If you have problems with the nuts being on an angle, you can make your own washers from the top and bottom flange of your c-channel. It naturally has the proper slope. If you decide to do this, I would drill the holes first, then run the flange thru the table saw, then finally use the chopsaw (mitersaw) to cut into squares.
One of the reasons I don't like the idea of not using them is that you will be introducing a bending moment into the bolt. I'm not sure how critical that would be...
Thank you, another good point, which is why I love discussing my harebrained schemes in an open forum.
My (mild) concern was that the nuts would not be grabbing evenly across the threads, which might lead to stripping the nut off. I did not think about the bending action on the bolts. If the self tappers were a decent rate of steel, I would still have no worries.
As I dozed off last night, I had a come to Jesus meeting with myself. I’m disappointed in my self tapping bolts, but they are working for doing a quick layout. But the more I fool with them, I don’t trust them at all under a load. I love building crazy stuff, but I don’t have a death wish.
Speaking of the load, it’s not just the trailer and taking corners and hitting bumps, it’s a dynamic loading a little bit like a tanker. If I have a compartment or two full of beer or soda and ice, and maybe the ice is partially melted, it can slosh around from side to side and forward the back. I know from working with Heil tankers years ago when I worked in the chemical plant, that such motion of liquids can create tremendous spot loading in just about every direction, and, of course, at the perfectly wrong time.
So with y’all’s comments, and my Epiphany, before I go any further, I’m going to upgrade all the bolts and change my methods. I was always planning on drilling out certain spots and putting in the 1/2” stainless bolts I acquired. On the rest of the holes, I’m going to upgrade to 3/8 inch steel bolts. I don’t know the grade rating is on the self tapping bolts, but they sure aren’t grade 8!
On 90% of the self tappers, I am going to reverse the direction of the bolt so I can tap the current feed side to the receiving side with a 3/8-16 thread. And whether I use some more of the self tapping or the 3/8, or something else, I’m going to tap the holes with the tap, and not rely on the self tapping bolts for anything halfway critical. It’ll take a little longer, but it’s still not a big burden since I can use my five dollar Ryobi pawnshop reversible drill to do the tapping if I use a little WD-40 with it. It goes quick.
The other catalyst to this decision was thinking out my spring hangers. They’re definitely going to be steel, but I’ve been doing a lot of thinking on how to attach them to the aluminum.
I think I’m going to fab them with a leg that rises on the inside side, so I do the usual two bolts through the bottom of the channel, but then I can also put one or two bolts through the web on the riser. Something like that, it’s still in development.
I went through all my inventory, and I didn’t have any steel pieces that I could convert easily, so it killed me, but I went down to Metal Supermarket and bought a drop 2 in.² tube, 48 inches long for $22 that I could chop up and make the spring hangers. I’ll have enough for this and the next project.
The final thing that spurred me to fixing the bolts in the frame now was thinking about how the gas grill will be mounted. I think I figured that out, but the bore things I do to the frame, the harder it will be to square it up later.
So I’m going to upgrade the bolting, make, and mount the spring hangers, and about the axles after adjusting them to the right length. A couple steps backwards, but it will be a much better result. This is also the guinea pig for the converter dolly, and I’ve been learning tons.
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