I have just bought a new Wren single wall pipe and the latest diagram has dimensions for an outer pipe. The diagram suggests to make this out of lithoplate and I was told that it could be simply bolted together to make a pipe.

Has anyone made an outer pipe with a Wren inner? How did you do it?

If I use lithoplate what thickness do I need and where do I get it in the UK? Would I be better off getting an outer pipe made professionally?

interesting im just fitting a Wren pipe inside the outer pipe of my FlyEagle F16, after all the scare stories of there pipes giving up i broke off all the spot welds and removed the inner pipe, plus being that the pipe is designed for the supersport, bloody fiddly job though

lozza

I fitted a wren pipe in a .10 staniless outer and once all the gaps were right it worked very well both in static thrust and in the air. The outer pipe was made by BVM for the AFS F-86.

jason

I made a litho outer pipe for my SuperSport pipe.

I rolled it around a bit of slightly smaller plastic drain pipe to get a nice tube with about 10mm overlap.
I used pop rivets & some silicon to make the join.

The tricky bit was supporting it. At the back it overlaps the cookie cutter rear pipe mount & at the front it rests in a hole cut in a former holding it an even distance from the pipe which is, of course, supported by the straps. I pop riveted a tiny piece of aluminium angle on it to stop it sliding forward.

I followed the instructions with the Wren pipe for dimensions & spacing.

Having said all this I have not run the engine in this plane yet. I hope it all works! [sm=72_72.gif] - John.

Don't understand why you guys are doing this.....though I did miss the horror stories someone referred to above.

Most pipes I'm familiar w/ are double wall from 1/3 to half-way half way down; WREN's just use a much shorter section (maybe 3" long....the 'cookie cutter') that slides over the (inner) pipe end; this way the inner pipe can be cut to optimum length. The CC rear edge should extend a half-inch or so beyond the end of the inner pipe edge to promote venturi-type cooling. Front/bell, centered, and affixed w/ the four straps approx 1" behind the engine rear exhaust nozzle edge. Inner pipe is robust, installation is quite secure. But that gap of one-inch is most important...infact WREN says 30mm (about 1-3/16")...otherwise, the pipe might collapse being, starved of secondary air. Inner pipe then rides in the CC during expansion/contraction....CC can be affixed/held positioned by a rear wood former, etc. I've used two short 2-56 SS screws to either affix CC to the inner pipe so any sliding needed is the CC in the former. Or, SS-screw the CC to the former; inner pipe slides in the CC. That part....the drilling/screwing is, indeed, a bit tricky.

Pipe runs cool....both Golds and SS. Unless you have some very minimal clearance in the rear fuse, say, less than half-inch distance from combustibles.....why are you fashioning a full length outer wall? What are those 'scare stories'? Tx!

Ray

Hi All, unless I have been really lucky I have never used an outer sleeve with my wren pipes. I have a Flash, BVM Sabre Mig 15 all were just wrapped in ceramic blanket (supplied by Wren and never had an issue with excess heating. Ron

Never use an outer, never a problem, Wren pipes a very good, extra thrust and run cooler than most.

Paul

I've never had a RX battery fail but I still use 2! If a weld on the inner pipe let's go them my model is toast. I am also worried about the possibility of a servo lead coming adrift and resting on the pipe. I'm guessing (although I don't know) that I am more likely to get away with this if it rests on an outer pipe. It just seems like cheap insurance to me.