Anybody lowered a convertible seat pan?

[Shaun]

My new seat is low, but not as low as I'd like. I hacked a bunch out of my coupe pans and loved how low I sat. I'd like to lower the convertible pan I'm installing. Anyone done it? How did you do it? I know I'll have a fair bit of fab work to do so just looking for ideas...

Here is the seat. Its a Ultrashield Full Containment Road Race VS Halo. Oh yeah, the 2x4 being used as a back brace will be replaced!

[Dennis Harrelson]

Section the seat pans front & rear, leaving the bottoms and the hump intact, then extend the hump down to meet....?

[Shaun]

Section the seat pans front & rear, leaving the bottoms and the hump intact, then extend the hump down to meet....?

Yeah, thats what I was thinking.  Just seeing if anyone had done it and knew of any shortcuts...  Trying to keep this project from creeping as I need the car back working in a few months.

[Dennis Harrelson]

Thanks for the picture anyway. I've been thinking of trying to fab a hump reinforcement and it's nice to see how the convertible fits.

[ZFORCE]

I have been looking forward to this job for a long time, to fit my 95GT seats in my 67 vert.  Here is what I'm planning on doing.  This is like that school assignment where you have to write down instructions on how to tie your shoe, so bear with me!

1) Scribe a square, the largest flat area around the mounting holes as you can (it should take you to the vertical metal in front and at the rear of the seat pan),

2) then cut that section out.

This will leave the vertical seat pan metal in front and in the rear of the seat pan. as well as the vertical metal coming down from the transmission hump, and the vertical metal coming down the seat pan along the rocker panel.

3) cut and remove the vertical metal in the front and back of the seat pan.  You will now only have the small horizontal strip of metal that is spot welded to the floor pan left.

4) You will then lay your seat pan "square" that you cut out in step 2 (the one the seat bolts to.) back where you took it out.

5) Take the two vertical pieces you cut out of the seat pan from step 3).  You will then use the metal as filler metal to add to the hump and the rocker metal to extend them downward meeting the seat pan again.

6) Stitch weld it all together and you're done!
Well, I hope that is clear!

[stangg]

I only lowered the front on mine to compensate for the steep angle of the fox seat bottom to keep my knees off the steering wheel.    If I remember right, I sliced across the front of the pan about 1" down from the top.  then ran a slice on either side, just where it begins to curve up.   With the front pushed down, hammered the remaining front vertical lip back to meet the top corner and welded it.  For the sides used some 1/8" stock to fill the traingular shaped gap front to back.

I didn't really want to lower the rear since it is so short already and I didn't want to lose the strength that the vertical portions of the base provide.  I really didn't want to compromise something that I added for strength reasons...

[Shaun]

I really didn't want to compromise something that I added for strength reasons...

Yeah, that is what I'm struggling with.  I can lower it sure, but it'll loose some of its strength if I just cut out the top and lower it.

My fixed back seat has a 20 degree layback so I may explore what you did to see if by doing it I'm not sat too upright.

I'll have to put the seat back in and see what else can be done.  I'd rather not mess with a tilt column but I really dislike the stock seating height so something will have to be done.

[Dennis Harrelson]

Aren't they the same height as the coupes and fastbacks? I took 1 1/4"+/- out of the front and back both and it still left an inch or so vertical in the back. Way more complicated, but probably could be done.
edit: and I just lapped the section, so it doubled the vertical walls.

[Shaun]

Aren't they the same height as the coupes and fastbacks? I took 1 1/4"+/- out of the front and back both and it still left an inch or so vertical in the back. Way more complicated, but probably could be done.
edit: and I just lapped the section, so it doubled the vertical walls.

I haven't measured but I'm sure they are the same.  The issue is that the entire point of putting the convertible seat pan in is to build beam strength from one rocker, over the trans. hump to the other rocker.  By lowering the pan and shortening the vertical front/back piece I'm reducing the beam strength unless it gets reinforced somehow.

The weekend is coming, I'll figure something out.

[AzPete]

Can you compensate with support under the floor pan?

[Dennis Harrelson]

I haven't measured but I'm sure they are the same.  The issue is that the entire point of putting the convertible seat pan in is to build beam strength from one rocker, over the trans. hump to the other rocker.  By lowering the pan and shortening the vertical front/back piece I'm reducing the beam strength unless it gets reinforced somehow.

The weekend is coming, I'll figure something out.

Like I said, lap it & it'll be double. You'll still have to extend the hump piece down, but I don't thinkshortining the front & back will affect strength that much, as long as you leave some vertical to create a box. If you're real worried, add a truss member in the middle of the pan running lt--> rt, welded to the floor & pan and it should compensate for any loss.
Hmmm....maybe.

[Shaun]

Today I pulled one of my street seats out of the attic and put it in the car. There is no way I want to sit like that! Even if modifying the pan reduces the stifness it gives the chassis, my seating position takes precedence. I have the TCP X-brace and whenever the car has slicks it'll have a roll bar installed so I already have some good lateral support.

I wanted to cut further up the trans. hump and attempt to re-create the contours with the patch. After an hour looking at it I decided it would be way to much work for something that won't be seen when the seat is in. I'm not Jesse James and I don't have an English wheel (nor a Nazi fiancee freak either).

So straight sides it will be:



Once cut out I had to flatten the pan out and make a new bend further out because it needs to be wider when mounted lower down:





I trimmed the downward pointing flange and fit/welded it to the base:



Took out 1.5":



I then made pieces like this for the sides and plug welded them in from the backside and filled/ground the front:





Phew, it still fits in the car...



Now that I've hacked out most of the structure that gives this piece strength, and is the reason why I did the convertible pan, I now have to figure out a way to add some strength back. I'll probably build/weld a framework to the underside before it goes into the car for good.

[stangg]

That looks great!!!   So are you not putting the lower pans in due to the TCP X brace?   If not,  is there any clearance between the brace and the floor?  On the top pans,  I think some gussetts laid at an angle at the corners after installation would be about all you need to beef the corners back up.   
   

[LastDeadLast]

Looks awesome Shaun.  Take good pics of the reinforcements that you do with the underside of the pan.  I might do this to my vert one day.

-Shannon

[Shaun]

That looks great!!!   So are you not putting the lower pans in due to the TCP X brace?   If not,  is there any clearance between the brace and the floor?  On the top pans,  I think some gussetts laid at an angle at the corners after installation would be about all you need to beef the corners back up.   
 

Not planning on using the convertible lower pans.  Probably not any room with the 'X' brace.

Almost have the drivers side lowered and finished up but have to take a break and get some real work done!  I'll think about if and what sort of bracing to add this week...

[Shaun]

Finished up lowering the drivers side.  The new seat sits really fricken low, like a DTM driver.  I LOVE it!

Still got to decide if and what bracing I'll put underneath before installing it into the car...

[ZFORCE]

So Shaun, after you welded everything up, did it feel more flimsy?  I'm just wondering why you think it lost so much strength, it has all the metal and boxing it previously had??

[Sluggo]

So Shaun, after you welded everything up, did it feel more flimsy?  I'm just wondering why you think it lost so much strength, it has all the metal and boxing it previously had??

Agreed. I would think the end plates you added in only added rigidity.

[stangg]

The main point of the 1 piece seat pan is to strengthen the unibody between the rockers.   The vertical portions of the riser is where the majority of that load is transferred across.   What used to be about an inch and a half of vertical wall at the base of the trans tunnel is now cut down to about a 1/2 -3/4" (guessing on the actual measurenment)  but that where the loss is...   I'm pretty sure adding some flat stock diagonally from the vertical to the edge of the flange will beef that section up by essentially boxing that corner.   IMO,  that's where the weekness is... how severe probably not much,  but theoretically narrow paths, with sharp cornes isn't necessarily  a good thing...

[Shaun]

The main point of the 1 piece seat pan is to strengthen the unibody between the rockers.   The vertical portions of the riser is where the majority of that load is transferred across.   What used to be about an inch and a half of vertical wall at the base of the trans tunnel is now cut down to about a 1/2 -3/4" (guessing on the actual measurenment)  but that where the loss is...   I'm pretty sure adding some flat stock diagonally from the vertical to the edge of the flange will beef that section up by essentially boxing that corner.   IMO,  that's where the weekness is... how severe probably not much,  but theoretically narrow paths, with sharp cornes isn't necessarily  a good thing...

Thanks guys.  I'm going to take another look at it this weekend and see what I can do.  I do have the TCP x-brace under the car which is providing some good strength and I'll run with a roll bar w/diagonal bar on the track so I'm not too bothered that the seat pan needs to supply a massive amount of additional bracing to the floor.  After spending $150 on the pan and materials and an entire weekend cutting and welding lowering the damn thing, I got a sinking feeling wondering what was the point!?  If I've hacked out any strength it provided then I should of just saved the cash/time and modified the stock coupe ones that were already at the height I liked them!  Bugger!

[Shaun]

So I bit the bullet and just welded the sucker in.  It isn't as stiff as it was originally, but its stiffer than the coupe pans.  Along with the X-brace underneath and the roll bar I think the torsional strength of the floor should be quite good. I wish I had taken the time to rig something up to actually measure the improvements but oh well.

I welded in some 1/8" thick, 2" x 2" plates under the seat mounting holes to hopefully prevent tear out if ever the car is in a shunt:


Painted the underside, painted the floor underneath and welded it in:






Another side project, filling the 4 floor drain holes for a cleaner look.  Flattened the lip with a hammer and dolly, cut a patch, welded in and smoothed:
 







Does it ever end?  At some point I need to stop messing around and get painting and put this back together!

[stangg]

Very nice workmanship Shaun...    it looks like you have it very well covered with everything you've got going on there. 

[LastDeadLast]

Shaun,

Great work!  It looks awesome!

Not to hijack your thread, but I have a question that is somewhat related to your project. 

I'm wanting to replace the under-dash parking brake with a hand brake mounted on the trans tunnel.

The big knock is that I've got a convertible with the reinforced seat pan and the optimal mounting position for the hand brake is smack dab in the middle of the reinforced ridges.  Any ideas on how to do this so that I don't loose any strength?

Any ideas would be appreciated,
-Shannon

[Shaun]

Shaun,

Great work!  It looks awesome!

Not to hijack your thread, but I have a question that is somewhat related to your project. 

I'm wanting to replace the under-dash parking brake with a hand brake mounted on the trans tunnel.

The big knock is that I've got a convertible with the reinforced seat pan and the optimal mounting position for the hand brake is smack dab in the middle of the reinforced ridges.  Any ideas on how to do this so that I don't loose any strength?

Any ideas would be appreciated,
-Shannon

I've never seen how the trans. tunnel mounted handles work...  Couldn't you box in the ridges and mount it up there?  Or, just stick with the under dash one.  You got short arms?  Or are you planning on running some rally stages?   

[Shaun]

Very nice workmanship Shaun...    it looks like you have it very well covered with everything you've got going on there.

Thanks!  Its nice to get my hands dirty on my own car but I'll leave the welding of the parts we sell to my certified guys.  It has been a fun project but I'm looking forward to being done and driving it!  Next up is to modify the roll bar mounting points and make a seat mount.