Archive for November, 2011
Here’s what the part started out looking like:
How I designed this part was that I needed the part to end up being 2 1/8 inches wide. With it being made out of 1/8 inch plate, this would result in a 1 7/8 inside dimension. Using a formula I found on the web
Bend Allowance = Angle * (Pi / 180) * (Radius + K-Factor * Thickness)
I needed to bend the material 90 degrees and using a 1/4″ radius of 1/8″ thick material. Using these values the formula looks like:
0.278 = 90 * (3.14 / 180) * (.125 + .42 * .125)
Where 3.14 is the value of Pi, 0.125 is the decimal value of 1/8″. I’m using the inside radius of 1/8″ and material thickness of 1/8″ and using the K-Factor of .42. K-Factor is the portion of the material where there will be stretching or shrinking.
Solving for this results in a distance of 0.278 inches. This is close to 9/32 inches or a little bit more than 1/4 of an inch.
How I refected this in my drawing was that I drew the inside shape, then added the bend allowance and then drew the side shape. Because I don’t have a press brake and this piece is about 5 inches long, I made a 1/8 wide cutout and left two tabs about 1/4″ wide.
This allows me to bend the part by hand and then weld up the edge. Here’s how it looks as I start to bend up the part.
Flipping it over I can bend up the other side.
All that’s remaining is the top part. Here I didn’t make a relief cut, I should have, and I did put in a relief cut for the side radius, but I put it a bit too high so it didn’t really help me make this bend. After a lot of hammering here’s what the part looks like.
Here’s how the part compares to the original:
After I was done with welding up the part and grinding the welds, I wanted to see how close I was to my original specs. I got the radius spot on at 1/4 inch, but I’m about 1/8 inch too wide. It doesn’t matter for this part, but I’ve figured out where I’ve gone wrong with my measurements and I’ll correct it in my TurboCAD drawing.
This is the 2nd project I started. I drew 3 different versions of this part to be cut out.
The top version is designed to be bent in a press. In this part I’ve used the “bend allowance” to locate the two holes in the side wings. The two holes that are vertically aligned, these are the holes that bolt to the frame rail. The cab will bolt through the holes in the wings. These holes in the wings need to align perfectly.
The first version I’ll bend up to see if I measured it correctly. The second version without the holes in the wing, I’ll just bend up, and then drill the hole through the two side pieces. This way I’ll make sure the holes line up.
The third version is a weld up one and that’s the project I did next.
Here I’ve layed the part out on my worktable. The side pieces are held upright and square to the table by using two small magnets. The aluminum square at the top of the photo is used to align the top edges of the 3 parts. Running through the two side pieces is a 3/8″ center punch, just to make sure I aligned the holes.
After welding it together, here’s what I ended up with. Not bad.
I’m not sure you can tell in the photo, but here is mistake #2. The holes that allow this part to be bolted to the frame, are off by about and 1/8 of an inch. I’ll have to check how the cab bolts to this part to see if there is enough play or if I’ll have to remake this part.
This is the first project I started after getting my steel shipment. In the first photo you’ll see how I drew this out as 5 separate pieces. Reason being, this piece bolts to the frame rail using 6 bolts and they must align along the frame rail length as well as along the top edge of the frame rail.
You can see in the photo how the original piece is bent into a c-channel shape along it’s length, and then bent perpendicular to establish the tabs that were originally riveted to the frame. What I was up against was that I had to make sure that when I bent this up, that the holes had the correct width spacing as well as vertical spacing. I found a formula online about how to calculate what’s called “bend allowance”, but I wasn’t sure I could get this absolutely right, so I made it up into 5 pieces that would be welded together.
First step was to weld the c-channel shape by welding the side pieces to the top:
Even after all my careful measurements, I still made a mistake. Here’s one of the tabs which allow the body mount to be bolted to the frame rail. I’m not sure where I messed up but you can see I was way off. I’ll have to make this part from hand and not used the laser cut parts.
Here I’ve bolted part of the body mount to the original frame rail. The next steps are to bolt the two tab pieces to the frame rail and then tack weld the tabs to the body mount side pieces. This will ensure that the part will bolt back up to the frame rail. Assuming I have the measurements right on the laser cut pieces. As I write this I think I’ll wait to bolt it up to my manufactured part instead of trying to bolt it to the original. Once I’ve tacked it together on my new frame rail I can double check it against the original to see how far off I was.
It’s been a while since I posted but I wanted to catch everyone up to where I’m at in the build process.
When I started off writing this post I was going to go into detail about what’s happened over the last 6 months or so, but this just became too much work.
Suffice to say I’m starting over.
What happened was that I cut built my own frame by cutting pieces out of 1/8″ steel plate using my plasma cutter. Thing were going along well until I put too much heat into the welds and ended up warping the frame rails. I thought I could straighten them out with some heat from the oxy torch but not to my satisfaction, or more likely, I don’t have the necessary skills to do this.
So I’ve decided to start over, but this time I’m going to put a little more thought into it.
Over the last few months I’ve been corresponding with a fellow car nut from Ireland who is also interested in building a ’56 Ford F-100. Problem is, he doesn’t have access to an original frame. Ian turned me on to a builder Paul Horton ( www.welderseries.com ) who has an interesting way of making parts for your hotrod.
These little tabs on each piece help locate the parts relative to each other. Kind of like the paper models I used to put together where you put Tab A into Slot B.
Taking inspiration from this approach I set about making some CAD drawing of the ’56 F100 frame I do have. I started off tracing the outline of the frame onto a sheet of 1/4″ 4′ x 8′ plywood. Since the frame is almost 16′ long I had to trace it as a front and rear section. From this outline I could start taking dimensions to holes that I needed to keep. I’d center punch the hole into the plywood and then take measurements from this indentation. What was really a challenge was all the curves on the frame. I really struggled with this until I remember some high school geometry around tangents and circle radius being perpendicular to the circumference. What I did marked every frame transition from a flat part into a curved part. At this transition, I would draw a perpendicular line or ray. When the curve stopped, I would draw another perpendicular line or ray. Where these two lines met, that would be the centerpoint of the arc. I could then measure this distance and the angle to know how to draw this arc in the TurboCAD.
Here you can see what the plywood ended up looking like when I was through (it’s hard to read all that’s there):
From this tracing I started transfering the dimensions into TurboCAD. After spending several weeks doing it over and over again I came out with something that I felt was close enough to what I needed. And after checking with a local steel company (www.discountsteel.com) around how much it would cost to have this cut out, I sent the plans off.
Today I picked up the parts and boy does this look fantastic. Here are some pictures showing how the front and rear sections will go tother as well as a few pictures for other brackets that are used on the frame.
For some reason the rear section messed up. I ended up with two inside parts instead of an inside/outside part. I checked the drawing I sent and both pieces are there. I’m not sure how this happened. I’ll have to check with the DiscountSteel to see if they had to make any modifications to my drawing.
Here you can see how the front and rear sections will be joined together. I’d be hard pressed to be able to produce this accurate of a cut using the plasma cutter by hand.
The main body mount to the frame. I’ll go into details on why I made this as 5 pieces instead of one in a future post.