Often when you’re focusing on cars you have a need to form tubes with bends, depressions or other shapes within them. You could be taking care of carbon steel oval tube, intercooler plumbing, a cylindrical airbox, or even heater or turbo oil drain plumbing. Exactly how do you form these bent bits of tube?
When you are making such as an exhaust or intercooler plumbing, buying pre-formed bends after which joining these is the best way to travel.
The bends – best are mandrel bends where internal diameter remains constant – can be bought in steel, stainless-steel or aluminium. An exhaust should take advantage of the steel or stainless bends, while intercooler plumbing can make use of some of the three kinds of metal.
Joining of your bends can be carried out by welding – MIG, TIG or gas welding when it comes to the two steels, or TIG in the case of the aluminium bends.
In the event you don’t have a welder, tape the bends together after placing ‘witness marks’ (the place you used a marker to perform a line along the pipe and across the join, showing just how the bits align) after which use the assembly to a welder.
Mandrel bends can be found in an array of angles (eg 15, 45, 90 180 degrees) and diameters from about 1.5 inch to 4 inches.
When making plumbing using these bends, ensure that you:
Work with a friction saw by using a large diameter blade to slice the bends to length. Don’t try using a hacksaw – it is actually extremely hard to produce a cut that is sufficiently straight it might be easily matched to a different one bend.
Try not to cut the bends anywhere except where they are straight – cutting about the bend itself will reveal a wall thickness thinner compared to unbent tube (because the wall continues to be stretched) and so the weld is very likely to intrude as well as the join is going to be weaker than when it were made where the tube is straight.
If you use mild steel bends to form intercooler plumbing, the last result may be blasted, undercoated then powder-coated to get a durable and professional result. Stainless or aluminium could be polished.
The main benefit here is that you could make your bend the particular required angle, instead of being restricted to the angles by which preformed bends are available. The downside is until you happen to have a very expensive mandrel bender sitting at your residence workshop, the bends may have a college degree of crush and you might have some wastage just before getting a bend you’re completely pleased with.
Generally it’s not worth trying to form your personal bends in large diameter tube. A oval tube that utilizes a hydraulic jack and curved tooling is for heavy-wall pipe and will give poor bends in thin-wall tube. (However, in desperate situations you could possibly pull off sand-filling the thin-wall tube – see later.)
However, small diameter tube could be successfully bent having a hand bender such as this one. It comes with dies to accommodate 3/8 inch, ½ inch, 9/16 inch, 5/8 inch, ¾ inch and 7/8 inch (most tube sizes are imperial).
What follows is a part of 5/8 inch diameter steel tube bent with a hand bender like that shown above. It is really an oil drain pipe for a turbo.
If you want to gain some clearance, it is possible to ‘ovalise’ round tube – even when working with a preformed bend.
The secret is always to fill the tube using a coarse sand before beginning to reshape it. The coarse sand has lots of voids between the grains that may progressively close-up as the tube is squashed. The existence of the sand resists the modification fit and healthy, giving the tube more support and so preventing deformation within the wrong directions.
This 2.5-inch mandrel bend was applied as being a turbo dump pipe – it’s shown here after being ovalised. It was ovalised for two reasons – firstly, the oval shape matched the exhaust dexopky14 of the turbo, and secondly, the oval shape required to continue across the tube to supply clearance to the alternator and steering tie rod (shown in its worse position of maximum suspension droop and full right-hand lock).
The bend was basically filled with coarse river sand. Keep in mind that if you plan heating the tube (eg with the oxy) the sand must be absolutely dry. Here the sand is shown in a cast iron baking tray drying out across a wood stove.
After being loaded with sand, the ends in the tube were capped with aluminium foil and tape. In contrast to first thoughts, the end caps aren’t under a lot of pressure – the sand doesn’t flow over the pipe that easily.
The sand-filled pipe was then placed into a hydraulic press. Two hefty items of flat timber were placed above and underneath the pipe, with a steel plate placed underneath the press’s ram. A clamp was used to prevent the arms of the bend spreading since the ovalisation occurred. In such a case the work was completed with no tube being heated.
The pipe will attempt to create a figure-8 cross-sectional shape because it is being compressed; the outer edges may be pressed separately (as is also occurring here) to decrease their height as required. Note the usage of the timber block – this deforms a bit and spreads the load. Usage of a metal plate straight on the tube will usually dent the tube.
Ensure that you look into the sand level during the pressing process – because the grains are crushed together, the amount can drop.
When you have a desire for clearance at just one spot, you can place a depression within the wall of your tube. As was described above, ideal results occur when the tube is first loaded with sand.
This stainless steel gas pipe needed a dent positioned in its wall to supply adequate clearance to some starter motor solenoid. The dent was placed into the tube (ex truck exhaust tube) as the first step once the tube was cut to length.
Remember that this strategy gave a far neater result than using a ball-pein hammer and forming the depression by traditional panel beating techniques.