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Old 05-05-2013, 09:05 PM
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Need a bit of help with Kevlar

The race car guys want just a little repair on a ballistic blanket. Technically called a "blower bag". It wraps around the supercharger. Normally they would just send this in to the mfg. for repair but they need it right away and it takes about a month to get it back.

It will only be a temporary repair to get by the summer races.

This thing is just under 1/2 inch thick and has muliple layers of Kevlar with a Nomex inner and outer layer. It is pretty stiff too. I think it will fit under the arm of my Consew 226R and the foot will just clear when up.

What has happened is the edge binding has come loose in several spots and is fraying badly. The threads are pulling out very easily...almost like a zipper. There are also 2 holes that are about 1 1/2 inch diameter that had a binding but it is completely gone so this just need to be sewen all around. Maybe twice.
Also a sculptured area about a foot long is missing the binding and fraying.

I think somebody put some super glue on the edge to stop the fraying but it didn't work.

The repairs are not a safety issue, just to keep the thing together.

It would be nice I suppose to get some Kevlar thread but just getting some might be a problem and I'm sure it is expensive. All I have is 69 polyester bonded and some 69 nylon bonded. I can get heavier thread just down the street.

How about needles?? I don't have anything special now just the needles you recommeded earlier. I can't even remember what they are without going back in the posts. 135 x 17 plus a point style I think.

They have an out of date blanket that is a real mess. I tried to cut a piece of the Kevlar with the shop scissors and it was nearly impossible.

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Old 05-06-2013, 08:15 AM
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You can sew heavier thread ( up to size 277 which is about 4 times thicker than size 69 thread) with a size 24 or 25 needle. 1/2" thickness it at the very limit of your sewing machine's thickness cabability, so be careful.

No one lives forever, the trick is creating something that will.
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Old 05-14-2013, 06:10 PM
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Devil's advocate here.

Blower grenades. Bag fails. Pieces fly into a spectator. Spectator injured permanently, disabled, or dead.

I guarantee, anybody that has touched that safety device will be subpoenaed, sued, tried, and quartered. Maybe even tarred and feathered.

Be careful
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Old 05-14-2013, 07:58 PM
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I forgot to update this request.

Thanks Dan for your help. I even dug thru some of your tutorials for additional help.

Turns out that the bag is heavy duty nylon belt type material rather than Kevlar as I was told. it is very dense however. The outer layer or skin is Nomex.

I also found that the bag itself does not require certification. Only the belts are certified and can't be modified. The belts actually go over the the injector hat and attach to brackets bolted to the headers. There is another strap that ties the back to the top of the belhousing. There some loops on the bag itself that the belts go thru. The bag is to contain the major pieces if a blower explodes. They do a very good job of this so most of the pieces are easily contained. It takes an incredible bang just to get the whole thing to come off the motor let alone go flying.

Anyway. I cut a good size piece of Nomex and carefully folded it over like Dan showed on his carper tutorial. Then I sewed it around the first hole like a patch. I cut a small hole in the middle and poked the balance of the material thru. The material was a bit stretchy almost like Lycra so I was able to stretch and shape it around the hole. Once I got a couple stiches in it was pretty easy to work it all the way around. The biggest problem was that the bag is quite stiff and has numerous large buckles and belts attached to it so stuffing it under the arm of the machine was touch and go. I made 4 laps around the holes, the same as the other openings had.

There is a very large belt that wraps completely around where these hole are so I don't think structurally it was weakend. Besides there are a couple of much larger holes factory made that are much larger and they have less reinforcement.

Thanks for your concern.
I do quite a bit of work on these cars and have been around them most of my adult life. There are many safety devices and equipment that carries certification tags. These must not be modified so they are "hands off". Believe me this stuff is thouroughly monitored at the tracks. We have the big rule book on the bench and read it over before we tackle something like this. There are very strict construction guidelines for these race cars and if a modification is not approved, you don't get to don't get your entry fee back either. Needless to say we are very carefull.

I found that the new 3/4 hp Reliable servo motor was just barely able to do this job. At very slow speed required to go around the hole (at least for me) it had a hard time getting started. As Dan stated a while ago the hand wheel has a purpose. To really do this I think you would need a 1 hp motor and a smaller pulley on the motor for more gear reduction and starting torque....even though the servo is supposed to have full torque at startup.

Before I started on this I took a piece of cargo strap from one of my big tiedowns and folded up up to simulate the "bag". The strap was very dense and 4 layers was all I could get under the foot. Even a new needle had a hard time piercing this on the first stroke after my first stitch by hand. Once it got going and at some speed over very slow it was ok. After turning a corner with the needle down I had to help it get started, then it was ok up to the next corner.

If this had been Kevlar as I was told I don't think the Consew would have been able to do the job. Not on this thick of material anyway.

A final note at the first DRO meet this year a couple weeks ago this car qualified number 1 on the first attempt. All new motor and all new crew.
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