Lightening solid motor mounts on FC's
 

Hey guys I was just pondering how much solid aluminum motor mounts are going to weigh and being performance minded as I am I was thinking about having a shop drill out some of the material around the circumference of the mounts themselves.

sort of like the pic I have here....

https://www.rx7club.com/attachment.p...id=76389&stc=1

What do you all think? Too much material removed? Too little?

Here is another idea: Having a machine shop cut out the material in a concave/convex? shape around the mount creating an hour glass typ of shape.

https://www.rx7club.com/attachment.p...id=76391&stc=1

The solid Aluminum mounts are actually pretty light (for a solid metal mount).. lightening them further may not help you out all that much in the grand scheeme of things. But, a few holes equidistantly placed will not affect the structural integrity to the point to cause failure.

HOWEVER.. you want to be careful about cutting away TOO MUCH material, the amount of holes you show on the diagram is WAY overkill.

If you MUST drill out the mounts, i wouldn't go more than 4 or 5 1/2 inch - 3/4 diameter holes per mount. You want to keep the amount of metal between each hole as high and as equal as possible to keep the structural rigidity of the mount.

The weight saved from doing that would seem negligable (sp?) in comparison to the importance of the strength of motor mounts. But I'm pretty much guessing here.

Obviously that pic was just a quick photochop. I haven't ordered mine yet as i am still a broke ass. But I will check out what I can do when/if I do get them. has anyone copared the aluminum units sold by scaliwag and that other guy on the forum and stock/comp. mounts?


Santiago

Isn't this about the same weight difference of going jogging before driving, or whereing a teeshirt instead of a sweatshirt? Maybe if you had a completely, and I mean COMPLETELY gutted car, and you weighed 130lbs, and you STILL wanted to be have the car lighter... then maybe...

Why not remove the quarters that rolled under the driverseat, theres probably more weight there...?

I weigh 123 pounds.

I normaly wear minimal clothes like a white undershirt. My car isn't gutted out but the point of making small contributions to the weight redux account is that little by little you can make a difference in the car's weight.

there's the arguement that a pound out of 100 places will save you a hundred pounds, which is where this arguement would have to go. the motor mounts are very light. i was tossing them around and playing with them (they roll!). the trouble of cutting extra holes could be spent on more productive things... like firing your shipper !

geez, I thought I was the rx-7club lightweight champ too, you got me beat by 12lbs.

i'm glad i'm not a skinny. i weigh in at a comftorable 185. too bad all it is in my legs and no longer in my upper body since i stopped lifting weights
Anyway back on subject, want to give me a link to wgere i can look at and perhaps think about purchasing these motor mounts?
Thanks,
Matt:)

take a shit before you race that will save you more weight

IMO Kenteth is on the right track, you're over worrying a trivial situation. Small weight differences matter, but add it up all the extremely minor weight savings and then add them back. Can you honestly tell the difference between 2650lbs and 2620lbs? I'd be impressed if the two guys on this forum who actually race their cars competitively can tell the difference. (and by that I don't mean the psychomatic difference- "I changed the oil and it feels like I gained 50hp!") There are certain things that it doesn't make sense to do. Also, would the shop charge you anything to do it?

Can you tell the difference between you driving and you driving with a passenger? I can. That is more than 30 pounds but with some work you can make a noticable difference.

5'10; 120.5 pounds. bathroom scale, not sure how accurate it is. am i the lightweight (male) champ?
but yes, a poopoo before racing would save about the same weight as lightening the mounts.

as for the mounts, check ebay or PM scalliwag. i dont know his exact ebay name, but i believe its "scalliwag_performance" or similar. theyre about $50 for the pair.

Damn you skinny bitch. You looked like 160 easy. >:O

And you guys must have some heavy shit comming out of your ass.

I think there will be little advantage to lightening the motor mounts. Probably no more than 1.5-2lbs in weight savings? Not worth it in my opinion.

"worth it"

to me doesn't matter unless the cost is above ~$20 somehting that isn't worth it to me is a CF hood for "lightening" spending 500 to 700 dollars buying/shipping/painting a hood for 10 pounds over an aluminum hood is bull shit.

Well, you've convinced yourself that its worth the <2lbs it so I won't argue about it anymore.

Anyways, as others said, as long as you don't drill out too many holes to ruin the structural integrity, you should be fine. The hour glass setup would be pretty expensive for a machinist.

Ya'll suck.... I've been pondering gutting my car for weight savings and all that.... then i thought to myself...... Hey asshole, you're 6'3 and weigh 240 lbs.. when you had a washboard stomach, you still weighed 210... so thats like 30 lbs i could lose without looking like an AIDS patient.... so whatever i do to my car, I'm still putting over 200 lbs of dead weight into it everytime i drive the damn thing......

the flip side is... EVERY LB you take out of the car lowers your HP/Weight ratio number. and THAT is the key to our cars becasue of the crappy torque numbers a rotary produces.

The effect is cumulative as well..... taking half a pound out in one place doesn't do a whole hell of a lot, but if you take a TOTAL of 200 LBS out of your car by little mods here and there, you are going to have a noticeable difference.

John Force once said: "these guys spend thousands of dollars trying to shave an ounce off the car here and there..... It don't cost nuthin to take 50 LBS off the driver! In Fact, not feeding ME for a week will put a tank of Nitro in the car!!!"

Well I am aware that the gain would be MINIMAL at best but pound per dollar I think that this is still better than say buying a composite hood/fenders/hatch etc.

Think about it:

~20 to drill ten holes in the mounts for a gain of maybe 1-2 pouns that is between 10-20 dollars per pound of redux.

Now 700 dollars or so to have a good quality hood made shipped and painted for you for 10-20 pounds of savings. That is around 35-70 dollars per pound.

do NOT do the hour glass setup, that will be a disaster..... (ideally) the force of the motor is going to be transmitted THROUGH the mount from top to bottom in a straight line... if you try to draw a straight line through the hour-glassed shaped mount, what happens??? No metal in the middle, no line!! What you will end up with there is broken motor mounts the first time the engine twists.

Go take a look at a 3" body lift puck for a pickup or jeep. They usually have a honeycomb shape, similar to what you were describing in your first picture. Light and strong!!

How much do the mounts weigh before cutting them up?

My guess would be around 3-5 pounds each?

I just got word from one of the manufacturers of the mounts. His weigh in at 24-25 ounces each!

That sums up to 1.5625 pounds! Damn!