Building a set of Panhead upsweeps...

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Prof
Founder, Choppers Australia
Posts: 5625
Joined: Sat Oct 22, 2005 3:54 pm
Location: Willunga, South Australia
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Building a set of Panhead upsweeps...

Post by Prof » Sun Oct 23, 2016 1:50 pm

Yesterday, Rob brought down his '65 Panhead for a set of upswept pipes. We'd had some prior discussion on the phone regarding clearance under the motor and possible purchase of an OEM 'S' pipe. These are a pressed steel flattened pipe. He said he had one, so I said to come on down and we'd get things cranked up.

Panhead on stand and a rear guard sat on the wheel to give us a clearer idea of where tail pipes should finish. His guard will be bobber shorter than this standard FX guard...
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The shocks he had on the bike, were standard FX... too short (2.5" ground clearance) for this bike and very fat. Rob is planning to go with a weld on hard tail later on, so to keep the pipes in as much as possible we put on a narrower taller set of IKONs I had in stock. These brought the ground clearance up to 4" and narrowed the bike by a good two inches...
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Rob's 'S' pipe did not fit...
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OEM 'S' pipe...
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But fear not, Da Prof ain't called Da Prof for nothing! Ten minutes of playing around with some standard 1.75" pipe and I reckon we can do the job with only a small indent.

One end of the pipe needs expanding, so while I do that, Rob cuts off an awful bracket some one has welded on. We will make a nice on that unlike what gets cut off, is strong and convenient...
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Here the pipe is expanded and a small indent hammered in with heat...
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I didn't get a photo of the process, but for doing jobs like this I have made up some half pieces of water pipe to act as an anvil in the vice and support the round side of the pipe so it is not flattened.. I could have done a neater job of the indent by using a piece of 1.25" pipe instead of the hammer (two person job), so it did not end up with small dents, but it is on the bottom unseen and Rob was elsewhere...
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Arrows show where I taped some folded cardboard to simulate 4mm clearance around frame tube and also under the front engine mount. Full round pipe fits fine...
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Mitre gauge used to get angle for next piece of tube...
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This is transferred to a mandrel bend. Using the square allows me to mark the correct angle of the cut...
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This little shop-made tool shows where on the curve of the pipe the cut should be...
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Cut made and marked, so the pipe runs at a very slight upward angle towards the rear...
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Tack welded...
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Rob's new bracket welded in place. Is 8mm thick allowing for a thread to be tapped into it for a 3/8UNF bolt...
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A matching tab from 5mm flat bar is made and bolted to the frame tab. Pipe is then held in place by Rob while I tack weld the tab to the pipe. Hole in the pipe tab is drilled to 12mm to allow movement for final alignment of the pipe...
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Part of the process is making sure we will end up with bottom and top tailpipes parallel adn clearing the shocker...
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Front section of pipe now. Expanding to fit the head first. Test piece in background...
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Front works well with a 90 degree mandrel bend at the bottom that slips into our 's' pipe. Top piece requires only a very short section of the bend. To get the correct lengths for proper alignment, I started off 10mm too long and gradually cut back until the ends lined up perfectly. It would have been nice to have done a gradual curve instead of using a mandrel bend for the top piece, but heating and bending requires filling the pipe with sand and welding off the ends before bending... all of which takes about three or four times longer... something that did not fit into Rob's budget...
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But looks great from this angle anyay...
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Now to the rear pipe, beginning with an expanded straight section...
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A 90 degree bend gave us the right upsweep and almost cleared every thing. Once the two pieces were welded together and linished back, we heated and bent the pipe close to the expanded end. White line shows slight bend that was needed...
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Checking for clearance at shocker...
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Prof holding the bottom pipe at same angle to see if Rob approves. He thinks it looks great...
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Wooden spacer made up to keep pipes parallel while we set up the final bend for the bottom pipe...
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Mandrel bend is cut through the curve as with the earlier example shown and tack welded in place...
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Everything looks great, so all pulled apart for final welding on linishing.

When a tube is bent in a mandrel bender it shrinks slightly. Simplest way to overcome the difference when welding on the straight piece is to; 1. line up the side that will be seen and tack, 2. Slot the end of the straight pipe, 3. tap in with a hammer, 4. Weld join and slots. Make sure your weld penetrates right through the tube or it will be thin and week when you linish off the excess...
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Linished and installed...
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The new look, fish tails and all...
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Builder and owner both very pleased with the end result... looks really killer. Rob was contemplating a 5x16 front wheel, but has decided to keep the 21 incher as the bike now looks so complete.

If you look closely at the forks you will notice someone has installed the rockers upside down. Rob will set them up correctly which will add another 1.5 inches ground clearance at the front.

Another happy customer.

And I hope this post will gives you blokes who like to play in your workshop, the encouragement to have a crack at doing up your own pipes... the sky's the limit... ah! Now talking about the sky how about a set of birdshooters! Well, keep watching as we will be doing a set for the GSX 750 we are currently building for James.
Chopit'nrideit... Prof

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