We had a race car, we had some new fiberglass bumpers, but sadly, we didn’t have a way to join the two. So, using some simple tools and methods, we made our own bumper brackets.
We had a race car, we had some new fiberglass bumpers, but sadly, we didn’t have a way to join the two. So, using some simple tools and methods, we made our own bumper brackets.
Would welding the gaps make them even stronger, or is that overkill?
In reply to pinchvalve (Forum Supporter) :
Yes, it would make them stronger, and yes, in this case it's probably overkill. Those bumpers aren't doing anything structural--they're just cosmetic and weigh very little. The brackets will outlast the bumpers in an incident.
I wonder if a contour gauge would help with fitting a curved interior?
Three words: Send-Cut-Send
I love making hammerformed sheetmetal parts. Great way to build a light, strong part.
Good article and informative. I liked the drilling of the 1/8 inch holes at the corners--makes for a reasonable corner and no stress risers either--good points indeed. It seems that brackets I make typically involve welding since they are thick and I don't have a means to bend thick steel. This hammerform method works well for the thinner metal--thanks for the good photos and explanation.
Wow .. Neat ! I've never made anything with a hammerform. Now I wanna make something ! Is there a limit to the thickness of sheetmetal used ?
I love the 928 in the background!
RoadRunnerKen said:Wow .. Neat ! I've never made anything with a hammerform. Now I wanna make something ! Is there a limit to the thickness of sheetmetal used ?
Depending on the material you use, it may start to crack. I've had this happen with aluminum but I suspect it was more the angle I was trying to bend to, being simply too much bending. Metal stretches, expands, contracts, usually all in the same job haha.
As for a limit, that is mainly gonna be a factor of how hard and how heavy a hammer you can swing. Metal brakes are a thing, but they're probably overkill for most of us.
It's really rewarding to make a good bracket out of a flat sheet of metal though. Sockets of varying sizes make good smooth angle hammer forms for simple brackets. =)
Nice to see someone is going to race a TR 7/8. Simple cars, and at one point there was an endless supply of boneyard spares. Since the Chinese sucked up all the scap steel about 20 years ago to build their Olympic infrastructuremost of the yards have gotten rid of anything older than 10 years. Not much to pick from now.
In reply to DWNSHFT :
The 928 is nice, but doesn't compare to the lovely red XKE in the background a couple photos further down!
Most steels can be bent, although with varying degrees of difficulty.
For aluminum, the main thing to remember is that the most commonly available aluminum (6061 and it's variations) is really bad for bending. It'll crack really bad. I usually specify 5052 instead, which is also pretty readily available. 3003 is another good bending aluminum.
The other main variable is the inside radius of the bend. A larger radius can reduce the amount of stress on a part. Generally speaking, the thicker the material being bent the larger the radius needs to be.
In reply to Triplesn8s :
We've enjoyed this car a lot, especially since it's been a racecar since the 1980s when the current driver's grandfather raced it. Rarely do you see a TR7 at a race anymore.
In addition to the fiberglass bumpers, the car has new paint and livery this year. It may look familiar.
I got to race a TR8 a few years ago in LuckyDog. It's a really fun little car. Light and nimble, decent brakes and surprising torque for such a small car. I'd love to try out a TR7.
In reply to te72 :
When bending Aluminum sheet, there is a minimum bend radius rule to follow. You also need to use the correct type of Aluminum. 70 Series Aluminum is quite brittle and does not like to bend. 60 series is extremely common and is less brittle, but is still not ideal for small bends. For making brackets with small bend radii, 50 series Aluminum is the correct material as it is more ductile.
In reply to te72 :
Late reply but they republished the article, so.... Yes, it's material dependent. The final "temper", in this case the amount of rolling in the steel after the most recent anneal, is very important. For aluminum, it's not nearly as forgiving, especially if you are bending parallel to the sheet rolling direction. If you have a known scrap piece from the sheet of aluminum, try bending it in two directions (along the length, and across the length) and reserve your tightest bend for the direction that survives the tighter test bend. Another way is to put a radius on your bending blocks that limits how tight the bend curve is. Some guidance can be found online, for instance https://xometry.pro/en-eu/articles/sheet-metal-bend-radius-table-calculator/
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