Wednesday, March 17, 2021

Big post today!

Today, I continued working on the mounting "toes" for the firewall. First, I used my 3D printer to make some spacer blocks. This let me provide a consistent offset between the face of the fuel tank and the firewall.
Here they are on the floor of the car, just aft of where the driver's seat will go.
And here they are looking down between the firewall and the tank. This let me get the angle brackets I had made all drilled and riveted up, so the lower portion of the firewall is all ready to bolt into the car.
To get the upper part ready, however, I will need to change tactics. Here are two rivets - on the right is the "pop" type that I have been using for most of the panel attachments throughout the car. The disadvantage of this type of rivet is that it is not flush on either side of the joint; on one end, it leaves a small domed surface, and on the other end, it leaves a protrusion which is even larger.

On the left is a bucked style of rivet, which is set with a rivet squeezer; it actually deforms into countersunk a countersunk hole on the back of the work to provide a flush finish on both sides.

These are aircraft rivets, used in applications where drag reduction is paramount, so no protrusions can be allowed.

Here's my first experiment is using these bucked rivets. This is the back side of a joint I made in a couple of pieces of scrap. I took two pieces of 1/8" aluminum, drilled holes and made countersinks on both sides, and used a rivet gun to deform the "shop end" of the rivet to fill the countersink.

Safe to say these pieces are securely fastened. I did a few more just to do it, and they all worked very well. I'm convinced.

Last but not least, here's the upper section of the firewall. It's all Clecoed up to a piece of angle, ready for the rivets to go in. I haven't shown it, but the holes are already countersunk on both sides, and I just have to buck the rivets.

That's for next weekend, though.

Tuesday, March 16, 2021

An overdue update

I haven't been good about updating in the last couple of weeks. I don't feel like I've had a lot of time to work on the care lately, given other obligations - but here's what I have been up to.

Here's the fuel tank in the car. It sits back flush to the vertical place formed by some frame members. It's a bit hard to see from this picture, but there are a couple of things that protrude through  that plane, and therefore through the firewall skin I am putting there - the filler neck and the vent fitting.

So, with the firewall skin mounted in the car, I marked and cut the holes for those items. The vent hole will probably need to be enlarged later, but the filler hole is just about perfect. 

Tubes from both of these will go up and outboard (left in this picture) to the fuel filler on the fender.

Here's a detail shot of that same location from inside the car.
Because I am not using the supplied fuel tank from the kit, I also have been working on building a firewall to replace the kit firewall between the fuel tank and the passenger area.

Here, I have three panels mocked up to form the lower and middle sections. There's also going to be a vertical upper section lying tight against the upper aft firewall skin (this gets important later), and a small lower center section to cover most of the gap (but leaving a space for shift cables and wiring to pass through).

And here, I am working on the "toes" of the firewall, which will be bolted to the floor of the car. The tank itself also has mounting toes as well as some tabs at the top which will be bolted to / through the frame, so the tank is really going nowhere.

Tuesday, March 2, 2021

Firewall and fuel tank progress

Using one of those "stretched" angles I made last time, I started building a firewall to go forward of the fuel tank. Here, I have the angle attached with Clecos to a piece of sheet aluminum. There's a gap in the hole pattern because I need to cut out a window in the middle. This will form a passthrough for shift cables, wiring, and so on.
Here it is in the chassis, with the window cut out. This is going to be partly covered by a panel across the bottom, attached with screws so I can remove the firewall later to service the tank, should I need to.
I also did a little work on the fuel level sender that came with the tank. The sender is a 0-90 ohm unit - but the Subaru fuel gauge expects a 90-0 ohm input. So to avoid a reverse reading in the dash, I had to reverse the throw on the arm. And, because the sender unit is at one end of the tank, I then had to reverse the position of the actual potentiometer on the mount, so the float would still be to the right.
This is the reason I could not just rotate the sender 180 degrees - the mounting flange has an odd number of screws holding it down. I did try it at a 144 degree (two holes) rotation, but the arm fouled against the wall of the tank.

Next up is to get the tank actually bolted to the chassis. It does have mounting ears (you can see one of them in the previous picture), so I will drill through those and get some bolts into the frame and the floor. I am waiting on some rubber tape, though. Should show up today.