation of forging. Operating at elevated temperatures requires alloy (carbon steel starts to weaken at 300° F). My guess is it's similar to forged rod material.Easing the sharp edges and shot peening will give you all the part can give. I wouldn't weld on it if it were mine, even if it was off road (loose stuff inside the bell housing sucks rocks).Matt
Reply:seems like your big HP Porsche guys would have worked this out by now, what does everyone else do? Miller Dynasty 350Twenty Six HammersThree Crow BarsBig Rock
Reply:A quick search on google says not only is the clutch fork an issue - it could break and it could also wear down, but, more importantly the concensus is its cast steel - which should means its a lower carbon that cast iron which should also mean its weldable.Judging from the complaints, you might want to consider wear facing it as well. Basically putting a hard face on the side the wears the most. If you screw it up, looks like you can get another one pretty cheap on Ebay and the like.So... order a new one and try to weld up the old one. After welding, you might need to re-machine things to get everything to line up.I would hit one of the stick welding books and lookup rods for cast steel. MG (http://www.messerwelding.com/)or UTP()They have gazillion different rods for various flavors of cast iron both with and without pre-heat etc.BTW, from that picture, the wide parting line also leads me to believe its not cast iron. True castings are done in molds and the parting line from the molds is typically much thinner. When the piece is pounded into shape, the dies don't come all the way together and thus leave a wider parting line (and maybe grinding marks on it)One other thing you can consider, convert to hydraulic clutch. See if tilton makes a throwout bearing for it. While you are at it, get one of tilton dual master cylinder + clutch cylinder pedals and ditch the power brakes.Con Fuse!Miller Dynasty 350Millermatic 350P-Spoolmatic 30AMiller Multimatic 200Hypertherm PowerMax 1000G3Miller Maxstar 200DX
Reply:Two for sale right now on Ebay. One is $30.. and one is $49. A new one is $315.00 !!Here is a good article on the subject:http://www.pelicanparts.com/techarti...ster_slave.htmWhat I would do is buy that $30 dollar one (right now), and beef it out with some TIG ER80 S2 filler wire around that weak area. Let it cool slowly. Then I would smooth the rough edges. IT is a hydraulic actuated arm. There were problems with the hydraulic cylinder mounts tearing too.I would do some diggin around on the internet for a high peformance solution.More on the mess-http://forums.rennlist.com/rennforums/924-931-944-951-968-forum/82363-what-is-up-with-the-944-clutch-forks.htmlBut there may be a clue here why it breaks. It goes from being rounded to being flat where it contacts and maybe that is why it breaks?Last edited by Donald Branscom; 03-10-2011 at 05:56 PM.AWS certified welding inspectorAWS certified welder
Reply:Two for sale right now on Ebay. One is $30.. and one is $49. A new one costs $315.00Here is a good article on the subject:http://www.pelicanparts.com/techarti...ster_slave.htmWhat I would do is buy that $30 dollar one (RIGHT NOW if its good.) and beef it out with some TIG ER80 S2 filler wire around that weak area.. Then I would smooth the rough edges. IT is a hydraulic actuated arm. There were problems with the hydraulic cylinder mounts tearing too.I would do some diggin around on the internet for a high peformance solution.More HERE http://forums.rennlist.com/rennforum...tch-forks.htmlIn the article it says the rounded part that contacts gets rounded to flat and then it breaks?Maybe that pressure plate is no good.It all needs a complete check up.Last edited by Donald Branscom; 03-10-2011 at 06:01 PM.AWS certified welding inspectorAWS certified welder
Reply:Very good answers!! Thank you a ton!I will agree that it is probably forged. I hadn't considered that, so I never really thought about it. I'm also a member of both Pelican, and Rennlist. This really isn't a common problem because of the pressure plate I use. Its not 1 step better than the stock plate, its about 4 steps better. I made a mistake in ordering it. Nobody uses this pressure plate (Honestly, maybe only 4 or 5 of us). It is ridiculously stiff. Sitting at a red light for more than a few seconds, and my whole leg hurts. So, with it now being forged, is it safe to fix this with some 7018, then grid off the edges? I am still going to make a new fork, but I want this one back in this weekend. Sounds like a ton of work to do more than once, I know, but it is what it is for right now. It actually only takes me a few hours to pull the transmission back far enough to get the fork out. My goal isn't to keep Ebay suppliers of clutch forks in business . Hopefully when I get one made up (Thicker and beefier), it will be the last time.Last edited by m73m95; 03-10-2011 at 09:03 PM.
Reply:Just for some help it is a BAD habit to hold the pedal in while at a light....get used to popping it out of gear at a light..........it's hard on the throw-out bearing, main bearing thrust surfaces, and as you already know your leg......... Miller Dynasty 350Twenty Six HammersThree Crow BarsBig Rock
Reply:Have you considered putting weaker springs in the pressure plate assembly? They are probably a standard size or close to it. Century Spring stocks just about anything you'd need.
Reply:Oh yeah I forgot we use flyweights on our slipper clutches just for the reason you can control the pack pressure by adding or subtracting weigh from the fingers = Less spring pressure you should think about it.......It works Miller Dynasty 350Twenty Six HammersThree Crow BarsBig Rock
Reply:Originally Posted by m73m95Sitting at a red light for more than a few seconds, and my whole leg hurts.
Reply:that's a bunch of HP for a small dia. clutch (assuming it is less than 10 in") I would incorporate flyweights myself and get rid of that hard pedal......that sucks...... Miller Dynasty 350Twenty Six HammersThree Crow BarsBig Rock
Reply:But is 7018 ok? lolm73,You're going to be "hard pressed" to do anything to make forged steel any stronger.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:This guy just likes pulling the tranny out........LMAO.....What's the term? Oh yeah you can lead a horse to water but................... Miller Dynasty 350Twenty Six HammersThree Crow BarsBig Rock
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OL, its not that I LIKE pulling the tranny out, its that I don't have a choice right now. I used some 7018 to beef it up, all the way around both legs. It'll be back together later tonight. If it gets me some time to make up another fork, or find a stronger one, then that will be good enough.Like I said, this is the second one, and I don't want to just keep buying forks off of ebay. This is a temporary solution, until I can find a permanent one. Thank you all for the help though. I don't post often (as you can see), but I do read a lot. This is a great forum.
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et us know how this works out m73.With 7018 you probably have a fair undermatch, minimum materials for forging would be 1026-1030 with mechanicals in the 100ksi range (about 220 brinell hardness). More commonly 1030 is thermal treated to 250-270 brinell which works out to 125-130ksi tensile.This would be considered "junk" in the world of forged parts.Consider that a little alloy or carbon lets the part go way up from the above. 1045 and 4130 forgings are common in the 310-320 brinell range (150ksi tensile) and 4340 is common from 360-390 brinell (170-180ksi tensile).Add to that, anything with .3 carbon and above is going to have some direct hardening potential and should at least be post heated. The higher the carbon or CE the more need for thermal treatment.From the above, with 7018, the section should be increased in size from 2 to 3 times to give equal stength at room temperature. If the part were alloy running at elevated temps the section size needs to increase more to resist "creep".Just a liitle dry, boring data to look at.Matt
Reply:That is a good post!! ^^^ I did make the leg thicker, probably double the size. Also rounded the edges, and post heated, then wrapped in a fire blanket to cool more slowly. It should be ready to go tomorrow, and I'll let you know how it goes.
Reply:Vee it out and weld it back together. 7018 is likely going to be the best bet for a hobbyist. I would either build up some weld on it or reinforce it with some steel, both sides of each fork, and as much as possible in the hollowed out portion as clearance of the throwout bearing will allow.
Reply:Originally Posted by B_CJust for some help it is a BAD habit to hold the pedal in while at a light....get used to popping it out of gear at a light..........it's hard on the throw-out bearing, main bearing thrust surfaces, and as you already know your leg.........
Reply:Buy correct pressure plate before you trash thrust bearings on crankshaft!!!!!!!!!!!!! It is not if, its when!!!!
Reply:Still holding strong...
Reply:could have used 10018 (100k) and been atleast close to the original forging strength using preheat and post heatLast edited by WeldorWes; 03-16-2011 at 05:29 AM.Miller Xmt 350Lincoln Ln-25Ahp 200xSmith Gas Mixer AR/HTig is my Kung FuThrowing down dimes and weaving aboutInstagram http://instagram.com/
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