need some advice on billet strength for serpentine setup

[hessdawg]

hey everybody
im building a serpentine set up for my olds 455. it will hold 2 sanden air compressors, ambulance alternator and an s10 steering pump. i have mocked the brackets out of 3/4 mdf, and was planning to do them out of 3/4 billet. after 6 months of waiting for a buddy to hook me up with a price from a machine shop to replicate the brackets in 3/4 billet i got impatient, bought some 1/4 billet and cut them out myself on the band saw. now I'm second guessing myself and i'm wondering if the 1/4 is going to flex. the pieces are roughly 15x19 inches, and here are some pics of them. ok so my questions to everybody are
do you think 1/4 6061 billet will flex to much in the application?
how much do you think it would cost to cut this out of 3/4 billet (water jet, laser, cnc)
anybody know of a shop near monterey california that could do something like this for me
thanks brad
https://static1.pt-content.com/images/pt/2011/10/photo8-1.jpg

https://static1.pt-content.com/images/pt/2011/10/photo9-1.jpg

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[langtown]

Hessdawg

I would go with at least 1/2" . The main bracket for the billet specialties tru trac kit is 1/2 inch billet . I made some brackets recently for belt driven fuel pumps out of 1/2 inch and it was more than adequate.

Mcmaster carr says it is 436.00 just for the (3/4) material (1/2" was 340.00) It should only take a shop a few hours to set up the machine and cut the pieces. so it would probably be around 800.00 to get it done.

[hessdawg]

man i with i had seen this earlier. unfortunately i already bought the 1/4 inch plate for $90. used a band saw to rough cut then a router to finish.
Im gonna try it like this and if it doesn't work i guess i and do another piece and tig them together to make a half inch

cutting out circles
https://static1.pt-content.com/images/pt/2011/10/IMG_0980-1.jpg

double sided tape for the rough cut
https://static1.pt-content.com/images/pt/2011/10/IMG_0982-1.jpg

https://static1.pt-content.com/images/pt/2011/10/IMG_0983-1.jpg
using cheap flush cut bit from harbor freight
https://static1.pt-content.com/images/pt/2011/10/IMG_0985-1.jpg

https://static1.pt-content.com/images/pt/2011/10/IMG_0986-1.jpg

all done
https://static1.pt-content.com/images/pt/2011/10/IMG_0988-1.jpg

[dontlifttoshift]

nice work but 1/4 aint gonna get it done. Fix it now and save yourself the headache of having to do it later.

[Bryce]

Can you add to your bracket and tie something out of plane? I would not trust 1/4".

A 1/4" aluminum plate 6061 T6 with a 5" x 1/4" cross section and a moment arm of 5" will start to deflect .01" at the end at 150 lbs force. A 1/2" thick plate is 10 times stronger.

[hessdawg]

Can you add to your bracket and tie something out of plane? I would not trust 1/4".

A 1/4" aluminum plate 6061 T6 with a 5" x 1/4" cross section and a moment arm of 5" will start to deflect .01" at the end at 150 lbs force. A 1/2" thick plate is 10 times stronger.

so would you recommend going with a new piece of 1/2 inch or would there be similar strength with 2 pieces of 1/4 inch tigged together???

[Bryce]

I would suggest designing/building in some out of plane supports. But if you cannot do that, then I would set up to 1/2" total thickness. 1/4" plate stacked will yeild similar results.

SINCE I DO NOT KNOW YOUR LOADS OR OFFSETS OF THE 'CANTILEVER' BEAMS (PLATES) I CANNOT GIVE YOU AN EXACT RECOMENDATION.ONLY A SUGGESTION.

Good luck with your project!

[exwestracer]

The main problem as I see it is the distance between the mounting plates and the belt. The 1/4 should hold the components fine, but it will bend with belt tension. Some tie bars between the compressor and alternator tabs and the water pump bolts (the "out of plane" braces mentioned earlier) should alleviate the problem.

[hessdawg]

ended up going with two 1/4 pieces and still had some flex on the compressor side added a 3/8 aluminum rod and rod ends from the compressor to the alternator
now the compressor has no flex but the alt has a little
https://static1.pt-content.com/images/pt/2011/12/19e4eb6f-1.jpg

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