Rear cornerweight for light SC?

beepbeep · 02-24-2005, 11:24 AM

Hello there!

We are going to glue threaded pipe on rear dampers, in order to convert it to coilover suspension.

We have 475lbs/in springs and would like to measure their depressed lenght, so we can find the ballpark of where to glue the threaded pipe so we don't install it out of adjusting range.

So: what's the typical weight on 911 SC rear wheel with engine installed?

Thanx!

SC-targa · 02-24-2005, 01:37 PM

Figure that your cars weighs maybe 2,700 pounds, with 60% on the rear wheels (1620 pounds). Divide by two and that's 810 pounds per wheel.

Jerry Kroeger

Wil Ferch · 02-24-2005, 02:00 PM

That'll be one heck-of-a glue !!!!

Glue ??

Wil

beepbeep · 02-24-2005, 03:02 PM

Thanx Noah!

According to my calculations, our 80N/mm springs will compress around 50mm under weight of the car.

Quote:

Originally posted by Wil Ferch
That'll be one heck-of-a glue !!!!

Glue ??

Wil

Yepp. Glue.

These things are glued on each other:

Don't worry, I already calculated worst-case shear loads for this and we still have safety factor of 6-7 on this particular glue. It sounds weak but in reality, area that is going to be glued is big and this glue has helluva good properties

trak ratt · 02-24-2005, 03:32 PM

Sounds like an interesting project. Are you going to reinforce the to upper shock mount, what type clue? Did you revalve the Bilsteins

beepbeep · 02-24-2005, 03:44 PM

Yupp, upper shock mount is going to be reinforced a little. It's two-component epoxy glue.

Glue joint is the least problem. This glue has ~17MPa shear strength... five ton force on our glued joint would subject it to 0.83MPa...that's a safety factor of around 20, using 50000N force (3500N is force on joint with car standing still).

Glue is probably the very last thing to fail.

ttweed · ttweed's Garage

Quote:

Originally posted by beepbeep
Glue is probably the very last thing to fail.

As long as your surface prep is immaculate and you are using a high temp epoxy, there's no reason that won't work, I suppose, but why not just weld it, or buy a threaded body shock?

TT

KobaltBlau · 02-24-2005, 04:45 PM

Quote:

Originally posted by beepbeep
So: what's the typical weight on 911 SC rear wheel with engine installed?

your engine or our engine?

beepbeep · 02-25-2005, 01:01 AM

Quote:

Originally posted by ttweed
As long as your surface prep is immaculate and you are using a high temp epoxy, there's no reason that won't work, I suppose, but why not just weld it, or buy a threaded body shock?

TT

Welding is not possible as shock-absorber walls are too thin and there are rubber grommets inside that would be destroyed by heat. Buying threaded shocks would be best but they are too expensive and this is "budget" project

Kobalt: yeah...engine will weight roughly 90kg less, but I would like to know the ballpark with 911 engine to begin with

Wil Ferch · 02-25-2005, 05:41 AM

The spec strength of glue is one thing...but I would like to know long term effects of impact/shock loads ( pardon the pun1)...and local heat, especially if you retain stock heating system where a ton of waste heat gets dumped in this area by the heater flapper valves..

I dunno...maybe add another "sleeve" above the normally threaded tube that you glue on, and have that sleeve be retained at the top and bottom in some way.

Is this glue a new application? ( have others done it before?). What are others' long term experience?

Wil

beepbeep · 10:03 AM

We know of one endurance racer that used this method on his Alfa Romeo GTV and it worked.

There will be no "stock heating" system dumping heat in this area...heting will be done by water/ait heat exchanger in the cabin

(It will be the first SC with working heat, i hope)

Speaking about "shock" loads: as you probably understand it's only spring loads that are transfered trough glued region. Shock "shock" loads are transfered trough shock absorbers pickup-points.

Springs will do it's job by dampening the transient loads. Even if they compress totally, it will take approximately 15 times the normal weight load (50000N) to load glued joint to 0.8MPa. Structural limit for this particular glue is around 15-20MPa :-)

I suspect that suspension pickup points are going to give long before glue fails...

echrisconnor · echrisconnor's Garage

Lightweight C3 weights here with me in the driver's seat:

Front: 496 416
Rear: 744 656