Cutting the pipe

[worley]

Hey guys,
I've had several attempts at cutting the main pipe that the mesh goes into, and I'm having real trouble trying to get a clean, straight, evenly spaced cut all the way along.
I've tried using several different cutting wheels on my Dremel, and also a mini bench saw used for craft projects.
Anyone have any tips?
I have a fair amount of spare pipe to test on, and it's dirt cheap anyhow.

[Sly]

It helps if you draw a line on your pipe first before you cut it. I used CPVC pipe which already had a line drawn on it but you can draw one yourself on PVC with a straight edge and a sharpie...

I set the pipe down onto some carpet and held onto it with one hand. Then I took the dremel and held it horizontally with the other hand and ran it at full speed. I gently set it down onto the pipe right at the line and let it slowly sink through the pipe. Once it was through I slowly pushed the pipe along the carpet, cutting it down the line with the dremel. It's really similar to how a saw mill would rip a piece of lumber. When I was done the line was perfectly straight and even...

[SantaMonica]

I drew a line too, and made a soft pass with the dremel to mark it, then another pass to cut deeper, then another deeper, etc. That way the wheel did not stay too long in one spot, melting the plastic.

[worley]

Thanks guys, I'll try cutting it like that this time. Will let you know how I get on :)

[worley]

Thanks again guys, I marked out the line on the pipe again (new piece), then held the dremel horizontally and put it on about 3/4 speed, let it gently cut down into the pipe, pushing it gently to ease it in, then slowly pulled the pipe towards me and it worked brilliantly.
There's no splashing at all now and pretty even flow over the whole mesh. :D

[worley]

Well after some growth, there is now little flow in the middle and lots on the sides.
This is because the plastic pipe I'm using "curls" when cut, so the initial cut is fine, but as it gets longer the plastic curls in on itself and "pinches" the mesh, reducing the water flow in the center.
I'm going to try a few different types of plastic, I've been told by a friend that certain types don't do this, but he can't remember which.
I'll give PVC and ABS plastics a try next. It looks like the type of plastic could be quite important to producing nice, even, water flow.

[worley]

Looks like it was polypropylene I used last time that curled when cut. I'm going to try some MUPVC pipe this time from one of the local plumber's merchants.

[worley]

Bah, looks like ABS plastic comes in 40mm size, yet "40mm" UPVC pipe is actually 43mm, and only works with glue welded fittings.
I happen to have a bunch of glue welding fittings + upvc glue left over from the shop days, but nothing to fit the feed pipe from the pump to the UPVC pipe. I guess it's another trip to the plumber's merchant tomorrow first thing.

[SantaMonica]

Everyone just uses regular pvc. Never curls. Hard to cut, though.

[worley]

I can definately recommend not using ABS, will let you know how the MUPVC pipe goes (it says 'EN1566 PVC-C "B"' on the side)

[worley]

Well, it was a lot easier to cut:
[attachment=1:3mncyk01]TOM_3874.jpg[/attachment:3mncyk01]
The new one is on the one on the right (duh!)
It didn't have the problem of the first plastic, where it melted behind the cutting wheel, the PVC-C seems to withstand higher temperatures and is slightly more rigid.
It did, however, pinch a little in the middle, so I simply ran the Dremel down the whole line again and it came out much more even.
I can now happily say that I've got nearly perfect even flow over the whole mesh, with virtually no splashing, it's completely silent, and now very few bubbles in the water (that were occurring where the flow was highest).
I've now cemented (with glue) the fittings together, and made a slight design change, by adding a 90 degree angle on the end so that the pipe doesn't kink (which it was when coming out from the side of the main pipe):
[attachment=0:3mncyk01]TOM_3875.jpg[/attachment:3mncyk01]

[Patrick Pending]

I scored a line along the pipe then drilled small holes all along the score line and cut the slot with an ultra-fine dovetail saw. So my screen is gripped by a a sort of postage stamp serration on each side. My reasoning was, that a straight slot might clog with algae and reduce the water flow. In practice I have found that even the serrated slot clogs with algae :roll: I think I need to shield the slot from light to stop any algae building up and blocking it. This system needs to run for at least a fortnight, unattended, when I go on holliday.

Cheers,

Pat. Pending

[worley]

Hi there,
Yeah, it may be a good idea to shield, say, the top inch of the mesh from light if you're going away for a few weeks, that should stop most of the growth from blocking it up and causing any splashing.
Let us know how well it works.
Tom.

[nm983]

Here is what I did to get a clean slit:

1 - cut a narow slit clean as possible.
2 - using a file thick as you want the slit to be go over the first slit.

this will result clean and accurate cut.