Thread: Teaser of the Week!

I was wondering if you get hold of 3" pipe bending spings. But then this caught my eye:

PVC Pipe Bending Tool 9B - Heats Pipe from the inside. For bending 1 1/4" - 3" Sched. 40 PVC Pipe - SME Inkjet Printer Cartridge Supplies and SJ 27 Oil


Just the rotten job.

Looked great.. Until I saw the price

Tape a cap on an overly long length of the PVC pipe. Fill said pipe with sand. Put another cap on the other end. Use a heat gun and with the pipe on a flat surface, bend it around a curved wooden template (that is at least 2" high for 3" dia pipe) - to the desired angle.

That'd work. I reckon. Not tried it.

Well after speaking to several exhaust shops today & not having much luck finding someone that can mandrel bend 3" pipe, finally spoke to guy tonight that may be able to help.
I need to take car down there to get measured up for correct angle of bend, so if I can finish a little earlier tomorrow will pay him visit. Still not sure whether to go for stainless or mild steel, will see what difference in cost would be. I am not too concerned as I am thinking of painting in body colour either way. They only run certain sizes/pipe types in long runs so will have to fit in to their schedule/run. However It seems they would be able to do next week if they have specs sorted in time.
I know I could get it welded but I really prefer cleaner look of bend without join so will see what $$ come in at.

Wouldn't mild steel rust from the inside out? You could buy the straight and mandrel bends and weld them up, and then polish out the welds. A lot of work polishing though.

That thought had crossed my mind, particularly if it is made up in sections & welded.
Stainless is definitely prefered option, just thinking out loud I guess.
Would be nice to get this all sorted prior to Wombat though!

Yes, it will be pretty wet I expect. Have you considered hiring a pipe bender? The hydraulic ones.

Even with the sand I'd guess the PVC may flatten out rather than hold the perfect round shape. I've sand bent a lot of steel and you still get some creasing/rippling unless you're very careful. Also make sure the sand is VERY dry and leave one end uncapped as is will displace and needs to go somewhere and it allows any moisture to escape as it can and will explode. I've seen it happen in steel with bad results and PVC is weaker (though possibly less harmful but wouldn't want to find out).

For the area an ellipse starting from the same 75mm round squished to 100 x 50.

(100 x 50)0.8 = 4000mm/\2

Area or round 75mm tube

A = (75/\2 x n)/4 = 4417.86mm/\2

So it will be slightly less but fine in reality for the engine. You won't be pulling fluid velocities large enough to build a big enough boundary layer of laminar flow to worry it. For testing I fed a 4.7 V8 with a single 60mm inlet and it was only above 9000rpm that boundary layer formation started to restrict flows, without that it would have been fine with volume restriction starting to occur at 11,750 and up (ended up feeding with 2 x 100mm, for looks).