So, I am on my way to adopting this new great idea. I have made myself a new pair of blocks to use in the trimming sandwich to the new design of the tabs. I cut the bottom off of the previous blocks to eliminate the tooling hole in the bottom corner mainly so that I can eliminate it also in the several blanks I have both tooling holes drilled in. I'll use one of these new mounting holes for tooling and making the sandwiches.

As to the captured nuts on the tabs I don't think I'll use rivnuts but rather a nut plate from my aviation background that gets riveted to the back of the tab. I put one in the pictures below. The one shown is not exactly the one I'll be using, but you get the idea, and I'll have to order a bunch of the correct ones for this project. In any case I'll still get to do some riveting for this project after all.

 

'Cuz the distance from start to prototype is similar to the distance from prototype to production.

Getting the pan to form is great.

Figuring out how to make them efficiently is "a whole 'nuther" deal.

I really like the idea of making them 'height adjustable'.
Not something I would have thought of, but I didn't have a pan on mine until well after I put new MMs in.

 

Thanks, Joe. The distance from start to prototype in this case is right at a year. I started this project in the other thread last December and started this thread on Jan one this year. From here to production is going to be a bit of time, but not another year, I am certain. In fact, I hope to have the first one of these production models in the mail by this next Jan one.

The "adjustable" concept for the tabs came to me on this Forum and is close to genius, particularly given what I think is my revelation about the relation to the motor mounts issue. Too, I have just figured out how best to make the slots in the pan for the adjustment. I am going to make a simple drill jig for the start holes, but rather than have just one hole to elongate with the chain saw file for each slot I realized that I can drill two holes, one at each end of the slot and then simply connect them with the file. I can do all the riveting on the tabs here in the house so that in the production process all I will have to do is select the pair of tabs and loosely bolt them to the pan. I have started working up the remainder of the tab blanks (about a hundred pair) into the new tab design and I am going to try to locate and order the nut plates and bolts for the adjustment aspect.

 

Side cutting straight mill?

 

And, I still pretty much don't want to think about it.

But, when I went to bed last night I was thinking about how much time it was going to take to connect the two holes in each slot with the chain saw file, and how accurate that was going to be. Then when i woke up this morning I had a pretty clear image in my mind of a plywood jig bolted to the mill table with a fence on it and various relief slots cut in it for the flanged edges of the ends of the pan and two hinged hold down kind of bars with captured bolts and wing nuts on them to clamp the pan down so I could locate the mill bit in a hole and elongate it for the slot.

Now I think that even if I only set up and do one pan at a time it might be easier and quicker and better looking to use the mill as you suggested, Martin. For two or three or a few pans in a group it will save a bunch of time.

OOPS, I clicked on edit rather than quote and ended up deleting much of the previous post about why I was going to use the file and not the mill. DUH!

 

I bumped this thread because the just above post ended up edited rather than the intended new post with one line quoted from my previous post just above it.

 

I continue to work on this last version of the top mounting tabs. I ordered some flange nuts to rivet onto them and they have not come yet. I'm going to mark and bend one or two of them to see just how close I have guesstimated for the hole or slot location for the top of them. The problem is that when the tab moves up and down to match the desired location of the trailing edge of the pan they also move inward and outward some by virtue of the 32 degree slope of the end panels of the pan. What I need to end up with is the distance between the tabs at their lowest position at about 35 and 5/16 inches between centers and at their most likely upward position about 35 1/2 inches. The pans are pretty stiff, but I think they are flexible enough to work in that range.

 

The flange nuts came. In the catalog they are called "Anchor Plate Nuts." The picture shows how they will be oriented on the tabs. They will be riveted with 3/32 inch aircraft rivets that are counter sunk on the back side so that side will be flush against the side of the pan. I have marked a few and the two that I have bent to my mark show that they are just about perfect for placement.

I still have a lot of these to work up before I get into production and that takes a lot of time. All the holes and edges of the tabs have to be deburred and that is tedious work. Then the hole at the top still needs to be elongated into a slot. I did cut the last piece of material into tab blanks yesterday and will continue to drill the holes then start again to mill them into shape. In the meantime I hope to form a couple of pans this weekend and expect that they will become the first production versions of these pans. The final touch will be to paint them.

The one in the picture that is cut off at the top is my marking guide for bending.

 

David K, who recently located here in GJT with his wife and their 928. came over yesterday for a kind of introduction and orientation to some of my projects, including this belly pan effort. I was finishing up some tab blanks in the mill and disc sander and then we went over to the other shop and worked up a sheet of material and pressed another pan. This one cam out servicable, but is still a prototype because it formed with the warp in it. I think I have figured out now why it will do that. I'm going to press another one today to make sure I have it right.

I obtained some longer screws for the forming blocks for the top tabs so I can now sandwich 14 or 15 together to mill and sand to shape. That saves some time, but I still have about 70 or 80 blanks to mill to shape, and even then that is only going to give me enough tabs for about 50 or 60 pans. Since the nut plates have to be riveted to these tabs and those must be counter sunk to be flush on the back I have ordered some tools to accurately do that with. A regular countersink will not work for these rivets since aircraft rivets are counter sunk at 100 degrees rather than the common 90 degrees. Too, I need to be able to accurately sink them, so I have ordered a micro stop devise to help with that.

Then I will have to drill all the blanks for the four rivets and that will take putting them in a sandwich again, but only with about 5 or 6 at a time. The rivets are 3/32 inch but they will not quite fit in a 3/32 inch hole so the hole must be drilled with a number 40 bit which is 5 or 6 thousandths larger. Then I have ordered a rivet squeezer to set the rivets with since I don't want to be trying to set them with a hammer or even an air hammer. My existing river squeezer is just too big for this job since the tabs are so small and I have only two hands. Clamping my big squeezer in a vise might help, but I thought a much smaller one, especially for these tiny rivets, will be much more handy.

 

I don't know if it would serve your purpose, but one of my favorite tools is an inexpensive HF air-over-hydraulic riveter. My grip ain't what it used to be and I've had some jobs, like riveting new liners in a horse trailer, that I just couldn't do without this thing.

 

Martin, I'm going out to HF right now to get some sanding discs since I have had to stop and work my belt/disc sander over in order to make some progress. I'll have a look at their riveter, but I have a hunch that what you are talking about is a pop rivet tool. Pop rivets are really at the bottom of the list in terms of usefulness for me. Next up are soft hardware rivets, and those would probably do fine for this project, but at the top are aviation hard rivets, and those are what I am most used to using and they provide the most strength. I don't need a lot of strength, here, but I'm still going to use them since setting them is not much more trouble, if any, than soft rivets. As to pop rivets, I doubt that I could find any in 3/32 inch diameter, and that are countersunk, and at 100 degrees.

I don't really have anything against pop rivets and I even covered a small trailer one time using them, but still . . . .

 

I have that and use with steel rivets. Love it.

 

Show a picture of it and tell whet kind of rivets it pulls. I was at HF and completely forgot to look at one if the had one.

 

It pulls a different size rivets. Swappable heads.

 

There's a big difference between a rivet puller and a rivet squeezer. A rivet puller sets pop rivets which are basically hollow, and a rivet squeezer compresses solid rivets into their final form. I am going to use the rivet squeezer and will not be relying on pop rivets in this project.