Sirpent "Z"

[PeterAllen]

John - The forward control arm mount beam will most likely have to be round tube and shaped either over or under the input flange of the diff. You may also need to use a similar approach to the beams carrying the front mounting brackets as you need to keep them tucked up tight against the diff profile so that you maximise the space to also keep the exhaust tucked up in that area.

 

Great concept.

[Wayne G]

The rear end conversion looks great, as does the whole project.

 

A better way to maintain appropriate clutch cover to throw out bearing distance is to space the throw out bearing towards the clutch cover. Much safer with less dangerous forces involved. Just my two cents worth.

 

Keep up the great work.

[garvice]

Peter, Will the diff input flange not clear the standard front control arm beam?

I had to make a little allowance in mine when I lowered my diff so the passenger side bolt had more clearance, but the diff flange is definitely above the beam.

With the standard beam you then also have the exhaust cutout allowance.

[PeterAllen]

garvice - I think you may be right. I was incorrectly thinking about the strap mounting points which I have utilised. I had been thinking how I might tie those forward control arm points but I hadn't finalised anything, John's cradle nicely addresses that issue. These are old 'R&D' photos.

 

(edit) On third thouhts no, not the OEM brace. but a 25mm x 25mm one might.

[KatoKid]

the diff has a rear mounted insulator held in place by a single bolt to the diff cover and dual bolts from the insulator to the mounting point which in this case will be the new carrier design, while the front have an isolator mount either side, so the entire diff floats so to say within the cradle.

 

Beautiful John. You've done your homework, fully floating diff clears the way to design a cradle that, as you've said, does more than just carry the diff. Well done.

 

As suggested by others, close consultation with your engineer before you even cut any metal will ease the pain. Exhaust clearance will always be an issue so you need to have a good idea what you want to do there before you get to final cradle design.

[Sirpent]

Thanks Guys

 

The thumbnail sketch is just that and did a lot of measurements today of the original Z components so as to start a CAD file of the assy.

 

At this stage an exhaust notch has to be added, also as mentioned, and the rear carrier will have to include a centralised "Kick Out" on the upper beam to facilitate the rear diff mounting point.

 

I can now see that this entire unit will be in 2 sections the lower boxed frame supporting the control arms and the rear carrier.

 

Some design changes will mean that the lower control arm pivot depressions will be built into the carrier and the cross beam will also have these so as to dispense with singular clamps.

 

I did stuff up as I drew the front carrier upsaid down showing 2 separate clamps when in fact the body has the pivot depressions build into them meaning the front beam will be a single unit with a mirror image.

 

All in all however clearances look very good and it may allow me to incorporate diagonal supports also running from the upper carrier down to the lower front beam, this triangulation should make it a more robust assy, but will see as I get closer with the CAD drawings.

 

My only thoughts now are about the rear carrier mount points, the old moustache par pivots will work well but I'm also going to see if I can incorporate the remaining redundant hanger bolt points also, this will give me a 6 bolt point assy for the carrier, question is solid mount or incorporate a thin poly washer at each bolt point?

 

Any suggestions?

 

Cheers

 

John

[KatoKid]

I would go with some poly washers or something similar only because you will need something that can withstand the flexing of the body shell when driven aggressively, which I'm sure it will be! Anything too rigid will impart too much force to either your carrier or the body shell mount points that could cause cracking/fatigue.

 

My 2 cents worth.

[peter mc]

yer it must be soft mounted or the Floor will crack and the ride will suck, not good for such a cool car, i wont to be cumfy when we go cruzen

[Sirpent]

Fine Fine,

 

OK Boys then I will have to see what I can design just don't want that beam becoming too active as it will be dealing with suspension and differentail forces at the same time.

 

I will let one of you test drive it and the other ride shotgun on the test run while I watch for the arse end to fall out and the obligatory trail of sparks as it drags along the tarmac LOL

[peter mc]

hahaha im driven wont be the first time sparks come out the back end of a car i was driven

[garvice]

See I would have said the opposite. I would have thought solidly mount the bracket (like the standard one is) and use the poly mounts on the diff. Standard trailing arms already have a rubber/poly mount.

[peter mc]

yer that the way to do it ..

[Sirpent]

See I would have said the opposite. I would have thought solidly mount the bracket (like the standard one is) and use the poly mounts on the diff. Standard trailing arms already have a rubber/poly mount.

 

Valid point.

 

The carrier would act no differently from what a front engine cross member would and adding dampening to the hang points would be a waste of time as the diff and control arms would be insulated using poly dampeners/bushes.

 

Cheers

 

John

[KatoKid]

There's some good stuff on Hybridz re mounting short nose R230 and others, some including a similar cradle design. Cant put my finger on it just now.

[Sirpent]

Damn David,

 

Burst my balloon again, I thought this was an original idea !!!!!!!!!!!!!!!

 

What are your thoughts on the the latest assumption about not dampening the carrier?

[PeterAllen]

I recall that and I thought it might have been 'Blue Oval' - Terry Oxandale. It wasn't, but he has an interesting rear diff mount (see fuel cell album). Why he mounts the battery so close to the fuel tank I'll never know - well I do know, weight distribution but damn stupid if you ask me.

http://www.fototime.com/ftweb/bin/ft.dll/home?userid=7DC317B08EDB4B2EA837F708D07C9769&inv=9C67398D46D99D9

 

This might be what you were thinking of David.

http://forums.hybridz.org/index.php/topic/50499-differential-cv-lsd-hp-torque-r160-r180-r200-r230-diff-mount-faq/

[Sirpent]

Good call peter

 

He actually mentions adding dampening to one end (Rear in my scenario) while hard mounting the other (Front in my scenario)

 

http://www.fototime.com/ftweb/bin/ft.dll/detailfs?userid={7DC317B0-8EDB-4B2E-A837-F708D07C9769}&ndx=4&slideshow=0&AlbumId={309A8989-EFAC-4199-BC0D-20A43798D8B5}&GroupId=&screenheight=1024

 

Makes perfect sense, I should have thought about it in unisen as opposed to just the rear cradle, as he states, the solid mounted end actually absorbs the stresses and of course this translates to movement, that movement eventually leads to fatigue of the mounts and eventual failure, simple engineering.

 

Even though the front mounts will be dampened to an extent due to the control arm pivot bushes, the mount does nevertheless hard mount to the chassis, it is only the compressed bushes that dampen the arms torsional stresses, therefore even if the rear carrier was dampened at the bolt points, this would still add stress to the forward mount and most probably lead to bolt fatigue and failure.

 

Think this has been done to death now and I will just go solid rear mount.

 

That cradle is along the lines of what Im thinking for the lower section but is obviously a cut and shut of the orifginal components, good indicator however.

 

Thanks for all the input guys, well done.

 

Cheers

 

John

[Sirpent]

Update

 

After tossing and turning over the carrier, I decided to crank up the old CAD program I had and have a crack at seeing what could be done in terms of creating a CNC'd Aluminium billet carrier.

 

Attached is the preliminary wire frame image of what I have generated so far.

 

Still a lot of fine tuning to do.

 

Cheers

 

John

[Sirpent]

Rear carrier and front mount including twin 3" exhaust ports.

[Sirpent]

UPDATE

 

Final cradle design done showing single cut process of nested lower suspension mounts.

 

I have ordered a slab of 7075 - T651 Aluminium and the machinist is currently going over the CAD file I sent him.

 

Think this is more in keeping with the original concept and a much cleaner design.

 

Cheers

 

John

[benny]

looks great john.. are you considering selling the setup as a package for others that want this diff setup??

[Sirpent]

looks great john.. are you considering selling the setup as a package for others that want this diff setup??

 

Benny

 

If it all works I'm happy to supply the CAD file and details, however its not for the faint hearted, material and machining along with the 2 solid rod chromoly hangers which will bot into the two lower carriers will come in at $1000, overkill maybe, but as far as fitting a bullet proof short nosed LSD I think it will be a good investment.

 

I estimate that the rear end all together with this carrier, the diff, the CV billet axles, Arizona lower control arms, poly bushes and other associated adaptors etc will come in at around $3000

 

But lets see if it all works first, my vernier has been working overtime, fingers crossed.

[PZG302]

Looking good. Pity I'm not down south to take advantage of all the talent down there....

[Sirpent]

Looking good. Pity I'm not down south to take advantage of all the talent down there....

 

What were you after?

[PZG302]

The new toy will be an interesting build. If the dollars are available I would like to take full advantage of the freedoms under the rules, but I'm still a fair way from anything happening at this stage.