Reference: CMP seat back coil spring dimensions

[Alex van de Wetering]

Here are the measurements of the spring on my C8 1940 front seats.

Rings (9 per seat)
Wire thickness 3mm
Overall diameter 25mm

Centre springs (18 per seat)
wire thickness 1,5mm
40 coils
Outside diameter 9,5mm
about 85mm overall length including the hooks

top and lower springs (6 per seat)
wire thickness 1,5mm
48 coils
Outside diameter 9,5mm
about 94mm overall length including the hooks


The top 3 springs and lower 3 springs are longer than the ones in the centre.

Rings seem to be welded at the end....it's not solder as I heated one and nothing melted....except the skin of my finger

My seats don't have the springs as shown in Peter's picture (with one long hook)....maybe a difference in supplier at the time?? or Ford vs Chev? early vs late?

Alex

[Peter Duggan]

Hanno,

I never did find a source for new springs. I did acquire several rough seats and salvaged enough springs for my driver's seat, and a healthy reserve.

Alex,

Thanks for stepping in and correcting my post about the seat back springs. When I posted that picture, I was at the start of my learning curve. Your measurements and comments mirror what I have learnt.

Peter

2017-08-16 16.12.39.jpg

2017-08-16 16.20.32.jpg

[Hanno Spoelstra]

Thanks Alex and Peter!

I will start searching.

[Bob Carriere]

I am surprised Grant did not write on this topic....... just came back from a week of vacation and catching up with old emails.

We have found suppliers who will sell suitable size/tension springs by the yard but also got a bunch from a flea market already near size..... we used them with key rings which can be bought bulk.

We have found that some seats have flat 3/4 washers with four little holes drilled for the springs.... no idead if they are Chev or Ford.

will look up our information and post in a few days.

Bob C

[Grant Bowker]

The "by the yard" springs we found that were closest to the springs we were finding in seat frames for OD and wire size (and thus stiffness) were listed at McMaster-Carr, their product 9664K52 https://www.mcmaster.com/#catalog/123/1277/=193uptc
Oddly enough the springs were labeled as made in Australia so Australians may be able to more easily track down the source and not worry about McMaster's policy of not selling to those requesting international shipping or likely to take the parts out of the US. (so much for their argument about protecting US technology from intellectual theft).
To re-bend the ends for attachment to the frames and rings/washers, hand tools were adequate. The original(?) springs we found in the frames had similar (the short style in the photo posted by Hanno) hooks on each end (differences due to age and abuse?).

[Grant Bowker]

As follow-up----->. The flea-market find had the end flap of the box marked:
DURO DYNE
Fire Damper Hardware
FBBKP-39
Coil Spring
Quantity 50
Duro Dyne of Canada Ltd. Montreal
The spring was wound form 0.0495 or 0.050" wire (depends on where I measured) to make a 0.50" outside diameter coil, 2-7/8" between insides of the hooks, length of the coiled portion 2-5/32"

Durodyne still exists, still has a location in Lachine (part of Montreal) http://www.durodyne.com/ A quick check didn't find the springs on their website but I'd be happy to be shown the link.

[Jordan Baker]

Just looking to gauge interest in getting a run of seat back springs made from a local spring producer.

A set would be 6 long and 18 short springs. I'm not sure if they could also do the rings but I'll ask.

[Phil Waterman]

Hi Grant

Add enough for (two seat) sets for me if you can get reasonable price. Will check the other two trucks to see if either of those needs a set.

Cheers Phi

[Grant Bowker]

Originally Posted by Grant Bowker

The "by the yard" springs we found that were closest to the springs we were finding in seat frames for OD and wire size (and thus stiffness) were listed at McMaster-Carr, their product 9664K52 https://www.mcmaster.com/#catalog/123/1277/=193uptc

More information on "by the yard" springs - springs of the same dimensions (same size + same material = same force) as the McMaster listing given are available from Century Spring. Century's E-20 spring is dimensionally the same as McMaster's 9664K52. http://www.centuryspring.com/extensi...ings-e-20.html
Although their site shows an eye on the spring I would be surprised if the long length springs actually have eyes. Unlike McMaster, Century will sell to Canadians (although I had the springs I bought shipped to the UPS store across the line). Century's instructions for forming eyes on the end of springs cut from long lengths are attached. Century's spring #576 is similar in length to some CMP seat springs I have.

[Phil Waterman]

Hi David and Grant


David good simple approach I've got a fish scale, so I measure how much the springs stretch on my HUP when siting and leaning back then remove one and measure its pull strength at that pull length.


Grant that is quite a good instruction sheet you posted, looking at the instruction sheet an idea hit me wonder what the pull strength on screen door springs is per inch of spring length? Or would that be to simple a solution?


Will take photos as I explore this problem. One of my problems is that my Pattern 12 Driver seat doesn't recline as far as the passenger so it is hitting me high on the back instead of the length of the back. Probably will have to drive out the pivot point rivets and get it to move freely.


Cheers Phil

[Alex van de Wetering]

Attached are the rings and springs Hanno and I bought for our seats. Credits go to the Dutch Morris owner that found the suitable springs, as mentioned earlier in this thread.

Both springs and rings are Metric measurements, but they are pretty much spot on when compared to the originals, especially when you take production tolerances of the time into consideration.

I decided to use 1 type/length of spring, in stead of the 2, or sometimes 3, different lenghts used in the originals. I just stretched some of the springs to match the longer ones.....just put a screw driver in the vice; put one spring eye over the screwdriver, and use a second screwdriver through the other eye...than slowly pull and check against the original springs.

Alex