Need help from mechanical engineer on Custom Caltrac bars

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BrazilianZ28Camaro
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Re: Need help from mechanical engineer on Custom Caltrac bar

Post by BrazilianZ28Camaro » Wed Feb 05, 2014 7:06 pm

John Wallace wrote:Try this web site:

Billy Shope's Calculators


Here's a web page made by HO Racing back in the day, on working with leaf spring suspension.

Leaf Spring Calculation

:)
Good reading for sure!

Thanks for the links John!
'71 Z28 Pro-Street Camaro
Pump gas -T-ram - All motor SBC 427"
3308 lbs- leaf spring/Caltrac Car
29x10.5 Hoosiers
New best 1/8 mile ET
1.45 60' / 4.12 330' / 6.38@109mph :D

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Re: Need help from mechanical engineer on Custom Caltrac bar

Post by Brian P » Wed Feb 05, 2014 8:07 pm

Just be aware that the type of "traction bar" illustrated on that page is not transmitting forces in the same way as yours.

With the one on that page (the old, traditional style), when the axle starts wrapping up, the rubber bumper contacts the spring and stops further movement. The link is not in tension or compression but rather is in bending. Your lower link rod cannot transmit bending but does transmit tensile or compressive loads, as the case may be.

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Re: Need help from mechanical engineer on Custom Caltrac bar

Post by nhrastocker » Wed Feb 26, 2014 11:36 pm

Remove the sway bar!
CalTracs are not meant to use a sway bay.

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Re: Need help from mechanical engineer on Custom Caltrac bar

Post by BrazilianZ28Camaro » Thu Feb 27, 2014 4:44 pm

nhrastocker wrote:Remove the sway bar!
CalTracs are not meant to use a sway bay.
I aways wondered about that and I'll do!

The front SB is off already. :mrgreen:

Thanks for the tip !
'71 Z28 Pro-Street Camaro
Pump gas -T-ram - All motor SBC 427"
3308 lbs- leaf spring/Caltrac Car
29x10.5 Hoosiers
New best 1/8 mile ET
1.45 60' / 4.12 330' / 6.38@109mph :D

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Re: Need help from mechanical engineer on Custom Caltrac bar

Post by nhrastocker » Thu Feb 27, 2014 6:35 pm

BrazilianZ28Camaro wrote:
nhrastocker wrote:Remove the sway bar!
CalTracs are not meant to use a sway bay.
I aways wondered about that and I'll do!

The front SB is off already. :mrgreen:

Thanks for the tip !
Yep...it is binding the movement of the leaf springs and bars.

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Re: Need help from mechanical engineer on Custom Caltrac bar

Post by Dan Timberlake » Sat Mar 01, 2014 12:19 pm

BrazilianZ28Camaro wrote:
2seater wrote:Lovely work. Not really related, but isn't that directional tire running backwards?
......................
Too bad the car ran the same sixty foot time as before! At least I learned something.(Trunk ballast is king with street radials) :lol:

Thanks for reply
============================

Do you ballast just for more rear weight, or more right rear wheel weight?
http://www.web-cars.com/corvette/1963_S ... php?page=4

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BrazilianZ28Camaro
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Re: Need help from mechanical engineer on Custom Caltrac bar

Post by BrazilianZ28Camaro » Sat Mar 01, 2014 7:15 pm

Dan Timberlake wrote:
Do you ballast just for more rear weight, or more right rear wheel weight?
http://www.web-cars.com/corvette/1963_S ... php?page=4

Both. At the time I raced with street radials, the trunk ballast was about 160 lbs, being 100 on the passenger side and 60lbs in the driver side. Weight transfer was the prime goal, it worked like as spected, but we ran at 1/8mile straight of race circuit slight uphill and the grip was terrible.

When I relocated the battery to the trunk the car were five hundredths faster.
'71 Z28 Pro-Street Camaro
Pump gas -T-ram - All motor SBC 427"
3308 lbs- leaf spring/Caltrac Car
29x10.5 Hoosiers
New best 1/8 mile ET
1.45 60' / 4.12 330' / 6.38@109mph :D

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Re: Need help from mechanical engineer on Custom Caltrac bar

Post by shoedoos » Wed Mar 12, 2014 10:01 pm


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Re: Need help from mechanical engineer on Custom Caltrac bar

Post by pdq67 » Sat Mar 22, 2014 3:38 pm

I hate to be a drag, but I am a firm believer in the good old fashioned "slapper bars"!

I made mine such that they slapped right in the middle of the bottom of the front spring eyes! I used 1/2" bolts and nuts so that I could close or open the gaps to tune them.

I also mounted coil-over, shock overload springs that I used to tune as well as set my rear ride height!

And I did have a 3/4" diameter rear sway bar.

My rear end was noisy to say the least, but once I had tuned it, my car left like a rabbit out of the chute at the dog track!

pdq67

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Re: Need help from mechanical engineer on Custom Caltrac bar

Post by Rizzle » Sun Mar 30, 2014 1:24 am

I wouldn't be too worried about the strength of your custom bars since they are beefy two force members. Where you'll probably see failure first if the forces get high enough, is the front fastening arrangement. That bolt has a lot of distance to cover between the two mounting points, and is likely to bend long before your caltrac bars do. (This is based off the last pic of the last set of pics).

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Re: Need help from mechanical engineer on Custom Caltrac bar

Post by BrazilianZ28Camaro » Sun Mar 30, 2014 8:05 pm

Rizzle wrote:I wouldn't be too worried about the strength of your custom bars since they are beefy two force members. Where you'll probably see failure first if the forces get high enough, is the front fastening arrangement. That bolt has a lot of distance to cover between the two mounting points, and is likely to bend long before your caltrac bars do. (This is based off the last pic of the last set of pics).

Yep. At the time I assembled the bars I didn't like the distance triangle-to-triangle the M12 10.9 bolt had to cover. Even with the two billet SAE 1020 bushings with about 18mm O.D. and torqued to 50lbs, they aren't "pretty to the eye".

As this bolt tensile strenght is very high, I probably will fabricate new hardened bushings so I can torque them to 80-90 lbs without distortion. :mrgreen:

Thanks for reply.
'71 Z28 Pro-Street Camaro
Pump gas -T-ram - All motor SBC 427"
3308 lbs- leaf spring/Caltrac Car
29x10.5 Hoosiers
New best 1/8 mile ET
1.45 60' / 4.12 330' / 6.38@109mph :D

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BrazilianZ28Camaro
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Re: Need help from mechanical engineer on Custom Caltrac bar

Post by BrazilianZ28Camaro » Sun Mar 30, 2014 8:11 pm

pdq67 wrote:I hate to be a drag, but I am a firm believer in the good old fashioned "slapper bars"!

I made mine such that they slapped right in the middle of the bottom of the front spring eyes! I used 1/2" bolts and nuts so that I could close or open the gaps to tune them.

I also mounted coil-over, shock overload springs that I used to tune as well as set my rear ride height!

And I did have a 3/4" diameter rear sway bar.

My rear end was noisy to say the least, but once I had tuned it, my car left like a rabbit out of the chute at the dog track!

pdq67

I can't disagree with you, specially after seeing some pics of the Grumpy's Toys. :mrgreen:
'71 Z28 Pro-Street Camaro
Pump gas -T-ram - All motor SBC 427"
3308 lbs- leaf spring/Caltrac Car
29x10.5 Hoosiers
New best 1/8 mile ET
1.45 60' / 4.12 330' / 6.38@109mph :D

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