Billet Ali Rear Subframe

[BlackBeaut]

Hi Tim,

 

Thanks for the comps, can't remember if I said but I managed to get on a weld course at the local tech college which finished a few weeks back so I'm a fair bit more confident waving the mig around, still doesn't mean I'm any good or why some welds come out fine and the next one I do looks pants but never mind

 

Regarding the big holes, yup I've got some inserts that go in. For reasons that seem lost in the mists of time, they're screw in things I made. Its possible I was thinking that leaving the holes open would mean when I get it zinc plated then the inside of the top tube would also get done.

 

Cheers,

Rob

[zguy36]

How much more does this weigh than the stock setup? It looks really beefy/overbuilt

[JMortensen]

I bet the mustache bar and this subframe weigh about the same. Rob, that thing is REALLY impressive. It's coming together very nicely, congratulations.

[BlackBeaut]

I so don't want to weigh it!! It's definitely hefty, getting it into place under the car makes me regret not going anywhere near a gym for too many years, but it sure won't take no sh*t from nobody! At least it's sprung mass anyway!

 

Here's a rough idea of an overhead frame connecting to Ron Tyler type mount, that should fit in the available space - man Datsun could've been a bit more generous under there Angles and general dimensions definitely to be taken with a pinch of salt!

Obviously it's missing a vital connection between frame and front of the diff but like how hard can that be :D

 

Cheers,

Rob

[j260z]

very nice work! i like the diff isolation idea.

[Owen]

Awesome work Rob!

 

Interesting, my front diff mount that I made 3 or so years ago is similar to the grey part in your picture. Except it isn't tied in to the rear. I haven't seen Mr. Tyler's mount but am interested.

 

Mine has two plates going back instead of the tubes you have, and they have horizontally mounted fins with holes in them which line up to the diff mount holes. It kinda looks like a fighter jet But basically, it's just suspended there, no mounting from underneath so the bracing to the rear would help a lot.

 

What are you doing for the front of the control arms? Are you using the stock x-member? I did away with that by cutting it and leaving just the "saddles". But I was told that without some bracing, the diff will want to nose dive despite the beefy steel I used in mounting it up top.

Owen

[BlackBeaut]

Hi Owen,

 

I've got the machined cross member to use up front. I had that made up as the original plan was to use a fore-aft pair of bars running underneath the diff to support it from below, like Tims solution, but I'm really liking the idea of isolating the diff fully now. I'll still use the machined front member as it gives more clearance for the prop-shaft and exhaust than the stock member anyway, plus I got it so might as well use the sucker!

 

I remember checking out your front mount back in the day, it's a nice simple solution. For the Ron Tyler mount check this thread:

http://forums.hybridz.org/showthread.php?t=95128

It's primarily designed for the long-nose R200 but as it provides a good mounting solution at the front I'll work up something similar.

 

Cheers,

Rob

[johnc]

One welding tip (although with the thickess of the materials used this tip is not really needed):

 

Weld all the way around two parts being joined. In your picture above of the gussets that are added between the clevis and the center plate where the diff mounts, the welds are not carried all the way around. The gaps at the ends of the gussets are places where cracks can start.

 

Again, in this instance its not relaly an issue. If this part was made of aluminum then those unwelded ends would start cracking.

[johnc]

Also, if you have the dimensions of or would like to build another front diff aluminum crossmember I would be intersted in one almost immediately.

[BlackBeaut]

Hi John,

My cross member is mild steel, rather than ali as it was planned to be welded to. I can send you the plans for it though if you want, then you can get a local shop make one up for you in ali? I suspect it would be a lot cheaper that way then having my local shop make it up and then sending it to the other side of the world

 

Drop me a PM if want the plans.

 

And thanks for the welding tip, I'll slap a bead round there the next time I'm welding.

 

Cheers,

Rob

[TimZ]

Regarding the big holes' date=' yup I've got some inserts that go in. For reasons that seem lost in the mists of time, they're screw in things I made. Its possible I was thinking that leaving the holes open would mean when I get it zinc plated then the inside of the top tube would also get done.[/quote']

 

Just to be clear, I was thinking of the four smaller holes, where the original uprights bolted in.

[BlackBeaut]

Yup, those are the ones Tim. Here's a pic of one of the inserts and one of the studs I made as well. Hand threading a M16 thread is a biatch! Plan is to plate the frame somehow then screw in the insert and over paint it all , probably with POR15 Glisten PC which should do a damn fine job of sticking it in place forever.

 

 

I was reading up on hot zinc galvanising and it seems like frame structures like this need a vent hole in each otherwise sealed tube otherwise they might explode when dropped in the tank of hot zinc - nice, I'd be so happy if that happened after all the work I've put in

 

Cheers,

Rob

[BlackBeaut]

Been thinking about the top frame again. Think I've come up with a decentish idea making use of rod ends to connect things up, which means it should go together and come apart more easily too making installation a bit less of a work out.

 

 

So four rod ends. Two up on the rear frame and two down on a modified Ron Tyler mount.

 

 

Then a cunning frame work connects them which the front of the diff can be connected to.

 

Cheers,

Rob

[JMortensen]

Well it looks as though it is going to be very easy to drop the diff out. Why would you need to drop the frame out? Seems to me a lot of trouble to go to so that you can more easily remove the frame from the car.

 

Plus, your tube is roughly 1x1x.120" or 25x25x3 I believe that would be in mm. So that can't be all that heavy. The 1x1 is 1.44 lbs/ft. I'd guess you have maybe 5 or 6 feet in the rear, plus whatever you do in the front, and the material to tie them together. I can't imagine this thing weighing more than 25 lbs when its all done. Doesn't seem like a big deal. Am I missing something?

[Dan Juday]

Nice work Rob! I've been reading this thread with great anticipation of the final results. I love how this has been a multinational design collaboration of the international Z brotherhood.

 

I have also enjoyed trying to cypher what some of your more esoteric English expressions might mean. Lots of good clean fun.

 

I have a question for you regarding locating the new diff vertically in the new subframe. What motor and transmission are in your car? Those of us who have installed American V8's in our Z's find that the transmission output shaft is significantly lower in the car than the the original. So to get acceptable u-joint angles we need to raise the rear and or lower the nose of the diff.

 

You may want to do some calculations based on the angle and location of your trannies tailshaft before fixing in steel the height and angle of the diff. Even then I would suggest building in some adjustability.

 

My other thought on this is your screw in mounting bolt sleeves. Sorry to be critical, but I'm not keen on this idea. I understand the need to vent the tube for hot dipping. But my mind sees these things loosing up after some time on the road. The stress on them working the plating off where they meet the tube and causing the hole to open up and corrode. This may be an unrealistic worst case scenario, but if it were me I'd weld them on and drill a small vent hole in the top of the tube and fill it with a glob of goop just before I installed the subframe for good. At the very least weld three of them in and just screw in the last one.

 

To leave you on a positive note: props for your first time welding. Much better than my first scratches!

 

EDIT: Also wanted to give you a pat on the back for recognizing Mr. Tylers work in this area. An excellent, effective, and simple design that works wonderfully. Using his drawing I made one for my car that solved two problems at the same time.

[BlackBeaut]

Well it looks as though it is going to be very easy to drop the diff out. Why would you need to drop the frame out? Seems to me a lot of trouble to go to so that you can more easily remove the frame from the car.

 

Yep I appreciate that once it's in it should stay in and I can forget about it. The big advantage that I can see with this solution is that it's simpler to fabricate (well simple and me and fabricate are all relative terms of course ). The 3D render doesn't show things too well but the front end of things is around 2-3" lower (depending on how I make up the Ron Tyler mount) so we start having to deal with some awkward angles as things, erm, angle in to the end of the tranny tunnel. Using the rod ends means that they'll deal with the whole tricky angle side of things and I can just make the top frame on a flat surface then just bolt into place.

 

Nice work Rob! I've been reading this thread with great anticipation of the final results. I love how this has been a multinational design collaboration of the international Z brotherhood.

Thanks Dan, I've really enjoyed getting my head around this one and boucing ideas of other people. I also find it quite amusing that after going through all this Dave at ARZ comes along and bangs out exactly what I was after in the beginning without breaking a sweat

 

I have also enjoyed trying to cypher what some of your more esoteric English expressions might mean. Lots of good clean fun.

Well it's good to keep everyone on their toes. I actually work for a US company based in SF so I may speak a little more mid-atlantic English than most Brits, but it's always fun to throw in some weird little english saying to get the heads scratching

 

I have a question for you regarding locating the new diff vertically in the new subframe. What motor and transmission are in your car? Those of us who have installed American V8's in our Z's find that the transmission output shaft is significantly lower in the car than the the original. So to get acceptable u-joint angles we need to raise the rear and or lower the nose of the diff.

Engine is stock L24 at the moment with a KA tranny on it in the near future. Plan is to stick with the L but hopefully work my way up until I get to a 3.0l stroker running EFI ITBs and any other fun combination of letters that'll make it sound flash!

 

I'm planning on making the final connecting part that'll bolt to the two front ears on the diff and up to the top frame have a fair amount of adjustment in it, most likely I'll keep it simple and users spacer washers, so that I can get things like the pinion angle somewhere acceptable. Using my machined cross member I already have about 10mm extra room to play with under the prop compared to the stock member.

 

My other thought on this is your screw in mounting bolt sleeves. Sorry to be critical, but I'm not keen on this idea. I understand the need to vent the tube for hot dipping. But my mind sees these things loosing up after some time on the road. The stress on them working the plating off where they meet the tube and causing the hole to open up and corrode. This may be an unrealistic worst case scenario, but if it were me I'd weld them on and drill a small vent hole in the top of the tube and fill it with a glob of goop just before I installed the subframe for good. At the very least weld three of them in and just screw in the last one.

 

This is a good point and I must admit I've been thinking of welding them in anyway (at the top at least where they're easy to get to ) If I do go with a hot zinc job then I'll need to add a few vent holes in anyway so it wouldn't be as much of an issue.

 

To leave you on a positive note: props for your first time welding. Much better than my first scratches!

 

EDIT: Also wanted to give you a pat on the back for recognizing Mr. Tylers work in this area. An excellent' date=' effective, and simple design that works wonderfully. Using his drawing I made one for my car that solved two problems at the same time.[/quote']

Credit where credit is due I say, it's a good solution and like you say solves some tedious issues associated with the back end. Quite how much my take on it will ressemble the original I don't know, but the spirit will be there!

 

Cheers,

Rob

[TimZ]

Interesting - I was just thinking about the idea of using rod ends not long before you posted it. It solves very nicely the main problem that I had with the "Tyler" style mount - that being that it works just fine for one-offs, but I don't trust the repeatability of the positioning of the diff strap bolt holes for trying to make a saleable piece.

 

I was just thinking again (always dangerous), and thought of this - what about putting rod-ends in the mounting holes at the front of the diff, a clevis at the appropriate spot on your upper brace, and using two bars (clevis on the bottom, rod end on the top) to locate the front of the diff? You could even put multiple clevis points on the upper brace to accomodate different diffs.

 

...or now that I think of it, one centrally located pair of clevis might be able to accomodate all of the diffs. Hmmmm...

[CruxGNZ]

...that being that it works just fine for one-offs, but I don't trust the repeatability of the positioning of the diff strap bolt holes for trying to make a saleable piece.

Sorry to veer off the topic, but why do you say this? I made a few Ron Tyler mounts and wasn't able to test fit them on my own car before I sold them off. You're making me worried!

[BlackBeaut]

I took my strap off last night so that I could do some measuring around there. From the results I've got I'd say that the dimensions given for the Ron Tyler mount should cope OK. I found the bolts to be M10 at 65mm centre-to-center. The holes in the strap mount are 11mm diameter, with one elongated to 13mm wide, I guess Datsun weren't too sure themselves

 

Of course now I'm going to go back and measure the other side of the car to make sure!

 

Tim, I like your idea of hanging the front using a clevis/rod end system. The one draw back for me in using the S13 diff is it doesn't have the big fat ears with built-in bushings, so I wouldn't have any damping up front. I've got a rough idea at the moment of how I'll add in a bushed mount that I'll render up later. Life would've been much simpler if I'd have found a big eared diff in the first place though!

 

Cheers,

Rob

[TimZ]

Sorry to veer off the topic, but why do you say this? I made a few Ron Tyler mounts and wasn't able to test fit them on my own car before I sold them off. You're making me worried!

 

It's not really that far off topic, as it pertains to manufacturability of Rob's diff mount/subframe.

 

Manufacturers don't genrerally hold the position of every weld nut/mounting point on the unibody to very rigid specs. This would be very expensive, and it's simply not needed for everything. Things like the suspension pickup points and the headlight mounting system are usually controlled to tight tolerances - the suspension for obvious reasons, and the headlight mounts so that they don't run into certification problems and so the headlights can be aligned quickly at the plant. There are certainly other things that require tight tolerances, but those are the ones that I can remember offhand.

 

Now, let's look at the diff strap mount - if you look closely, the mounts themslves are a couple of tabs that were welded onto the unibody, possibly by hand (I don't know what the manufacturing processes looked like at Nissan in the 70's). The diff strap will still work just fine if that mount is anywhere within an inch of nominal. This was almost certainly not lost on Nissan's engineers when they designed the unibody, and I doubt seriously that they spent much effort on controlling the positioning of these mount points. It probably doesn't really move around by an inch from car to car, but 10cm (sorry for mixing units) wouldn't surprise me a bit - Rob's observation of the slotted holes in the tabs on the strap mounts indicate that they were not counting on the positioning of the weld nuts with respect to each other in the same tab to be repeatable to better than ~3mm. So, I doubt that they did any better of a job of locating those tabs in three dimensions in the unibody itself.

 

Now mind you, I don't have any proof of this for these particular mounting holes, and it's possible that the diff strap mount's close proximity to a suspension mounting point (which are generally well controlled) might help mitigate the problem. It would be a good thing to verify on several different cars - just something that I've suspected for a while, now.