SEAT SPRINGS

I had trawled the internet to search for replacement seat springs for an LD 150 Mk 2.  There appeared to be new ones available for dual seats as fitted on the later models but nothing for my front and rear seats.

The original springs are 8.0mm diameter with a wire thickness of 1.6mm, 13 for the front seat and 11 for the pillion seat 

Whilst searching I came across a really good blog, "Lambretta LD Restoration" which had a very useful entry on seat restoration ( http://billy192.blogspot.co.uk/2011/11/stage-3-with-lambretta.html ).  He also had the problem of sourcing springs and had read of someone else making his own using a flexible drain cleaning spring from B&Q.

B&Q 6ft Spring Spiral Drain Cleaner  
Length 6ft  (1.8m)
cost about £7 
Spring diameter 5.5mm
wire thickness 1.2mm

Having looked at the B&Q spring I felt that it was too weak.  I discovered that WICKES have both a similar version and a heavier one.  This time I took my vernier calipers with me and found  the size to be closer to the original seat springs.

WICKES Adjustable Drain Cleaner
part No  W500594W
Length 4.7m
Cost approximately £15
Spring diameter 7.4mm  
wire thickness 1.4mm.

Note:-  this provided sufficient for all 26 springs and some left over.

 

With two options for the replacement springs I couldn't resist the temptation to check the spring rates, I didn't have much choice but I wanted to know where they were compared to the originals.  My test was simple, I fixed one end of the spring in a vice and attached the other end to a spring balance.  I stretched the spring 0.5 inches and noted the load on the balance.  Not very accurate but the results were as follows:-

                          ORIGINAL       11 lbs

                          WICKES          21lbs

                          B&Q                 8lbs

Despite the higher reading the WICKES spring felt best so I went ahead and started making the springs for the pillion seat. 

 The spring is supplied with both ends terminated ready for drain clearing.   Firstly cut off one of these ends in readiness to form the hook end for attaching to the seat frame.  I used a Junior hacksaw, whilst the spring material is hard it was possible to make one blade survive all the cutting.

 It's virtually impossible to form the hook with the material cold.  I used a small Servert gas flame which heated a limited area.  Firstly grip the end of the spring with pliers and pulling to start to open the coils.  Now apply the heat to the first couple of coils.  As the coils become red hot the coil opens out easily.  You can unwind as many coils as necessary to make the hook.  The only problem is how to stop without distorting the last turn in the spring.  With a little practice I got better (after 52 ends you have to).

Making a neat end also takes a little practice.  At first I did it freehand.  Later on I made a simple jig that allowed me to bend the wire more consistently.  The other end of the spring is made in the same way but it is necessary to look at which way round you want the hook to face.  This depends on how they are attached at each end 



In most cases the hook ends are at 90 degrees to each other so that when assembled the spring is not in torsion, only tension. I think there were only two positions where the hooks were in the same plane.


I was concerned that heating the end of the coil would result in the wire being left too soft. So much so that it would straighten out under tension.  I didn't want to have to re temper each end so I was relieved when this proved not to be a problem.  It will be interesting to see how the springs respond to use.

I noticed that whilst there were thirteen holes in the back frame there were only eleven holes in the front fixing.  There was an obvious space in the front fixing to accommodate the addition two holes so I went ahead and drilled them.  I have no idea why they were missing.

Pillion - Rear fixing

Pillion - Front Fixing - missing holes

The completed Pillion Seat

The Completed front seat