Interior... Part Deux

Sorry for the late update but learning to sew is not something that can be done in a hurry.

After much practice and a lot of planning it was time to get started. The decision was made to go with a diamond pattern which will give the seats a relatively simple but pleasing custom look without going over the top so to speak. More on that later in this update. The first order of business was to finish the modifications to the Juki sewing machine.

In the last update I mentioned that the machine needed to be slowed down. 5500 stitches per minute is fine for sewing clothes but is way too fast for upholstery and thick materials. The solution is to "re-gear" the machine and cut the speed by a minimum of 75%. Since this machine is powered by an electric motor which has only one speed there are a couple ways to accomplish this. You can change out the motor for one that is electronically controlled which is too expensive, or you can change the pulley ratios. I showed a picture last update of a commercially available pulley setup that will change the ratio but at nearly $100 it's too expensive. I figured I could build a similar device for about half that cost so.... that's exactly what I did.

The original ratio was 1:1 with the motor and machine both having a 4" diameter pulley. The best way to change this is to use a smaller pulley on the motor and a larger pulley on the machine. Unfortunately that can't be done because the pulley on the machine can't be switched out. In the last update I installed a 1 3/4" pulley on the motor which by itself slowed the machine down by about 60%. This was not enough as the machine was still too fast. To improve the reduction I made a simple intermediate pulley system from parts I picked up at our local Tractor Supply store. I added a 12" diameter pulley I picked up on E-bay and added another small 3" pulley which will directly drive the machine. This effectively reduces the speed by around 90% and makes it totally controllable for thicker materials. It now has a top speed of about 500 stitches per minute and with a light touch on the foot controller can be run at speeds as slow as 60 stitches per minute. The total cost of this modification was just over $55 and well worth the investment.

OK, with the machine now slowed down so a novice like me can handle it the next job was to install the foam on the seat frames. Last update I installed the burlap which protects the foam from the seat springs. The installation of the foam is a simple procedure and involves using hog rings to fix the foam to the seat. The seat bottom is the only part that used foam. The seat back called for using cotton batting. Again this was a simple procedure. I used three layers of cotton batting and covered it with a heavy duty fabric (duck cloth) and hog ringed everything to the frame. Unfortunately I have no pictures of this process. If you want to see examples of this procedure just do a search on YouTube and you'll find plenty of how to videos from Legendary Auto Interiors which show this process in detail.

With the foam installed on the seat bottom I used some scrap material my wife gave me to make a pattern for the vinyl that will eventually cover the seat. Each section requires its own pattern. On this seat I have two diamond stitch sections, a center section, two end pieces and a front piece along with two side pieces. Each section has its own pattern.

As the process continues eventually the entire seat bottom is covered with the appropriate patterns and all the witness marks are made to keep everything lined up once the vinyl is cut and ready to be sewn together.

The patterns are laid out on the vinyl and everything is marked and cut out keeping a half inch seam allowance all the way around. I decided to use a half inch seam allowance because it will allow enough extra material for a double backed French stitch. This will result in a very strong seam. Here is a French seam and if you look carefully you can see how a half inch of material is folded over on the back. This was just a practice piece but you get the idea.

With the vinyl cut the sections that will be diamond stitched were backed with 1/4" scrim foam also known as sew foam. This is a foam with a material backing that will hold a stitch. Without the material backing a stitch would pull right through the foam so don't think you can use any foam for this kind of handiwork. Here is the diamond pattern laid out and ready to sew. You can see the lines for the 1/2" seam allowance clearly in this pic.

After the diamond pattern is finished a center section is added and the two diamond patterns are joined together. You can see the back of the seams folded over in this pic. They are glued down using contact cement and before the French seam is finished another piece of vinyl will be added to the back of the seam which will double its strength.

This is a sample piece but you can see how the added strip of vinyl on the back doubles the strength of the seam.

Here is the same section top side. You will notice I did not use white thread for the stitching, only red. This was for a a couple reasons. First, I thought the white thread was a little "over the top" and second, using matching red thread will help hide any mistakes I make... and it did.

After the side and front sections are sewn in place I added a four layer thick piece of heavy duty fabric (duck cloth) to the back end of the vinyl. You can just see the edge of this on the back of the seat in this picture. This was double stitched in place and will protect the vinyl from tearing when the hog rings are used. The front section of the vinyl was folded over and a small piece of rope was sewn in place which will allow the hog rings to grab on to the rope and not just the vinyl. This basically does the same job as a listing wire, but since the front of the seat has some sections that are not straight a rigid listing wire can't easily be used. Again, if you want a more detailed explanation just google a video on the subject. I suggest you watch the Legendary Auto Interior videos. They are very good.

Here is the front section and you can see why a solid listing wire can't be used. There is the hump for the driveshaft and the two cutouts for the subframe connectors.

And finally the finished seat bottom. Not bad for an amateur, if I do say so myself. Are the seams all perfectly straight? No. Does it look near perfect from 3 feet away? Yes..... and near perfect is just fine as far as I'm concerned.

That's it for this update.Next I'll start the same procedure for the back of the rear seat. I expect this one to go a bit faster... at least I hope so.

Check back often for more updates...

Back to
Polara Home Page