Guest Anonymous Posted November 16, 2001 Share Posted November 16, 2001 So what do you guys say to this... Why not fab the JTR tranny mount out of Aluminum instead of Steel? Sounds like an easy way to shave off 10-12lbs of weight from the car. Hell, people pay $200+ for a gear reduction starter to save that much weight. Aluminum also has the advantage of being easier to machine. Now is Aluminum's inferior fatigue strength the problem here? I don't see why, considering the vibrations involved are of a relatively low amplitude. What about strength concerns? Would an Aluminum mount be able to withstand the heft and torque of an SBC+Tranny at full steam? What if we were to make it out of 1/2" stock instead of 3/8"? Quote Link to comment Share on other sites More sharing options...
Tim240z Posted November 16, 2001 Share Posted November 16, 2001 I don't really like the JTR design anyway, which is why I made mine to attach to the tunnel intead of the floor. I would imagine that the one I made is also significantly lighter the hunk of steel which JTR sells, and I think that the adjustabilty is better for driveshaft angle. I think that making one similar to the JTR one, but out of rectangular Al tubing would be better than the JTR one, but then you would need to be able to weld alley, or be able to bend the tubing.IMHO. Tim Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 16, 2001 Share Posted November 16, 2001 Yeah the JTR unit might not be the prettiest, but its simple and easy to fab. Your mount looks nice Tim, but I would imagine it would take more time to make, not to mention a welder. Plus the JTR mount can be made to be adjustable with the right spacers... I am lucky enough to have access to a well equipped machine shop, however I have not used the tubing bender yet (can't be that hard) There shouldn't be any difference between bending Al or Steel right? So it looks like I'll be going ahead with the Al tranny mount to shave some weight unless any of you guys give me a good reason not to. I mean there has to be some catch otherwise Mike Knell would have recommended it himself... While I'm on this flight of fantasy, why not fab the setback plates out of Aluminum while I'm at it? Or would the shearing loads be too great? That's a pretty gruesome thought, having the engine shear off the plates at 75+mph Again, we could make em out of thicker material, and compensate by having thinner spacers, saving another 10-15lbs. Or have I taken this weight reduction "fetish" too far? Quote Link to comment Share on other sites More sharing options...
Tim240z Posted November 16, 2001 Share Posted November 16, 2001 I think the cost/effort factor for the gains would be unbalanced. If you wanted to lighten things, I would be more comfortable with drilling some holes in the steel setback plates rather than go Al. With the vibrations and heating and cooling I'm not sure if the Al would hold up, but I'm not a metallurgist either. Tim Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 16, 2001 Share Posted November 16, 2001 Guess I'm gonna have to bust out the Materials Science book... Which isn't to say I've got a clue about what I'm talking about But hopefully somebody else does and can expound on the matter. Gentlemen? Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 16, 2001 Share Posted November 16, 2001 I'm not sure, Aluminum to be as strong as steel generally has to be magnitudes larger in cross section (granted it could be hollow if the thickness is right) to be as strong. I suppose an Al crossmember is possible, could use aluminum motor plates and rear mount and rubber mount the ends I suppose too. I will tell you, if you use the JTR cantalevered motor mounts, that alot more weight goes back there than you might expect. First time you let the weight off the rear of the tranny and it puts weight on that crossmember, it'll make a believer out of you. I went ahead and used the JTR piece and even it noticably deflects under the weight. IMHO, there are better places to take weight out, the tranny mount is low and in the middle of the car. Aluminum heads, water pump and move the battery behind the seats will do far more good than 10-20 lbs in the middle of the car and down low. Just an opinion though, heck if you have the resources and the design to do it, go for it, love to see it! Regards, Lone Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 16, 2001 Share Posted November 16, 2001 So can anyone give me a ballpark estimate on what the weight distribution of the engine/tranny is? i.e. how much weight is on the front mounts vs. how much is on the tranny Xmember? The whole assembly should weigh between 590lbs and 740lbs depending on what tranny you're running, and how much aluminum (read $$) you've got in that engine. Hopefully, I'm planning to be on the lighter end of things. Anyhow, if I were to fabricate the X-member out of 1/2" Aluminum, that should make it 137% stiffer than if I made it out of 3/8", and should more than compensate for the difference in strength between the two (between 50-60% I think) Besides, I can get 1/2" Aluminum stock more readily around here, and it would save me the trouble of having to mill it all down to 3/8" Again, I don't have my engineering books handy right now, but I will calculate the theoretical deflection of the X-member to get a feel for how much flex we are looking at here. And Lone, there is nothing better than a FREE weight reduction Aluminum heads, water pump, etc.. cost money (which isn't to say I'm not gonna splurge on them... As you can Z, I'm a weight freak ) And its not like we're required to run a minimum weight, so I might as well get those aluminum heads AND have a lighter X-member... What do I have to lose? Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 16, 2001 Share Posted November 16, 2001 Nothing, carry on man, carry on! Regards, Lone Quote Link to comment Share on other sites More sharing options...
ZROSSA Posted November 16, 2001 Share Posted November 16, 2001 Got to agree with you there Omar. Dont know much about the differnt properties but i do know that my all. mountain bike is a hell of a lot stiffer then a steel one for a tiny bit less weight. You might have to fab the mounts so that there is extra metal where you get bending loads. Let us know how you get on. Douglas Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted November 17, 2001 Share Posted November 17, 2001 Bike stiffer? Is the frame members in compression or what? In this case the trans will be attempting to bend the support and twist it not compress it so comparing it to the bike might not be applicable. The bike frame I had was pretty stiff too but it was fairly big tubing and before I was done with it I had cracks in several places I broke pedals (cro moly), handlebars (aluminum), goosnecks (cro moly), seat shafts (fluted aluminum), wheels (plastic?!), oh and a few cranks were bent which were both aluminum and cro moly. Not sure bike parts are going to apply Stiff and strength in this case might be two different things. Lay a bike on it's side on a curb and jump on the tubing - you may see what I mean... Done correctly I think an aluminum mount would work. However I'd NOT use just flat plate like JTR did. I'd make a T out of it. Flat plate and then weld a section under it to strengthen it? Tubing sounds tempting but how thick a wall can you get that in easily? Lone's right though - the JTR mount is pretty beefy and there may be a reason for it. I had to section mine and it required a nasty chop saw to do the work. Beefy! Quote Link to comment Share on other sites More sharing options...
Dan Juday Posted November 17, 2001 Share Posted November 17, 2001 Something to keep in mind when bending aluminum is "work hardening". I’m also no metallurgist but I believe this is much more of an issue with aluminum than steel. The aluminum will be harder and more brittle in the areas where it is bent. Is this not why billet aluminum parts are more desirable than bent parts? Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 17, 2001 Share Posted November 17, 2001 To be able to use aluminum you will need to use thick hard grade stock like you would see in a motor plate. The [problem here is that you CANNOT bend aluminum of this strength. It can be welded to make a very nice light weight mount setup. Look in a jegs catalogue and see if you can get a good look at the thickness of a motor plate. I will try to take some measurments and a pic to post form my plate. I would not go with any other grade of aluminum. Iplan to pound on my Muncie four speed and will settle for nothing less than an overbuilt mount setup. Quote Link to comment Share on other sites More sharing options...
Rob Posted November 23, 2001 Share Posted November 23, 2001 Be careful when designing the tranny mount, if you go that way. That mount is not only holding up the weight of the tranny and engine, shared with the motor mounts. It is constantly experiencing shock loading as you drive over bumps. (Ever notice your shift lever bouncing a little over bumps, on any RWD car?) I'm guessing the g loading of going up a hill suddenly at high speed could be quite significant as well, basically making everything heavier. So I am trying to make two points here. 1. Fatigue strength is important for the tranny mount and engine set back plates and steel is much better in this area. 2. If you do design one out of aluminum (I'm not saying its impossible) keep 1. in mind and overdesign the hell out of it to account for shock loading and hills. My guess is that if you do properly design an aluminum mount the weight savings will be less than you think. FYI, I had my fabricated steel mount fail on me due to a bad weld that finally fatigued. I probably spent about as much labor fixing my unibody that literally tore apart due the mount failure than the rest of my conversion. Believe me you don't want this to happen to you! The JTR mount has no welds which is a big plus. My car now has the JTR mount. I did increase the bolt sizes to 5/16, and I recommend reinforcing your floor by welding a sheet metal patch to it to distribute the load between the frame rail and tunnel better. Good luck, whatever you do, and if it helps any I am also a weight freak. When you think about it the thing that makes V8Zs so incredible is the power to weight ratio so we all are to some extent! Quote Link to comment Share on other sites More sharing options...
fl327 Posted November 23, 2001 Share Posted November 23, 2001 go for it, why not. but its not like the z v8 swap lacks any power to weight in the first place, the extra ten to twelve lbs you may save can be made up in other ways, like the jtr says. Quote Link to comment Share on other sites More sharing options...
Guest Jeff Rimmer Posted November 23, 2001 Share Posted November 23, 2001 Well, This is an excellent static/dynamic and strength of materials problem! If you want to be dead on. If you know the power of your engine you can calculate its moment, and apply its forces to the set back plates and the tranny mount. If you know how to use CATEA, it can do most of the calculations for you, and calculate the stress/strain on the part of the plate. A nice little program. I would be immensly concerned with the use of aluminum. Especially in the engine bay. The heat applied to the set bach plates may pose a problem. However, if you design it properly with gussets and the like, you will succeed. However, to gain the strength you need, you will most likely not save all that much weight. Not to mention the hassle of working with aluminum and the extra room it will take, though that my not be a concern for your particular setup. But I am biast, being accustomed to designing for and working with 316L stainless non-stop. Goodluck! Rim Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 24, 2001 Share Posted November 24, 2001 Check this out, you may find this interesting http://epics.aps.anl.gov/asd/me/ElasticBeam.html Pretty handy isn't it? Please correct me if I'm wrong on any of this E for aluminum is 70 x 10^9 GPa steel is 200 x 10^9 GPa I in this case would be 1/3 bh^3 where b= width of the beam (in meters) and h= thickness (again in meters) L is the length of the beam between the mounting bolts Finally, P is the load in Newtons (mass in kilograms x 9.8) Let us use a safety factor of 5 to account for shock loading, G-forces, etc.. Now the mass on the X-member should be something on the order of 350lbs (lets be generous) which is 160kg so P is around 1550 or 7750 with the safety factor. Finally, we select scenario 4 as it most closely resembles the loading the Xmember is experiencing Given this info, we can calculate the maximum deflection, however it is only an approximation given that P in reality isn't a point loading, but is distributed over a span of 3 inches or so around the middle, and that we aren't dealing with a flat beam. Furthermore, E would be reduced (by how much, I do not know) due to the work hardening caused by bending the aluminum. This is partly made up for by the fact that the vertical, or angled sections of the beam will be less prone to deflection than the flat horizontal bits. What none of this takes into account though, is the fatigue strength of Aluminum. I am inclined to believe that the vibrations incurred over the Xmember's useful life are of an insufficient amplitude to be a cause for concern. Consider an aluminum flywheel for example. Of course I could be wrong, very wrong, with disastrous consequences. What do you guys think? Quote Link to comment Share on other sites More sharing options...
Miles Posted November 24, 2001 Share Posted November 24, 2001 Just a thought. Have you considered the MSA tranny mount? It bolts up inside of the tunnel and does not weigh much. Very easy to install and it allows a lot of flexibility in adjusting the tail shaft angle. MSA sells the tranny mount with their v8 conversion kit. You may be able to buy the tranny mount separately. You can contact MSA at 800-633-6331, 714-639-2620, www.zcarparts.com. Very simple to install and it's solid. MSA also sells the tranny rubber mount as part of their conversion kit. The rubber mount is designed for the 700r auto trans, but it worked fine for my T5 install. Cheers Quote Link to comment Share on other sites More sharing options...
GoodGuyGary Posted November 24, 2001 Share Posted November 24, 2001 What grade of steel JTR use? The strenght of the the steels are varied. There is a kind 17-4 PH is 3 times as strong as 316 and which is much stronger then carbon steel(WCB if you know what it is). I really want to know what JTR use, then I can pick something which will be stronger and lighter than them. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 24, 2001 Share Posted November 24, 2001 It looks like plain ordinary mild steel to me (jtr mount). Strength isn't a problem with they're mount . As I mentioned earlier, theres better weight reduction possible in other ways, and ones that won't have the chance of dropping an expensive transmission on the ground at speed. Trust me (or don't , find a hydridz member and get a ride in one) when I say 5 - 10 lbs here or there (I know they can add up, but if your prudent) isn't going to lessen the grin on your face one bit. Just an opinion of course. Regards, Lone Quote Link to comment Share on other sites More sharing options...
Ray Posted November 24, 2001 Share Posted November 24, 2001 Why not make a boxed mount out of steel sheet.. Alot of the stock stuff if two steel stampings welded together. Why not duplicate something like that... I like the idea of it locating in the tunnel... You could also make it out of flat aluminum, and build mounting pads in the tunnel... just a thought.. Quote Link to comment Share on other sites More sharing options...
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