57 Chassis C4 Corvette Front and Rear, Stage 4 + SS Kit + 32 Gallon Fuel Tank by Hot

[fleetus macmullitz]

Looks good Russell.

Here's an idea if you decide to do the 4 door...

Give it the much better '57 Chevy coupe 'look' by copying the design of say the Mazda RX-8... how they keep the coupe look with the larger sized front doors with door handles; and the semi stealth smaller rear doors without door handles.

For me the door handles on only the front doors draw your eye to those doors.

[deuce_454]

I see a big flaw. the pinion support si hardmounted to the frame, and the rest of the centersection is rubbermounted...

and eliminating the longitudinal arm in favour of a rigid mount shows that whoever did the design hasnt done the math.



allow me to demonstrate:
500 ft/lbs of engine tourque, 3:1 first gear ratio, 3.55 rear end gearing = 500x3x3.55= 5325 ft pound of tourque to the halfshafts, and 5325 footpounds of opposite tourque acting on the diff... if teh distance from the halfshafts to the mounting pad is one foot.. then you will have over 5000 pounds of pressure on the pad... AND the same on the rubber in the transverse mount.. the rubber will deform.. and the steel in the mount on the diff will deform .. but the rubber will rebound...

if you guys had retained the longitudinal tourquer arm (that GM engineered for a reason i moght add)

the length of the arm (5-6 feet) would have reduced the pressure on the forward mount to about 1000 pounds... AND the rubber in the tranny to torquearm mount would not permanently deform and also reduce noise over your solid solution...

the rest of the frame looks great though.. but that mount needs fixing

[rat_rod_russell]

Originally Posted by compos mentis

Looks good Russell.

Here's an idea if you decide to do the 4 door...

Give it the much better '57 Chevy coupe 'look' by copying the design of say the Mazda RX-8... how they keep the coupe look with the larger sized front doors with door handles; and the semi stealth smaller rear doors without door handles.

For me the door handles on only the front doors draw your eye to those doors.

Interesting Idea, but the car I'm getting is already done. We're not the most awesome sheetmetal and I wouldn't want to bit that off as a short term project. Plus the 4 door I'm looking at is already done. I'll just drop it on my chassis then rock and roll.

Originally Posted by deuce_454

the rest of the frame looks great though.. but that mount needs fixing

looks like it works to me

https://www.youtube.com/user/RatRodRu.../1/qXEUpuXsHEk

Because the diff is mounted rigid to the front diff there is no twisting to the bolts just stretching. So the stress goes straight into the metal. You might notice that mount is .250" where the rest of the frame it .125" And for super HP applications we go the bottom of the diff and take it forward to the rear cross member just in front of it to spread the load out across the frame.

On my C5/C6 conversion 57 Chevy truck I learned that lesson a few times where I removed the transaxle but kept the corvette rear end. I build a diff adapter to put a traditional drive shaft yoke to the C5 C6 corvette rear. That diff we rubber mounted on 3 sides and it snapped the bolts in half at only 500 miles. Hit the link in my sig and you'll see what I'm talking about.

The torque arm on the C4 corvettes is as much of an "ease of assembly" or top down assembly design idea as it was for leverage. Do notice that the 5th gen camaros and 2009 Vipers went away front the torque arm in favor of short mounted differentials.

The chassis in the photos is #46 and never have we had some one break and differential except me. I was testing the small Dana 36 at the drag strip to see how much abuse they would take.

Thanks
-Russell

[ccracin]

Originally Posted by rat_rod_russell

Thanks I apprentice you taking time to voice a valid opinion. But let me know if this makes since. The lower link of the 4 bar when under acceleration is not pushed forward in a buckling load but rather pulled in stretching as the knuckle is twisted forward so the arm will not see both extreme loads at the same time. Also the lower arm is so short that there is not that much leverage on the arm. Tubes are .125" wall DOM 1020 (mild steel) and all tig welded. Finally for practical purpose we tested this mounting method on my black and white 57 Chevy that I road raced and auto crossed for 3k miles and streeted for another 9k and never had any issues with the rear sway bar either. (P.S. The black and white car has thinner wall, smaller diameter tubing too.)

Later
-Russell

Technically, that is not correct. With an independent set up like you have all torque loads essentially will be reacted by the center section. The knuckles in this case are just carriers and do not react any torque. If they do, you have a bad bearing. Therefore when under acceleration the wheels are pushing forward on the chassis. Consequently all 4 bars of the 4 bar are in compression with this design. This is unlike a solid rear axle with fixed bird cages and a 4 bar. As I said before, I can't say that you will definitely have a problem without much more info. If you have run this before and have success then you should be good. It never hurts to discuss these types of things. The chassis looks nice, I'm sure your customer will be pleased. Keep up the good work.

[rat_rod_russell]

Originally Posted by ccracin

Technically, that is not correct. With an independent set up like you have all torque loads essentially will be reacted by the center section. The knuckles in this case are just carriers and do not react any torque. If they do, you have a bad bearing. Therefore when under acceleration the wheels are pushing forward on the chassis. Consequently all 4 bars of the 4 bar are in compression with this design. This is unlike a solid rear axle with fixed bird cages and a 4 bar. As I said before, I can't say that you will definitely have a problem without much more info. If you have run this before and have success then you should be good. It never hurts to discuss these types of things. The chassis looks nice, I'm sure your customer will be pleased. Keep up the good work.

And I appreciate the conversation. So many people treat IRS suspension like a black box and never really discuss it. I was of the understanding that on the C3 / C4 corvette suspension and Jag type IRS suspensions that use a U Joint half shaft for the driving shaft AND one of the suspension links that a percentage of the torque reaction was pushed out to the knuckles?

And your right I got my link forces backward. I sat down to draw it out and realized my mistake. What can I say, I'm dyslexic and I still get my left and right backwards all the time. I'll leave my post unedited so I can receive my flogging.

I know right now I have a 71 corvette and a stock 88 corvette in my shop both getting work and I've driven both quite a bit in the last few days (buddies cars, they told me to ). The 71 with its single forward arm (and very short instant center) will squat if you look at it wrong. Stand on the brake and put it into gear and the back end will try to squat, any acceleration with traction will squat hard and the moment you break traction the back end tries to jump from the unloading spring. The 88 (and my past 57's) don't squat like that because of the dual forward arms. The instant centers moved up to the front of the car giving the load a longer lever against the car's suspension. Is that not torque reaction transmitting through the suspension to the tires?

Thanks again
-Russell

[ccracin]

Originally Posted by rat_rod_russell

And I appreciate the conversation. So many people treat IRS suspension like a black box and never really discuss it. I was of the understanding that on the C3 / C4 corvette suspension and Jag type IRS suspensions that use a U Joint half shaft for the driving shaft AND one of the suspension links that a percentage of the torque reaction was pushed out to the knuckles?

And your right I got my link forces backward. I sat down to draw it out and realized my mistake. What can I say, I'm dyslexic and I still get my left and right backwards all the time. I'll leave my post unedited so I can receive my flogging.

I know right now I have a 71 corvette and a stock 88 corvette in my shop both getting work and I've driven both quite a bit in the last few days (buddies cars, they told me to ). The 71 with its single forward arm (and very short instant center) will squat if you look at it wrong. Stand on the brake and put it into gear and the back end will try to squat, any acceleration with traction will squat hard and the moment you break traction the back end tries to jump from the unloading spring. The 88 (and my past 57's) don't squat like that because of the dual forward arms. The instant centers moved up to the front of the car giving the load a longer lever against the car's suspension. Is that not torque reaction transmitting through the suspension to the tires?

Thanks again
-Russell

First let me say I am not overly familiar with the differences between generations of Vette IRS designs. I am merely speaking from looking at general geometry.

What you are talking about with one design squatting and the other not has to do with the percent ani-squat built into each design. Anti-squat is independent of torque reaction. This is completely geometry dependent. The theoretical convergence point of the 2 links forms the Instant Center. The location of this instant center in relation to the CG is one of the factors that go into this calculation. With this in mind if you look under the newer car as you state both arms are point up to the front of the car. On the older design or single arm design this angle is not as steep. With the 2 arms pointed up to the front, when the tires start to roll forward and push the chassis the tires are forced down as they try to drive under the chassis. The reaction to this is actually trying to lift the chassis to some degree. This counter acts the reaction to the torque being applied to the center section. This reaction is trying to lift the front end of the car and because of the moment arm length, the rear goes down. The center section and it's mounting are the only components that are affected by torque. Without this angle, there is less to counter act the torque being reacted from the center section so the rear squats.

These are just my thoughts on what you are seeing. Suffice it to say, I still believe your links will be in compression during acceleration. So, as you are accelerating out of a corner with body roll involved you will be loading those links in compression and bending. Is it going to be a problem? Don't know. Could it be? Yes. Were it me I wouldn't take the chance and just tweek the bar design a bit. I attached a quick sketch of how maybe to change the swaybar mount to stiffen the bar and not worry. Anyway, please don't take any of this as more than some interesting conversation. I love talking about this stuff. Keep up the great work!

[rat_rod_russell]

Exhaust upgrades!!!

So Don sent his chassis back over so I could drop an LS1 and T56 in and fab up an exhaust. So here I drew it up in the computer so I could figure out how many bends I needed and at what angels then I was going to FAB it up after buying a bunch of mandrel bends. Then I thought, I've got it all drawn up. Lets see if they can bend it as one part. And the answer was yes and it turns out its going to be a lot less expensive than we expected. So with any luck in a week or so we should have 6 parts coming in. I'll still need to FAB the x pipe together from 4 of the parts but that beets the 18+ bends I was going to have to cut and butt weld.










-Russell
Hot Rod Jim's

[rat_rod_russell]

Originally Posted by ccracin

First let me say I am not overly familiar with the differences between generations of Vette IRS designs. I am merely speaking from looking at general geometry.

What you are talking about with one design squatting and the other not has to do with the percent ani-squat built into each design. Anti-squat is independent of torque reaction. This is completely geometry dependent. The theoretical convergence point of the 2 links forms the Instant Center. The location of this instant center in relation to the CG is one of the factors that go into this calculation. With this in mind if you look under the newer car as you state both arms are point up to the front of the car. On the older design or single arm design this angle is not as steep. With the 2 arms pointed up to the front, when the tires start to roll forward and push the chassis the tires are forced down as they try to drive under the chassis. The reaction to this is actually trying to lift the chassis to some degree. This counter acts the reaction to the torque being applied to the center section. This reaction is trying to lift the front end of the car and because of the moment arm length, the rear goes down. The center section and it's mounting are the only components that are affected by torque. Without this angle, there is less to counter act the torque being reacted from the center section so the rear squats.

These are just my thoughts on what you are seeing. Suffice it to say, I still believe your links will be in compression during acceleration. So, as you are accelerating out of a corner with body roll involved you will be loading those links in compression and bending. Is it going to be a problem? Don't know. Could it be? Yes. Were it me I wouldn't take the chance and just tweek the bar design a bit. I attached a quick sketch of how maybe to change the swaybar mount to stiffen the bar and not worry. Anyway, please don't take any of this as more than some interesting conversation. I love talking about this stuff. Keep up the great work!

Holly crap I can't believe I forgot about this. Just got cough up in work and it went to the back of my head.

But the way I understood it was that the torque reaction trough the diff on a live axle was why the the instant center of the froward arms was pushed so far back in the car, closer to the center than the front of the wheels. So I thought the torque reaction would transfer through the cv or half shaft and would influence the anti squats location because of that transfer. Is that off track?

-Russell

[legend]

over time it'd rip the threads out of the top of the diff

[rat_rod_russell]

Originally Posted by legend

over time it'd rip the threads out of the top of the diff

there are no threads on the top of the differential, so ripping them out would be difficult. FYI the rear wing bushings are 90 series urethane so they won't deflect like normal rubber or even the 60 series urethane most bushing are made from.

-Russell