Often when you’re focusing on cars you do have a must form tubes with bends, depressions or any other shapes within them. You might be working on carbon steel oval tube, intercooler plumbing, a cylindrical airbox, and even heater or turbo oil drain plumbing. Exactly how do you form these bent pieces of tube?
Should you be making something similar to an exhaust or intercooler plumbing, buying pre-formed bends then joining these is the most effective way to go.
The bends – best are mandrel bends where the internal diameter remains constant – can be found in steel, stainless or aluminium. An exhaust should use the steel or stainless bends, while intercooler plumbing can use any one of the three types of metal.
Joining from the bends may be completed by welding – MIG, TIG or gas welding in the matter of both steels, or TIG with regards to the aluminium bends.
When you don’t use a welder, tape the bends together after placing ‘witness marks’ (where you have used a marker to run a line down the pipe and all over the join, showing the way the bits align) after which consider the assembly to some welder.
Mandrel bends can be purchased in a range of angles (eg 15, 45, 90 180 degrees) and diameters from about 1.5 inch to 4 inches.
When coming up with plumbing using these bends, ensure you:
Work with a friction saw with a large diameter blade to cut the bends to length. Don’t try using a hacksaw – it is almost impossible to create a cut which is sufficiently straight it might be easily matched to another bend.
Do not cut the bends anywhere except where they can be straight – cutting in the bend itself will reveal a wall thickness thinner compared to unbent tube (since the wall has become stretched) so the weld is more prone to intrude as well as the join will probably be weaker than whether it were made in which the tube is straight.
Should you use mild steel bends to form intercooler plumbing, the very last result could be blasted, undercoated and then powder-coated to get a durable and professional final result. Stainless steel or aluminium may be polished.
The advantage here is you can make the bend the actual required angle, as an alternative to being restricted to the angles in which preformed bends are offered. The downside is except if you have a really expensive mandrel bender sitting in your house workshop, the bends may have a qualification of crush and you may get some wastage before you get a bend you’re completely happy with.
Generally it’s not truly worth trying to produce your very own bends in large diameter tube. A oval tube that utilizes a hydraulic jack and curved tooling is designed for heavy-wall pipe and definately will give poor bends in thin-wall tube. (However, in an emergency you might be able to pull off sand-filling the thin-wall tube – see later.)
However, small diameter tube may be successfully bent with a hand bender such as this one. It arrives with dies to fit 3/8 inch, ½ inch, 9/16 inch, 5/8 inch, ¾ inch and 7/8 inch (most tube sizes are imperial).
Here is a piece of 5/8 inch diameter steel tube bent with a hand bender such as that shown above. It is an oil drain pipe for a turbo.
If you want to gain some clearance, it really is possible to ‘ovalise’ round tube – even when you use a preformed bend.
The key is to fill the tube by using a coarse sand prior to starting to reshape it. The coarse sand has lots of voids between your grains that can progressively close-as the tube is squashed. The actual existence of the sand resists the change fit, giving the tube more support so preventing deformation from the wrong directions.
This 2.5-inch mandrel bend was applied as a turbo dump pipe – it’s shown here after being ovalised. It absolutely was ovalised for two reasons – firstly, the oval shape matched the exhaust dexopky14 from the turbo, and secondly, the oval shape needed to continue down the tube to provide 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 first filled with coarse river sand. Remember that if you intend heating the tube (eg with the oxy) the sand has to be absolutely dry. Here the sand is shown within a cast iron baking tray drying out over a wood stove.
After being full of sand, the ends in the tube were capped with aluminium foil and tape. Contrary to first thoughts, the final caps aren’t under a great deal of pressure – the sand doesn’t flow along the pipe that easily.
The sand-filled pipe was then put into a hydraulic press. Two hefty components of flat timber were placed above and underneath the pipe, using a steel plate placed underneath the press’s ram. A clamp was applied to prevent the arms of your bend spreading as being the ovalisation occurred. In this instance the work was done with no tube being heated.
The pipe will endeavour to form a figure-8 cross-sectional shape because it is being compressed; the outer edges might be pressed separately (as is also occurring here) to decrease their height as required. Note the usage of the timber block – this deforms just a little and spreads the load. Consumption of a metal plate straight around the tube will often dent the tube.
Make certain you look into the sand level during the pressing process – since the grains are crushed together, the amount can drop.
For those who have a requirement for clearance at only one spot, you can place a depression in the wall of your tube. As was described above, ideal results occur if the tube is first filled up with sand.
This corrugated stainless steel pipe needed a dent placed in its wall to provide adequate clearance into a starter motor solenoid. The dent was put into the tube (ex truck exhaust tube) as the first step once the tube was cut to length.
Keep in mind that this approach gave a far neater result than utilizing a ball-pein hammer and forming the depression by traditional panel beating techniques.