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 Post subject: Critique my frame
PostPosted: October 15, 2020, 9:03 am 
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Joined: January 1, 2015, 1:55 pm
Posts: 294
Hello All, I've had a little publicity for my Cheetah Roadster Tribute. As a result I've had inquires about getting a kit for it. The kit would be basic. 2 piece body in white, unpainted frame, aluminum panels to skin the frame, instructions and a parts list to duplicate my build. I'm thinking the price will be $7999.00.

I've sold a few bodies and and a couple of frames. Before I go further I would like opinions/constructive input concerning my frame. I've made arrangements to have future frames welded by a professional. A fiberglass company has my molds and makes bodies for me. I'm not looking to make a living from this. When things get back to normal I would like to go to some car shows with my Cheetah. I like getting out and seeing people and talking cars. :) If I sell any that's a bonus.

I welded this frame. I'm not selling it. The frame is constructed of 1.5 X 1.5 X .083 and 1 X1 X .065 tubing.

Still here and having fun! I've put 4,000 miles on the car this summer.

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 Post subject: Re: Critique my frame
PostPosted: October 15, 2020, 10:04 am 
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Joined: January 1, 2012, 12:44 pm
Posts: 477
Location: Boise, Idaho
Given the potential for a heavy lump in the engine bay, I'd suggest triangulation or gusset of the shock mount to the vertical tube.


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 Post subject: Re: Critique my frame
PostPosted: October 15, 2020, 9:25 pm 
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Joined: January 28, 2016, 7:59 pm
Posts: 157
Location: Omaha, Nebraska
The frame looks good, and I'm sure it would work well as it is, but here are a few things that might make it better:

1) Overall it's probably too much steel, therefore heavier and more expensive than it needs to be. A lot of the 1.5" tubing could have .065 wall, and many of the 1" square triangulating tubes could be round 3/4" instead. I would not be surprised if you were able to reduce weight and material costs by 20-30% while maintaining the same safety and stiffness.

2) I would not leave open ends on tubes, but rather plate them, or, better yet, use elongated plates that cap the ends and tie into the conjoining tubes. It would be simple to do, much stronger, and keep the insides of the tubes more protected from corrosion.

3) I'd add a couple of gussets where the rear portion (cantilevered over the rear wheels) contacts the central portion. A lot of stress is delivered right there, and it would be good to spread that out over more steel and more weld.

Hope that helps.

-Graveyard

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 Post subject: Re: Critique my frame
PostPosted: October 16, 2020, 7:42 am 
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Joined: January 1, 2015, 1:55 pm
Posts: 294
Thank you for both of your suggestions. I agree about adding gussets to the front upper shock mounts.

It looks like I could save about 11.5% weight if I used 1.5 X 1.5 X.065 and 1 inch round by .065. ( I just reread and saw that the suggestion was for 3/4 tubing. The frame with out brackets weighs about 230lbs. I would save about 26.4lbs by making those changes.

The red car pictured is running an all iron SBC. The body is 3/16 thick. The total weight with all fluids and 6 gals of gas in 1912lbs.

I have a fresh LS1 and a light weight body. (3oz layup). With those changes the weight would be around 1760Lbs. If built the frame with .065 tubing and round tubing for the triangulation it looks like I could save another 26-30lbs.

I have enough steel to build a couple of frames. I think I'll use what I have for that then look at improvements and weight savings going forward.

I'm heading to the shop to start the next frame. Have a great day!


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 Post subject: Re: Critique my frame
PostPosted: October 16, 2020, 5:31 pm 
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Joined: April 15, 2014, 1:54 pm
Posts: 468
I recall that the original Cheetah chassis was found to be too flexible, so I don't think you have too much weight in it. I would love to do a torsional analyses if you will share chassis dimensions. I recognize that this info is proprietary, so your call.


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 Post subject: Re: Critique my frame
PostPosted: October 19, 2020, 8:44 am 
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Joined: January 1, 2015, 1:55 pm
Posts: 294
Bobber wrote:
I recall that the original Cheetah chassis was found to be too flexible, so I don't think you have too much weight in it. I would love to do a torsional analyses if you will share chassis dimensions. I recognize that this info is proprietary, so your call.

Thank you for your offer Bobber. I would greatly appreciate an analysis. I'll get some measurements and post them. I can't draw at all. I wish that I was able to create a good schematic. Heading to the shop.


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 Post subject: Re: Critique my frame
PostPosted: October 20, 2020, 8:10 pm 
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Joined: April 15, 2014, 1:54 pm
Posts: 468
I'd be happy to help out. I will need to draw it up myself for the model geometry so I can give you any drawings you need for fabrication.


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