BlackBeaut Posted June 3, 2005 Author Share Posted June 3, 2005 I think what you've got there is way overkill, and I don't think it would hurt to remove the green link. Remember the initial structure was 2 4" wide pieces of 1/8" plate attached by 4 bolts and now you have these massive ribbed aluminum pieces that tie into the mustache bar bolts. The only downside I can see to this design is that it's going to take a lot of material and a lot of milling. Yep I totally agree, excess material has been playing on my mind. I've been thinking that (looking at the above design) it could be split into 4 pieces. Main upright, moustache bar mounting bolt end and 2 struts between them. All bolted together would give in effect the same over all structure but without so much waste material. I'm not sure about removing the green link. Without it they'd be nothing tying the bottom of the uprights solidly together (the mini bar is bushed), they'd be relying on the bolts at the top for rigidity. OK I realise that they should be pretty damn rigid but why spoil the ship for a ha'porth of tar?! Perhaps ditching the green bar but linking the two lower bush caps would be a simpler approach. Cheers, Rob Quote Link to comment Share on other sites More sharing options...
JMortensen Posted June 3, 2005 Share Posted June 3, 2005 Perhaps ditching the green bar but linking the two lower bush caps would be a simpler approach. Then you wouldn't be able to use your snazzy toe adjuster. Keep the green bar if it makes you feel like it's braced better, I just think that with the rest of the structure being so massive it wouldn't matter. Quote Link to comment Share on other sites More sharing options...
BlackBeaut Posted June 3, 2005 Author Share Posted June 3, 2005 Then you wouldn't be able to use your snazzy toe adjuster. That's true but it was never my intention to have toe adjustment at this end. How about this though for complete simplicity? 30mm steel tube and a few bits of fat pipe all welded up and ready to go. Lacks blinginess of machined ali but it could always be chrome plated Now if I could just learn to weld I'd probably be able to make that myself. Cheers, Rob Quote Link to comment Share on other sites More sharing options...
TimZ Posted June 4, 2005 Share Posted June 4, 2005 Quick update - I just replaced the giant pic a few posts back with a much better one (more palatably sized), showing the relationship between the moustache bar and the uprights. I did some measurements, and it appears that the dimension between the front face of the m-bar and the rear face of the uprights (plane intersecting) is about 10mm. I got this dimension by making a few measurements relative to the crossbar on cradle, so I'd give it maybe +- 1mm in accuracy (if I'm lucky ). Quote Link to comment Share on other sites More sharing options...
BlackBeaut Posted June 4, 2005 Author Share Posted June 4, 2005 Thanks Tim, that's really helpful. Looks like my measurements aren't too far off the mark at all. I think I've seen the light though and will make something up from square section steel tube, cost and ease of production just have it all going for it. I've also realised that my cunning mini bar location has screwed up the front diff mount top runners so I'll have to go with something underneath the diff like you did. Think I'm pretty happy with the way this is all turning out, definitely like to thank everyone for their contributions and helping get my thoughts straight on this. I should end up with a really robust rear end that should last!! Cheers, Rob Quote Link to comment Share on other sites More sharing options...
Guest 240zJake Posted June 5, 2005 Share Posted June 5, 2005 Said someting about needing a CAD program, well I have never used the software or the site but it is a really cool concept and the software to draw the stuff is free http://www.emachineshop.com/ Quote Link to comment Share on other sites More sharing options...
TimZ Posted June 5, 2005 Share Posted June 5, 2005 Thanks Tim, that's really helpful. Looks like my measurements aren't too far off the mark at all. Just keep in mind that my measurements wen't exactly the same as your mystery dimension - I modded your original pic to better illustrate what I was measuring: Also, one issue I see with this latest design is ground clearance - I would humbly suggest mounting the lower cradle outboard of and next to the lower bushing caps - remember you will still want to pass your exhaust under that rear crossbar. Quote Link to comment Share on other sites More sharing options...
BlackBeaut Posted June 5, 2005 Author Share Posted June 5, 2005 Also, one issue I see with this latest design is ground clearance - I would humbly suggest mounting the lower cradle outboard of and next to the lower bushing caps - remember you will still want to pass your exhaust under that rear crossbar. No need to be humble!!!! I agree, I just sort of bunged them in the model for a rough idea. I'm also not sure that I'll bother with the rear lower cross link. I think I'll just use one long piece along the top rather than having two separate uprights. Now I know all the critical dimensions (thanks again) I can figure out all the little details. Cheers, Rob Quote Link to comment Share on other sites More sharing options...
S15 200sx owner Posted June 6, 2005 Share Posted June 6, 2005 S15.... Just a quick non related question. What size are the rims on your car at the moment? Douglas Hey ZROSSA, my current wheels are the NZ made Euro 5 spokes 16x7's all round, i'm gunna need bigger than that mate Quote Link to comment Share on other sites More sharing options...
S15 200sx owner Posted June 6, 2005 Share Posted June 6, 2005 Thanks Tim' date=' that's really helpful. Looks like my measurements aren't too far off the mark at all. I think I've seen the light though and will make something up from square section steel tube, cost and ease of production just have it all going for it. I've also realised that my cunning mini bar location has screwed up the front diff mount top runners so I'll have to go with something underneath the diff like you did. Think I'm pretty happy with the way this is all turning out, definitely like to thank everyone for their contributions and helping get my thoughts straight on this. I should end up with a really robust rear end that should last!! [center'] [/center] Cheers, Rob I am really liking the look of this latest design, as i too would be able to build this myself! Great work with that CAD programe Rob, very inspiring indeed, Please keep us informed with your progress on the design and build of this cradle, This thread should be set in concrete!!! I will sure be having a crack at making up something along this design! Cheers. Quote Link to comment Share on other sites More sharing options...
BlackBeaut Posted June 6, 2005 Author Share Posted June 6, 2005 Thought I'd measure up the diff so that I can figure out the ground clearance issues with the side rails in my design. I now have a very perplexing situation that can be answered by one simple question. Is the diff installed at an angle to the vertical? If not then I seem to have a prop shaft going straight through the front cross member situation on my hands: This pic shows the diff mounted back in stock location, ignoring my cunning plans to shift it forward. Now it looks like there's room to shift the whole diff up about 30mm but even then things would be tight over the front cross member without lifting the nose slightly. I saw on this website that there was some issues with interference but that was with an R230 which I would've thought would be even tougher to fit: http://www.v8zcar.com/s30z/r230-2.htm Is the pinion shaft in a short R200 lower than in a long R200 for some reason perhaps? Think it's time to get under the car again and check the measurements another couple of dozen times Here's the offending article for reference: You'd've thought after all the effort I went to to clean it up, it would've had the decency to just fit right!!! Cheers, Rob Quote Link to comment Share on other sites More sharing options...
TimZ Posted June 6, 2005 Share Posted June 6, 2005 I think my r230 does angle up a bit - I've got maybe 4mm clearance above the crossmember. I have my m-bar bushings cut down a fair aount to allow raising the rear of the diff a bit - there is only about 3mm of bushing above the m-bar. Also, you can sort of see in this pic that the mounting point for the front ears is about 1" (sorry to mix units ) higher than the control arm bushing centerline. I think my r230 is coming out considerably higher in the rear than what you show, since I still have sufficient clearance between those gigantic 6 bolt side flanges and the control arms (although I did have to trim them a bit). Quote Link to comment Share on other sites More sharing options...
BlackBeaut Posted June 6, 2005 Author Share Posted June 6, 2005 Hallelujah!! Votes are still being counted on whether I'm insane or not but at least I'm back on my own windy little track!! Thanks Tim!!! So in this pic I've raised the rear by 15mm which is what I get if I measure the height of the poly moustache bar bushing flange and washer and deduct 3mm. I've positioned a mounting point so that it's 1" (what's 25.4mm between friends?!! ) above LCA centre line and allowed and extra 7mm for a bushing flange (red bit). That puts the diff nose up at about 1.5 degrees which with an 80mm diameter propshaft should just clear the cross member. I think I'm going to take advantage of my extra space and raise it a little bit more. Hmmm, also need to redesign my minibar to get things back in stock-ish location Cheers, Rob Quote Link to comment Share on other sites More sharing options...
Guest fsae_alum Posted June 7, 2005 Share Posted June 7, 2005 Ok...I'm new here...but not to machining, Aluminum, or sports cars. If you are planning on doing any serious cornering or launching with your car, I would seriously consider using steel instead of Aluminum. As you mentioned, Aluminum has a big problem with Fatigue. It also has a problem with oxidation that can fortunately be treated with annodizing (red would be nice). If you do choose to use Aluminum, I'd probably prefer to use 6061-T6 instead of a 7000 series. Yes.....7000 series is very strong, BUT it is also VERY prone to crack propagation. I did a TON of researh on this in the past and learned the hard way. I would feel much more comfortable using mild steel (heat treated after being Tig welded of course). Just something to chew on from a mechanical engineer. BTW...I love what you guys are doing by trying to just build it yourself and make it better. I can't wait to get my Z and go though the same trials and tribulations!!! Quote Link to comment Share on other sites More sharing options...
BlackBeaut Posted June 7, 2005 Author Share Posted June 7, 2005 I think you're absolutely right about the use of Alumini(u)m It's one of those materials that I always want to use because of it's 'good' properties but I always seem to end up with good old mild steel because of it's (ali) bad properties. Using steel will also mean that this project will be well within the capabilities of anyone who can weld to an acceptable level (worryingly that doesn't include me!) If I'd gone with the billet design then costs would no doubt have been silly and it could only be produced with CNC equipment putting it right out of the reach of most of us ordinary Joes. Once I'm happy with my design, which will most likely be once it's on the car, I'll post up the plans so that anyone can attempt it. In the meantime if anyone wants a rough plan just drop me an email, I've done all the drawing in Illustrator so the art is available in ai, eps vector files or pretty much any bitmap format you'd want. I have to say that even though my Z is (turning out to be) a bit of a mess, I'm really loving it as it's allowing me to experiment and stretch my mind a little which is something I would never have considered doing on my previous motors. It's nice to dust of the grey cells now and again and get them to do a bit of work Cheers, Rob Quote Link to comment Share on other sites More sharing options...
Hugh Posted June 11, 2005 Share Posted June 11, 2005 I'm looking at all this planning and all this work you're talking about here... and I'm seeing all these bushings. If you're going to overkill the strength of the piece, why put in any bushings at all?? When I had the R230 mounted in my old 180sx, I didn't have any bushings whatsoever. I mounted it solid to the subframe. My subframe was hung on Aluminum bushings as well... so there was no play anywhere in the system. This created a bit of diff noise in the car, for sure... but nothing I couldn't tolerate. It was weird for the first couple of days, then it was just normal. (and I grew to like having the sound) My diff had no twist, no play, no binding or wearing out bushings. Application of power (395rwhp SR20) was unbelievably direct and I loved it. This also should help to eliminate any wheel hop (as it did in my old car) Granted, for those who like their cars more timid and user-friendly... going bushing-less might not be a great idea. Quote Link to comment Share on other sites More sharing options...
S15 200sx owner Posted June 12, 2005 Share Posted June 12, 2005 I am thinking the same thing Hugh, I will make up a rear frame but will solid mount the diff, my car is a race car, so not to concerned about the noise. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted June 12, 2005 Share Posted June 12, 2005 Best to solid mount the entire drivetrain if you solid mount any part of it. If not the weakest link in the chain is going to break. If you just use a solid front diff mount on a stock setup that can often times be the front diff crossmember. If you solid mount the diff and the mustache bar then the weak link becomes the driveshaft. You'll chase that weakness all the way up the drivetrain. Solid mount the trans and the trans crossmember is the weak link. Solid mount it all and now all you have to worry about is your bolts vibrating loose. Just MO, but I've talked to people that it has happened to. That being said, you guys are right, solid mount is definitely better for a race car. Rob has said this is for a street car though. Also I wouldn't give up on AL just yet Rob. Look at some more modern cars and there is plenty of aluminum used in high stress areas like control arms and subframes. Quote Link to comment Share on other sites More sharing options...
BlackBeaut Posted June 12, 2005 Author Share Posted June 12, 2005 Hi all, Sorry for not keeping this up to date, erm well that's because not a lot has happened really, got my metal ordered so things should start moving again once that's here. I also think I've got the front diff mount worked out in theory, nicely bushed of course As for bushing things, I agree with all points made but like Jon points out my car will hit the roads and not just the perfectly smooth black top of the track. If you knew how bad the roads are around here you'd be questioning my desire to drive on them in anything other than a farm tractor Cheers, Rob Quote Link to comment Share on other sites More sharing options...
S15 200sx owner Posted June 12, 2005 Share Posted June 12, 2005 I also think I've got the front diff mount worked out in theory' date=' nicely bushed of course Rob[/quote'] Rob, Please do tell Quote Link to comment Share on other sites More sharing options...
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