After rallycross season ended I noticed a few scrapes on the Subaru’s oil pan. Nothing terrible, but enough to cause me a little worry. With The Trail of the Gnu rally coming up soon I thought it might be prudent to get some protection under there.
I was originally intending to do a plastic skid plate made out of ¼" HDPE plastic. It’s lightweight, slides well, and is relatively strong. It can also be cheap, depending one where you buy it. The supplier I visited in Calgary quoted me about $75 for a 3 by 3 foot piece, and I thought I could do better.
Off I went to the only metal scrapyard in town that still sells to the general public, and I came back with two chunks of square aluminum tubing and this gigantic decommissioned road sign, all for $10.
To start, I took some general measurements and made my first cut. For this project I experimented with using wood tools to cut and shape the aluminum, and it actually worked really well. Well enough that I will continue doing so for future aluminum projects. You’ve just got to go nice and slow! That, and get rid of any cloth sawdust collector bags or they will burn.
Here’s an alternative to a table saw - just clamp a good edge to the workpiece and use that as a guide for the circular saw.
A nice straight cut!
With the car up on ramps, I used my floor jack to support the freshly cut aluminum and made some alignment marks:
I marked the curved profile of the bumper on the sheet, then straightened that line into three sections. These would be bent up to protect the leading edge of the car, kind of a chin protector. The excess metal on the corners was cut off.
Now came the hard part: bending the front. I really just need to invest in a metal brake for bending aluminum - this was pretty ridiculous. My first attempt involved some plastic clamps and some chunks of wood, with a piece of threaded rod to provide a radius to curve around.
All this ended up doing was breaking my plastic clamps! Revision 2 involved my vise and a long piece of 2x4 screwed to it.
This was more successful, but still took a LOT of effort to get the bend! I took it up to about a 45 degree angle.
Here is the result, along with a small strip of cut aluminum that would be added to the front to reinforce the curve.
Okay, that’s the basic shape of the plate taken care of, now to see about mounting it to the car and reinforcing it. I decided to make an aluminum frame to support the sheet. With a proper bending brake, you could potentially reinforce the sheet just by adding structural ridges, but being that I don’t have one I would have to add some tubes to give it the needed rigidity.
I started with some simple 1x1 square aluminum tube. This would attach to the front of the jacking plate - a sturdy location just behind the oil pan.
Also note that the bolts that hold the jacking plate to the frame are held on by two free, unattached nuts - necessitating both a socket and a wrench to hold the nut still. With the skidplate in place, there would be no access to the nuts. I decided to add a quick tack weld to the nuts to keep them from spinning. Access was tight for the welder, but the result works well and now they can be removed with only a socket.
With the back of the frame in place, I used a straightedge to see how much clearance there was between the oil pan and the skidplate. I found out that to keep an adequate gap, my front attachment point would need to be lowered by about 1 inch. Unfortunately I was out of 1 inch aluminum tube, which necessitated a quick trip to Home Depot to pay an outrageous price for their metal. As an unapologetic cheapskate I found this to be highly degrading.
The new piece was drilled in order to be attached to the radiator support. There were two threaded holes already in the support (for the rare factory Subaru skid plate), but they were loaded with rust due to being very exposed to the elements with no bolts to close them up. A tap was used to chase the threads, then my new Home Depot front frame piece was installed.
I now had a front and a back to which I could attach the plate. I wanted lots of support, so some sides were in order. The sides would also give more strength to the rear of the bar, for they would end up right over the front sway bar mounts - a sturdy spot for a skid plate attachment point.
For the sides, I cut some 1.5-in square aluminum tube into right angle pieces, with an elevated section to meet up with the sway bar mounts.
The double-stacked tube isn’t my most graceful fabrication, but it works. I really wish I could weld aluminum - that would have been much neater.
Another angle on the side piece:
With the side pieces in place, I was still not happy with the support of the big floppy plate, so two more cross braces were installed around the oil pan.
I made sure to mark the braces with an approximate location for the drain plug and oil filter - this would make cutting out access holes sliiightly more accurate later on. I also made sure everything was nicely squared up.
It was then time to attach the plate to the frame, albeit temporarily. Four rivets held the plate in place.
….rivets which were promptly drilled out and removed. They only served to hold the plate in place and keep it aligned for later assembly (clecos, a special kind of temporary rivet, would have been great for this). The plate would need to be removed to allow access to the frame mounting bolts.
Everything comes off…
…and is then reassembled off the car, so access holes for the mounting bolts can be drilled into the plate.
One more install of the plate and frame onto the car ensured that it fit correctly. The more layup and assembly that can be done actually ON the car, the better it will fit. However, there was no way I would be riveting everything together while lying on my back under the car.
Out it came again so that I could go crazy with rivets (and be visited by a friendly bunny):
Rivets aren’t ideal for this as the plate should be completely flat - but since I can’t weld aluminum it would have to do.
Almost done now! I jigsawed access holes for the oil plug and filter, and added some ventilation holes (or “speed holes”) to encourage airflow past the radiator and intercooler.
And then, final install!
I’m fairly pleased with it. Altogether it only weighs about ten pounds or so, and should give my engine and bumper some additional protection. Theoretically, it should even give a slight increase in fuel economy due to the better airflow over the flat surface.
Ready to murder some cones:
Cost breakdown:
$10 - scrap sign and square tubes
$18 - 36" aluminum square tube from Home Despot
$5 - rivets
==$34
I was originally intending to do a plastic skid plate made out of ¼" HDPE plastic. It’s lightweight, slides well, and is relatively strong. It can also be cheap, depending one where you buy it. The supplier I visited in Calgary quoted me about $75 for a 3 by 3 foot piece, and I thought I could do better.
Off I went to the only metal scrapyard in town that still sells to the general public, and I came back with two chunks of square aluminum tubing and this gigantic decommissioned road sign, all for $10.
To start, I took some general measurements and made my first cut. For this project I experimented with using wood tools to cut and shape the aluminum, and it actually worked really well. Well enough that I will continue doing so for future aluminum projects. You’ve just got to go nice and slow! That, and get rid of any cloth sawdust collector bags or they will burn.
Here’s an alternative to a table saw - just clamp a good edge to the workpiece and use that as a guide for the circular saw.
A nice straight cut!
With the car up on ramps, I used my floor jack to support the freshly cut aluminum and made some alignment marks:
I marked the curved profile of the bumper on the sheet, then straightened that line into three sections. These would be bent up to protect the leading edge of the car, kind of a chin protector. The excess metal on the corners was cut off.
Now came the hard part: bending the front. I really just need to invest in a metal brake for bending aluminum - this was pretty ridiculous. My first attempt involved some plastic clamps and some chunks of wood, with a piece of threaded rod to provide a radius to curve around.
All this ended up doing was breaking my plastic clamps! Revision 2 involved my vise and a long piece of 2x4 screwed to it.
This was more successful, but still took a LOT of effort to get the bend! I took it up to about a 45 degree angle.
Here is the result, along with a small strip of cut aluminum that would be added to the front to reinforce the curve.
Okay, that’s the basic shape of the plate taken care of, now to see about mounting it to the car and reinforcing it. I decided to make an aluminum frame to support the sheet. With a proper bending brake, you could potentially reinforce the sheet just by adding structural ridges, but being that I don’t have one I would have to add some tubes to give it the needed rigidity.
I started with some simple 1x1 square aluminum tube. This would attach to the front of the jacking plate - a sturdy location just behind the oil pan.
Also note that the bolts that hold the jacking plate to the frame are held on by two free, unattached nuts - necessitating both a socket and a wrench to hold the nut still. With the skidplate in place, there would be no access to the nuts. I decided to add a quick tack weld to the nuts to keep them from spinning. Access was tight for the welder, but the result works well and now they can be removed with only a socket.
With the back of the frame in place, I used a straightedge to see how much clearance there was between the oil pan and the skidplate. I found out that to keep an adequate gap, my front attachment point would need to be lowered by about 1 inch. Unfortunately I was out of 1 inch aluminum tube, which necessitated a quick trip to Home Depot to pay an outrageous price for their metal. As an unapologetic cheapskate I found this to be highly degrading.
The new piece was drilled in order to be attached to the radiator support. There were two threaded holes already in the support (for the rare factory Subaru skid plate), but they were loaded with rust due to being very exposed to the elements with no bolts to close them up. A tap was used to chase the threads, then my new Home Depot front frame piece was installed.
I now had a front and a back to which I could attach the plate. I wanted lots of support, so some sides were in order. The sides would also give more strength to the rear of the bar, for they would end up right over the front sway bar mounts - a sturdy spot for a skid plate attachment point.
For the sides, I cut some 1.5-in square aluminum tube into right angle pieces, with an elevated section to meet up with the sway bar mounts.
The double-stacked tube isn’t my most graceful fabrication, but it works. I really wish I could weld aluminum - that would have been much neater.
Another angle on the side piece:
With the side pieces in place, I was still not happy with the support of the big floppy plate, so two more cross braces were installed around the oil pan.
I made sure to mark the braces with an approximate location for the drain plug and oil filter - this would make cutting out access holes sliiightly more accurate later on. I also made sure everything was nicely squared up.
It was then time to attach the plate to the frame, albeit temporarily. Four rivets held the plate in place.
….rivets which were promptly drilled out and removed. They only served to hold the plate in place and keep it aligned for later assembly (clecos, a special kind of temporary rivet, would have been great for this). The plate would need to be removed to allow access to the frame mounting bolts.
Everything comes off…
…and is then reassembled off the car, so access holes for the mounting bolts can be drilled into the plate.
One more install of the plate and frame onto the car ensured that it fit correctly. The more layup and assembly that can be done actually ON the car, the better it will fit. However, there was no way I would be riveting everything together while lying on my back under the car.
Out it came again so that I could go crazy with rivets (and be visited by a friendly bunny):
Rivets aren’t ideal for this as the plate should be completely flat - but since I can’t weld aluminum it would have to do.
Almost done now! I jigsawed access holes for the oil plug and filter, and added some ventilation holes (or “speed holes”) to encourage airflow past the radiator and intercooler.
And then, final install!
I’m fairly pleased with it. Altogether it only weighs about ten pounds or so, and should give my engine and bumper some additional protection. Theoretically, it should even give a slight increase in fuel economy due to the better airflow over the flat surface.
Ready to murder some cones:
Cost breakdown:
$10 - scrap sign and square tubes
$18 - 36" aluminum square tube from Home Despot
$5 - rivets
==$34
No comments:
Post a Comment