Engine Carrier

[randywebb]

These big heavy chunks of steel which are hung way out at the back of car are continuing to annoy me. It doesn't keep me up at night, but it just keeps bothering me. For pitch and yaw, it is the worst place to have a big piece of wrought iron.

[randywebb]

I know Thom drilled holes in his -- how much weight did that save?

And what did you do, Thom, to keep dirt and crud (and hot air) out of there?

An alternative wold be to make one out of some other material... I assume that anybody that designs aluminum lug nuts would use Al here too, if they could get away with it. So my guess (see Island's recent thread on Beating the factory engineers & the "rebuttable presumption post in that thread),
is that Al will not work in this application. Again, I'd guess that the many repeated stresses on an Al piece would cause it crack {not sure what you'd call that material property - "toughness"?}. We can surely rule out Magnesium too.

Carbon fiber also doesn't seem like it would work. Gets hot in there for one thing.

That leaves Ti, titanium. It flexes well -- more than most steels IIRC. I wonder if a couple of sheets could be bent into the right shapes by hammering or pressing over a wooden buck, and then welded together to make a carrier piece?

Apparently, it isn't that hard to weld Ti...

More importantly, who can I get to do this and sell some of them....

[randywebb]

This thing...




Porsche calls it a 'bracket' - p/n 901-115-014-14

It is a #1 offender for adding weight at the extreme rear of the car.

[Bobboloo]

Why not just get rid of the part and build a brace similar to the 996 motor. One part weighs less than two bolted together.


The engine tin would need to be redesigned as well but it's do-able.

[Bobboloo]

Properly designed it could even be cut from billet aluminum.

[Porsche_monkey]

Originally posted by Bobboloo
Properly designed it could even be cut from billet aluminum.

That was my thought. Draw it up in CATIA or SolidWorks and send it to a machine shop. CNC work is cheap now.

[rusnak]

I thought Ti was very hard to weld and/or machine.

I'd look at carbon fiber or fiberglass/aluminum. The stuff that race teams would use.

The 914-6 uses an interesting center mount that would be lighter than the 911 set up.

On the other hand, that weight is not a bad tradeoff because it is low in the car. The worst place to have weight would be to the rear and high, I would think.

[randywebb]

that far back, you can't get much higher....

Are you guys saying it's cheaper to CNC it out of an Al block than to stamp it??

[gerard vaglio]

This thread should be sent directly to WEVO.

[HarryD]

I would think you need to be careful to understand the stresses these parts see to ensure that the lighter weight part is not deforming under load and causing other problems. Because of this, I think it will be more than just making the same part out of aluminium. Some thought/testing will need to be done to properly strengthen this piece.

In the '60s/'70s did Porsche place a light weight piece here in their race cars? They were in a major quest for lightness, I think they would have considered this spot as well.

[Bobboloo]

To prototype a piece from sheet metal would cost about $3000. Making copies would be substantially cheaper of course. If your looking at mass production then this will be cheaper in the long run.

For making just one-offs, however, it would be cheaper from billet aluminum I would think. You can test and make changes as needed as well.

When you consider that the 993 rear suspension is cast aluminum there's no reason to think this part can't also be made of aluminum specially considering the motor mounts have rubber bushings.

Aluminum might not be ideal if solid motor mounts are used though.

P.S. What does 1) necessary and 2) noticable have to do with this hobby? Let the pragmatists drive Honda Civics.

[euro911sc]

Welding Ti is a pain and requires some special gas/filler materials as well as a vacuum chamber, ideally...

cut it from billet AL... or just drill holes like the rest of us cheap bastards

Best regards,

Michael

[911pcars]

One can drill lightening holes in the cross mount bar, but weight will be added with welded stiffening along the edges (because you removed the mass from the middle where the new holes are).

The net effect with the factory bar is a holey look at about the same weight. An alternate material with a higher strength-to-weight ratio is better. Ti would be nice... and expensive.



Sherwood

[randywebb]

Originally posted by Noah
For me, they have everything to do with this hobby. That's why I spend my time and money on things that will actually make my car perform better.

- Taking a significant amount of wt. off of the extreme rear of the car CERTAINLY should make it perform better.

Do the math.

Pick an estimate of the Center of Gravity and multiply the wt. savings times the distance. That will give you a figure of merit to compare with "RS door panels" or a FG or Al deck lid.

[Bobboloo]

Sherwood,

What engine is that aluminum cradle for?

[911pcars]

Bobby,
I believe it's for a 3.6 transplant.

Sherwood

[rusnak]

The 914-6 setup has a central bolt at the engine crankshaft pulley end, and ears that are wide set at the tranny end. This would shift the weight forward, but not add any other benefit.

That cnc Al piece shure are purty tho.

[450knotOffice]

Randy, I have to agree with Noah on this one. That assembly weighs maybe 15 pounds. Yes, it is at the extreme rear of the car, but it is also attached directly to the engine and can therefore be considered just another part of the engine. Now, considering that these engines weigh hundreds of pounds, the act of removing maybe 5 to 8 pounds from that huge mass will have no noticeable effect simply because those few pounds are but a tiny fraction of the total weight of the engine. Yes, it is located far from the center of gravity and yes, I am familiar with Weight X Arm = Moment, but let's be honest for a moment, I doubt any driver on this board (even the pro racers) would notice any difference at all between the stock assembly and a lightened one, in terms of the car's handling dynamics or its lap times.

I agree with Noah. There are better ways to spend one's money on these cars, unless one likes to simply throw money and time away.

[Jeff Alton]

I am going to weigh my spare one..... then I will comment....

Cheers

[Bobboloo]

The total weight is an accumulative effect. This area is but one but when added with other lighter parts can make a substantial difference.

For example, replacing just the steel decklid with an aluminum one would probably yield very little difference. Does that mean it's a waste of time? No specially when the person doing it enjoys the process which was my point about a hobby. If someone wants to build a sand castle lets not kick it over because we might think it's a waste of time.

If someone is seriously trying to improve the performance of the car for better track times then this is actually an area to investigate. You could incorporate this weight loss with a weight distribution at the same time. In otherwords, you could design the bracket to not only be lighter but it could also serve to move the motor forward and lower in the chassis. The tranny mount would need to be modified as well but this is do-able and has been done. Moving the tranny and motor forward toward the center of the car even as little as a half inch should make a difference in the balance of the car.

You could design a combo package, tranny and an engine cradle/cross brace, that would lighten the car a little and move the drivetrain forward and lower in the chassis.

I'll venture to say that these combined mods would "add" up to a difference you would not only feel but could measure results on.