TR2/3/3A TR3A Seat cushion height?

[CraigLandrum]

What is the proper height of a TR3A seat cushion both in front and in back? My old rusted-out spring-based seat cushions measured 7 inches in front from the edge piping to where the side material curves under the bottom of the spring frame, and on the back, measures 4.5 inches from the edge piping to the spring frame. I can't use the old springs and for cost reasons have decided to use foam but wanted to get close to the proper dimensions. I do realize that the cushion domes a bit above the piping, but the piping seemed the best reference point.

So - can anyone confirm these front and back measurements or supply the correct ones?

Also, if anyone out there has cut their own foam for seats, I would appreciate some tips - especially on the cushion. Did you cut the cushion to slope backwards from 7 inches to 4.5 or what? Are the left and right sides cut with a slight inward slope or is this achieved using upholstery batting around the edges? I've seen the helpful set of pics that showed a set of foam seats being constructed with heaters but the pics didn't state any dimensions and it wasn't apparent that the foam was cut on a slope.

If nobody can supply any tips, I'll assume that I need to cut a sloped cushion with the above dimensions and then provide extra padding using upholstery batting to get a tight looking fit.

 

[DougF]

I would slope it. Use an electric carving knife.

 

[PeterK]

Craig,

I'm the one that posted the foam picture with the seat heaters. The foam is high density upholstery foam - two pieces of 5-1/2" thick foam glued together, NOT sloped, but carved on the sides and front to match the profile of the original spring seat bottoms. <span style="font-style: italic">edit: I compressed the foam on mine until I matched the slope of the original. Then stapled it to the baltic-birch seat bottom. </span> I didn't make the foam; I bought it precut and shaped to fit. Cost was around $100 per pair. Good foam is not cheap. They sit nice and firm, not bouncy, very comfortable.

To determine the height, I measured the old seats and they were flat front to rear. I think the height was around 6-1/2-7" but I'd have to measure my seats to be sure.

The batting is used to smooth over the corners under the seat covers, same as on the original seats.

To get the proper height from the 11" or so foam, I installed the covers then flipped the seat bottom over and used my knee to compress the foam to the desired height while I stapled the cover across, then 90deg and across again. Then inbetween eachstaple, removed the first four staples, adjusted and stapled again. It takes a good while to get them right going round and round back and forth across. If the cover wrinkles between the staples, removed one, re-stretch and re-staple until it's right. But once completely stapled, I trimmed the excess seat upholstery.

 

[CraigLandrum]

Thanks Peter - exactly what I needed to know about the foam. I would welcome any other seat cushion measurements from other members to get a general consensus.

 

[martx-5]

Your original measurement of 7" x 4 1/2" is very close to what my newly covered seat cushions measure. Mine are 7" in the front to the piping, and closer to 4" in the rear. There is a belly up in the center section. I have the original springs, and they did compress some when I installed the covers. I also have that horsehair stuff over the springs and some cotton batting over that.

 

[Tinkerman]

Craig, I used 4 inch foam cut to a pattern I made from the original seats. I bought two pieces of foam and after I cut them to shape I glued them together. Total cost for the foam was $120 from a local upholsterer. I got much info from martx-5 and thankful for that. I started out with 8" in the front and 4" in the back. Note that there is an offset between the front and the back. I used the 8 inch as a starting point, suspect I will be at about 7.5 inches before I'm through. I am using the original spring frames, but not the springs. I will use wire ties to hold everything together. Notice the "I will" haven't done it yet and that may change. I am still trial fitting with the seat cover and yes I have the horse hair stuff which I will put on after final fitting is complete. I will be using hog rings as per the original, mostly because I have them and the installation tool. Suspect Art's plywood systen would be easier. I got the horse hair padding on ebay.

Good luck, Tinkerman
Any questions PM me.

 

[PeterK]

This is my foam seat page that Craig refered to. The top left image shows the foam set as I received it:
https://mysite.verizon.net/kentech0822/triumph/tr3seats/

 

[Tinkerman]

I should add that I also got much help from Peter. Didn't mean to leave you out Peter. :-(

Using Peters system to make the tack boards for the seats.

Tinkerman

 

[PeterK]

Didn't feel left out at all. Glad I was of help Mr T.

 

[NickMorgan]

Craig,
That is the second time I have had to go out to the garage this evening with my tape measure!
I get 6 3/4 at the front and 3 1/2 at the back. These are the original springs with covers that were fitted about 30 years ago! I suppose that it is likely that they have sagged over the years, although they look right in the car.
I think you should also think about how much the foam is likely to deform compared with the springs. My seats go pretty flat when I am sitting on them. I am not that heavy, but I am tall, so I am pleased to sit low in the car. I have been in a TR2 with very solid seats and I felt as though I would slide straight out over the top of the doors when we went round corners! And my head was sticking up over the top of the windscreen!
Nick

 

[CraigLandrum]

Thanks for all the great info! My ultimate goal is to create a set of full size patterns and instructions for sewing your own TR3A seat covers (horizontal pleats). To that end, I carefully disassembled the intact older seats (which may have been replacements themselves) stitch by stitch. I then noted which panels had 1/2-inch cloth-backed foam tacked on the back (all the cushion top panels and seat front panels) and how it was attached. I then removed the foam and carefully ironed all the panels flat while the wife was out of the house and I could have a chance of cleaning the iron before she returned I then laid the panels on pattern making paper and traced each panel, making copious notes. I then scanned the tracings in 8.5x11 sections at 200 dpi and reassembled them in a Mac image editing program, cleaning them up and deskewing. These rough raster images were then imported into Adobe Illustrator where I used the scanned images to draw vector illustrations and type in my panel-by-panel comments. I then overlaid a 1-inch background grid on the image (so I could verify that the printed patterns were exactly the right size) and divided each panel into page-size chunks, removed the now unnecessary raster scans and converted it all to PDF. This got me a PDF document that when printed, trimmed, and assembled with scotch tape, got me exact paper patterns that I could use to cut my parts out of the 40 mil UV resistant marine vinyl I am using for the interior. I then worked out the sewing and assembly sequence and got to work.

I've finished sewing the covers for one seat and the patterns and instructions I've worked out seem to be dead-on. I took pictures of the sewing and assembly steps I used and plan to bundle all of this (instructions and patterns) into a PDF that I can post for others on the forum to use. This is the first time I ever touched a sewing machine and I am sort of shocked at the results I've gotten. So I would venture that if I can do it, others with more talent could do an even better job. I anticipate another two weeks until I can post the document since I'm doing all this on weekends.