I was watching one of the how-to auto shows (Bitchen Rides I think) the other day when the exhaust tube donut (above) showed up. I remember seeing them a long time ago but not since. They were working on a '32 Ford highboy roadster that this guys wife had fallen in love with. The guy bought it for her but it needed some work done (a lot of work in reality!!!). Part of the problem was the steering and front axle and this is where the donut came into play.
They had to build a new steering system and when through with that they had to re-do the exhaust pipe in the area. The donut showed up and the mechanic copied the inner and outer dia.s' of the tube on cardboard then quartered it (all done by drawing lines on the cardboard). He then divided one quarter by drawing lines that looked to be close to 10° apart but could have been less than 10°. He then cut the marked quarter carboard section out and used it and the lines to find what angle of the bend was needed in the vertical bend direction. He then used another piece to figure out the horizontal bend around the steering and then the connection to the straight exhaust. The welds were done and the fit and look were great.
For what it is worth...
Lee
Corrected the word sense to since which is the proper spelling and meaning for what I was trying to say.
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Last edited by Ol'fogasaurus on Tue Jul 09, 2019 9:13 pm, edited 1 time in total.
One or more! Commercial bends that are available are pretty much fixed to 90, 45° and maybe 30°. You can cut them into smaller pieces to joggle around things or things around ( ) which is pretty common to do; I've seen it done here by the turbo guys (good job guys) but this is another way of doing the same thing.
You can get other bend angles if you have a tube bender assuming it is a proper tubing bender for cages or exhaust (the other type can work I guess but at a certain point you can start to get oval-ling of the tube mainly because of the angle or radius. This way you can make any angle you want and have less scrap afterwards assuming you are not making a single 360° bend and have an inlet and multiple exhaust outlets in it (giggle, silly me).
I said I thought the lines on the mockup were about 10° a part but I think it was closer to between 2° and 5° as there was quite a few lines from the center point of the circles. !0° would add up to 4 1/2° lines so I am embarrassed over this . Anyway, as I told Jadewombat they are another thing that if found could be used to an advantage.
I'm pointing out the dimensional issues when using this method:
If a angle is cut ; and not mated with the the exact angle, the diameter of the pipes will not match and will leave a gap. Let's say you have a 2" pipe that measures obviously 2" in diameter. If you cut it at a angle, the distance is going to be more than 2" now. Basically it's a diangle.
theKbStockpiler wrote: ↑Tue Jul 16, 2019 7:04 pm
I'm pointing out the dimensional issues when using this method:
If a angle is cut ; and not mated with the the exact angle, the diameter of the pipes will not match and will leave a gap. Let's say you have a 2" pipe that measures obviously 2" in diameter. If you cut it at a angle, the distance is going to be more than 2" now. Basically it's a diangle.
Good obversation and it is very true! I'm pretty sure that is why the marks on the cardboard donut were added so the angles of cuts matched so when they were joined by tape (in the TV show) prior to tacking there were no gaps and the arcs looked to match up smoothly when welded.
Thanks for pointing that out as it is a important fact that I missed to point out.
I too wanted a easy and economical way to get mandrel results but after studying it , I had to conceded that I was %#?!-ed. I looked at a lot of pipe bender hacks and to me the possibilities are not exhausted. I want to try to weld tall walls on a pipe bender die and see if that would help. I don't have the time for it right now though. I watched some Utube vids on the subject and some of the posters have ways that are close but not perfected enough.
theKbStockpiler wrote: ↑Tue Jul 16, 2019 7:47 pm
I too wanted a easy and economical way to get mandrel results but after studying it , I had to conceded that I was %#?!-ed. I looked at a lot of pipe bender hacks and to me the possibilities are not exhausted (pun accepted). I want to try to weld tall walls on a pipe bender die and see if that would help. I don't have the time for it right now though. I watched some Utube vids on the subject and some of the posters have ways that are close but not perfected enough.
Pipe benders have drawbacks one of which is that is they need extra material to hold onto in order to form the bends and which can result in the bends are pretty much limited to how close together the even small bends can be hence the common whacking away and joining pre-bent tubes or the donut way of achieving tight or multiple bend tubing runs (exhaust isn't the only use for this type of bends either). Another thing is that mandrel bent tubing isn't always round but can be slightly oval (unless they are filled compact before bending and even then...).
I have done some heat bending thick walled square tube but that was back in the '90's and there are still limitations to that way of bending also.
Lee
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I have used a few donuts in my build. I like them. Tighter radius than you can get in a mandrel bent tube. I have found that sometimes they aren't very round though. I've bought in 2.5 inch and 2 inch. Very useful.
I have to correct my statement on the angle being off. The issues is the doughnut is continually angled so when it's connected to a straight piece the two pieces don't transition well. If you look at jobs that used the doughnuts you can see at where they meet with straight pipe that the mating is off. There's always some sort of compromise.
theKbStockpiler wrote: ↑Thu Jul 18, 2019 9:52 am
I have to correct my statement on the angle being off. The issues is the doughnut is continually angled so when it's connected to a straight piece the two pieces don't transition well. If you look at jobs that used the doughnuts you can see at where they meet with straight pipe that the mating is off. There's always some sort of compromise.
As I said somewhere else... there is always a tolerance and having tolerance to the tolerance is a necessity. Intolerance is not a worthy thing to have when dealing with inanimate objects .
) which is pretty common to do; I've seen it done here by the turbo guys (good job guys) but this is another way of doing the same thing.
and have an inlet and multiple exhaust outlets in it 
