why use a cat-track?

[knightsofnii]

I already know why a cat track is needed, but i cant put it to words to convince my buddy that it is necessary.
If any of you have 3-4 minutes to spare, can you jot down all the reasons why you NEED a cat track in a good pneumatic press?

Some people get away without it. I think its a necessity. What do you think and why?

and please if you can, try to explain also why the sequence goes top mold + airbag + cat track + steel sheet + board top, and not top mold directly over top surface of board with airbag pushing down on that?

There's lots of dudes on here with way bigger brains than mine. I know why things need to be a certain way I just suck at explaining it when i'm on the spot. Thanks.

[dg]

doug, you want to build skis or boards with different thicknesses, different profiles etc ? And you don't want to replace the top mould every time with another one precisely engineered to fit the profile of the board ?

Then you need a cat track - it's flexible down the length of the board, so adapts to any thickness changes, but stiff across the board therefore spreads the pressure out evenly from the hose.

So with a cat-track you can build a rough top mould, just to ensure the hose conforms properly to the bottom mould. My top mould (like many others) is not cambered for example - way easier to build.

I guess I had to answer this now that my press has TWO cat tracks ;-)

Dan

[knightsofnii]

yea i noticed that, can you explain the 2 cats? that's like my car having 3 catylitic converters hahaha, you trying to pass inspection?

Also I'm looking for reasons cat track system is BETTER than using a rigid top mold. My partner wanted to put our top mold directly over the board and use the airbag to squeeze it down.

[rockaukum]

If you put the top mold directly on the top of the ski / board you will have any imperfections transfered into the top of the ski/ board. One would assume you have a perfect top mold? In that case it would work but as said by dg, one mold one size only. You can build an adjustabel top mold and use the track to ensure the pressure is spread out evenly across the ski board. With the use of the cat track, your top mold does not have to be too percise, more like a filler. Then the cat track will do the rest, evening out the pressure across the project. Trying not to ramble too much.
ra

[dg]

doug - it's better cos it's more flexible !

I have two cat tracks cos I had the heavy steel one which was a pain to suspend, and replaced it with aluminium. Thought I'd use the steel one under the board as a heat transferring system and a 'provider of flatness'. So the heavy steel heats up thoroughly and gives a nice even transfer to the board, also cools nice and evenly down when I turn off the heaters. The cat track under the board is way more rigid than just the old MDF mould. I noticed it when I ground 'other Dan's' snowboards - they ground super evenly, the bases were flatter than anything I've ever made before - outstanding side effect !

[knightsofnii]

dan what are you putting inbetween the cat track and the board?

we're thinking about getting thicker sheets of steel/mdf, or just going straight to the cassette method.

i'm thinking that, although something like a sheet of hardboard, or 1/8" hard plastic will work ONCE, over time the shape of the board will become indented in the material, rendering it useless.

we tried a sheet of tip filler covering the board, but the gaps and indentures of the bars translated right through it.
I also want the cassette because if it is the same "deepness" as the thickness of base/edge, then everything above it should press down close to flat with the outside portions of the cassette, less chance of top layers bending over anything causing lift in parts, which is what we're experiencing right now.

Anyway, thanks for the help. What other reasons?

Also, heat blanket placement? We tried above the cat track, it did heat everything up but I think I pulled it too early, there was some uncured resin in spots. Maybe it works and we just need to leave it pressing for 1.5hours or something and at higher temps? I guess only time will tell but i think Dave's convinced that above the cat track is a no go.

Underneath the bottom layer would require incorporating the heat blanket into the bottom mold, which means you'd need a new blanket for every mold. I want to put it in the right spot but also keep it from being damaged by the cat track.

Another thing: should i abandon the 1" bars, and go for 1/2" bars? I think this would work out better. I also think if we fasten them right to a metal sheet via welding or screws, it would = no movement of cat track beams and ensure better pressure.

Our last board failed as a result of a number of problems I'm afraid, so identifying each problem and eliminating it is going to be a PITA

[dg]

I build the board on a stainless steel sheet, lined with baking paper (taped down to totally shield the steel). On top of the topsheet, protected by plastic film, I put another sheet of baking paper, then another stainless steel sheet. This is taped together at the ends and wrapped in the plastic sheeting which I use under the steel sheets to protect my workbench.

This package then slides between the two cat tracks and is pressed.

I prefer squishing the board between metal sheets, rather than something 'disposable' - just think it's better to avoid local disruptions, rippling etc, and easy to free from epoxy if some gets loose.

I have my lower heat blankets under the bottom cat track. I don't need a new one for each mould, I leave the excess hanging over the end of the mould in contact with the excess bottom cat track to absorb the heat.

My bars are about 25mm wide which is just under 1", think your size is fine. Mine is suspended on cables, which are not restricted - eg the bars can move freely along the cable. I just check before pressing that there are no gaps. If they can't move freely they interfere with each other - especially the alu ones as they have 'sharp' corners. I think if you weld them to a steel sheet you might be liable to interference, and if you get 'mess' on the steel sheet, dents, damage, something stuck to it - then you might have to scrap the lot. With a cat track you can replace the damaged elements...

If and when I use the upper heating system, I'd probably install it above the alu cat track (below the hose, but with an insulating layer to protect the hose). The alu will conduct into the board very well, and the heating system is integral to the press, and not some 'contraption' to lay on top and try and align once the board is in.

[dg]

The heaters are below the bottom cat track.



You can see the heater peeping out just left of the end of the bottom cat-track.

[knightsofnii]

go here:
http://www.signalsnowboards.com/shop/bo ... 0small.pdf

it takes a while to load its signal's whole catalog.
First pic is the press in action. Got any idea what is between the bag and the cat track? looks like some kind of shim for extra pressure at the tips, it just doesnt look right



Dan the double cattrack is interesting.
I think we're just going to take the plunge and have a cassette built (top/bottom). We found a local guy who can hopefully do it, provided I can get him good files.
With cassette we can lay a bag underneath and also attach edges easier i think.

[dg]

doug - check out the back page of their catalog - there you can see it's just a blue coloured sheet or something which is folding up outside of the hose - on the front cover the shadow makes it harder to see...

[knightsofnii]

ok, looks like only advantage they have over me is cassettes and top/bottom heaters...oh and probably 10+ years

We definitely need more mold cavity, and if not cassettes, then at least some steel/alu sheets with some thickness to them.

We also need molds with more nose/tail area. We're building longer boards than the molds were designed for so there's issues because the base is coming to about 1cm short of the ends of the mold. I think we need one or two new molds to close the gaps in our size range.

Thanks for all the help everyone!!

[Cadman]

That blue sheet you are talking about is probably a piece of ptex. The reason for the sheet is to prevent the airbag from scraping on the cattracks or bolster tubes as we call them. The constant rubbing of the air bag on the bolster tubes along with the heat from the upper heat blankets can cause the airbag to fail eventually. The aluminum bottom formblock is segmented. The tip and tails are on slots so when you want to change the running length, you put in a longer or shorter camber plate and slide the tip and tail block in or out. That was a design I came up with about 10 years ago for snowboards. The formblocks have a heatblanket pocketed in the long platen that the blocks rest on with an insulation plate between the platen and the press so you don't end up heating the press frame. The heat blanket never has to be changed unless it fails. Once you have the correct camber plates for your skis, it only takes about ten minutes to change to a different length. You can also change tip and tail radii if you make different radii blocks.
You can get away with changing the running length by about 10 cm before
you have to build a new upper block.