**Tech week** How to make a bumper

This is the method I use to make new bumpers or overriders. It can be done entirely by hand and no special machines are needed.

Here is a bumper that is past its best rotten from the inside as well as the out, its been re-chromed at least once and is beyond repair.



This bumper is made from 16g steel but I have done the same thing with 14g and 12g. (I will show some examples later)



The first thing to do is to draw around the bumper with a marker pen onto the sheet steel.



I then add extra material all round to give me enough for the radius and a little to spare.



This is beaten into a 'stump' using a large hollowing hammer. you have to work on the deepest part of the shape and remember that you are working on the inside of the panel.





The metal will gradually take on the shape you need.



The deeper the area the harder and more often you have to hit it, graduate out to shallower areas. You will notice that the edges will pucker this is what you want.



The puckers are hammered into themselves over a 'stake' or 'post dolly' (US). The puckers are locked into the metal because of the shape made by hollowing so the puckered area will shrink as it is dressed down. I use a flipper for this (= slapper- US)



It takes a fair but of planishing and it is usually necessary to hollow out some places again to get a smooth panel that fits to the original bumper.



Once one side is done, you have to do the same thing for the other. Here I am marking off the bench to get a straight line to work from, I then sand the two halves so that they fit over the original bumper with a double material thickness gap. When the two parts are welded together they will be pretty close to the original in all dimensions.



More soon...

David

 

Nice!
What does it mean to "hollow out some places again to get a smooth panel that fits to the original bumper."

 

I showed a 'hollowing' hammer and a 'stump' the stump has a hollow in it and the metal is beaten into this to create the shape as shown in the photo sequence above. MY stump is actually a bit of old railway sleeper - nothing special.

David

 

This will be a great forming tech!
Odd note: I got down to the picture of the hammer and immediately thought "Hey! this guy is English!", scrolled up and verified...
Hammers of the World on the HAMB!

 

slick idea.

 

Thanks for your interest so far guys and for the nice comments. I will post some more ASAP.

David

 

Nice work David. Hammering out 12g must be a workout.

 

That's damn neat! Simple idea!


Posted from the TJJ App for iPhone & iPad

 

It's called tuck shrinking...it's a whole lot easier with 20g sheet metal!!!

edit= Great job by the way!!

 

Mind over matter, brilliant

 

I get the lumpy dished out shape with no problem, I just have trouble getting to your finished smooth state. Nice work.

 

Impressive.

 

very nice.

 

Thanks Mindover, Yep, diggin' this, also what Walker said...

 

Wow, you make it look easy! Great work.

 

Thank you all very much for your nice comments.

David

 

we call it blocking.

good work mindover ....the old school way ...

 

Thanks!.

Sorry but its not tuck shrinking, it is hollowing. With tuck shrinking you form a 'tuck' with a tool which is called a tucking fork in the USA, we also call it a puckering iron sometimes here in the UK.

Its not stump shrinking either, which is something similar but they hit it once then flatten the pucker and do the same again, a method only used in the US.

David

 

A magazine once wrote an article about some of my work and the title was "Mind over metal". I just used the mindover bit, so you were close!

David

 

Hollowing uses a hollowing hammer which has round faces, blocking uses flatter faced hammers for flatter shapes but pretty much the same thing. At least that is how I think of it and from reading books from the past. It also may be a regional thing.

David

 

....ok in Coventry we call it blocking,i guess essentially the same thing.good job.

 

Its what you get used to I guess, I am not built like a bodybuilder. It keeps you fit I guess. The thicker the metal the heavier the hammer used.

David

 

Here is a photo of the 'stake' and my flipper (slapper)



As I showed earlier the puckers are dressed out over the stake using the flipper. The metal is held so the puckered edge is off the dolly as it is hit, this will cause the metal to pucker more and take on more shape as it is gradually dressed to the desired shape, this process is called 'raising' These two processes together are known as 'hollowing and raising' in sheet metalwork and coachbuilding here in the UK.

As a note of interest wheeling machines are sometimes called 'raising' machines.

more soon.

David

 

This compares the two halves once part formed and put together, still some smoothing and trimming to do at this stage.



All the smoothing was done by planishing in the stake by hand. Its not as hard as it may seem. the knack is to use the weight of the flipper, which is a well balanced tool and not try ti put too much force behind each blow but rather to use many light blows.

Once smooth each part is laid over the original and the perimeter lines marked onto the new panels, once this is trimmed the parts are ready to be welded together...



You can see a comparison with the original bumper in the photo above.



I use gas welding and once the two parts are welded together I re-melt the build from weld penetration on the inside of the bumper, this gives me a pretty much flush weld on the inside and no grinding to do. (too difficult to get inside) This makes it easier to metal finish the outside of the bumper because there are no lumps and bumps that could push through the panel and mark the outside when it is being planished smooth.



more soon...


David

 

awesome!

 

David, do you have anneal the metel either before, or during the work?

Thanks for posting.

 

Hi Jonnod, This is mild steel, mild steel does not anneal. It is in a soft state when you buy it, it is low carbon so will not work harden easily, it is very malliable. I do not do enough to the metal making these to work harden the steel. It is possible to work the metal hot but I do this cold. Its not that difficult.


Because I don't use thicker steels regularly I tend to have zintec sheet which will keep better in storage, that is what this material is. (it has a very light coating of zinc) You have to take a bit of care with the fumes when welding it but its not like welding galanized.


David

 

Clean. Sir

 

That's a great idea. Great work, as usual!

 

Thanks for commenting guys. I appreciate it.

I should have said that in the photo above showing the weld, it is the inside of the bumper- on the left is the penetration and the right side is after I had run back over the weld.

David