The title of this article is specific to the TC but the application is generic to front leaf springs on the beam axle cars.
The original front springs on the TC were made by Brockhouse Berry of Manchester. Fortunately, TC0750 (‘The Vicar’s Car’) still has the original front (and rear) springs, so it has been possible to examine them really well.
The first observation is “they don’t make ‘em these days like they used to!” Take a look at the rear of the spring which takes the bush and shackle pin:
Notice how the ‘eye’ is formed in the original spring (‘eye’ on right) compared with the modern manufactured spring. The ‘eye’ of the original spring is perfectly round; modern replacements can be out of round.
Now take a look at the front ‘eyes’. Admittedly this is not the best of ‘shots’ but I can assure you that the ‘eye’ on the right (which happens to be a re-manufactured J2 spring) is distorted, whilst the ‘eye’ of the spring on the left (from TC0750) is round:
The other obvious difference is in the finish to the ends of the leafs. Modern re-manufactured spring leafs are cut square at each end so that there is a tendency for the leafs to “dig in” to each other as they slide. The leafs on the original springs are very nicely rounded and chamfered to avoid this happening.
So where does this leave the beam axle owner who wants some good quality springs?
Well, you can ask some questions of your spring supplier. You can ask what material has been used for their manufacture. EN45, a silicon-manganese-carbon alloy steel, is a recommended steel for suspension springs. You can also ask where they have been made. If the ‘eyes’ on your springs are out of round, particularly the front ‘eye’ so that the front pin is not a good fit in the ‘eye’, you have every right to send them back and get a refund.
A recent project which I have been involved in with Eric Worpe has been arranging for the manufacture of new front main leafs for the TC. Eric has been very much the driving force behind this project and has done most of the work.
We figured that if ‘out of round’ is an issue with modern replacement springs, then wouldn’t it be a good idea to get the front ‘eyes’ made oversize 5/8” instead of ½” internal diameter so that a bronze bush could be pressed in and reamed to the standard ½” standard size?
We ordered some SAE 660 bronze to make the bushes and five pairs of TC front main leafs. The chosen spring maker (Brost Forge, Unit 7, 149 Roman Way, LONDON N7 8XH – Telephone 020 7607 2311) has been in the business for a good number of years and has a working proprietor.
We also ordered a pair of complete front springs and these have been used as demonstration springs for this article.
At this juncture it is worth pointing out that the fitting of replacement main leafs is not worth it and certainly not recommended if the rest of your leafs are badly worn or sagging.
You will have noted my use of the plural “leafs”. Yes, I know that the plural of “leaf” is “leaves”, but this does not ring true to me in the context of leaf springs. Yes, I can sweep up leaves from the trees in the Autumn (the Fall) but I cannot lay out “leaves” of a leaf spring to photograph them.
One more piece of information before I forget; Brost Forge has a good size drawing of a TC front spring and also one of the original front springs from TC0750 to act as a reference.
Many new springs come bound up with paint, which has seeped in between the leafs and dried up solid. This alters the dynamic characteristics of the spring, resulting in an even harder ride and increased stress on the suspension. This should be rectified as follows:
We start by dismantling the spring; you’ll need to carry out this task whether or not you buy a new spring with oversize front ‘eye’ from Brost Forge. That is to say, if you buy a new spring, it needs to come apart – or if you are using your old spring it also needs to come apart to fit the replacement main leaf. The photo below shows the spring in the vice and the clips being bent back:
The next task is to run a 16mm HSS Co. milling cutter through the eye of the oversize scroll of the main leaf, truing it up to accept the press fit of the bush. Care must be taken to avoid opening out the spring eye by choosing the cutter direction to be the same as the ‘eye’s’ scroll:
It is now time to make the bronze bush and the top two ‘shots’ (overleaf) show it being made using the lathe. The bush is made to have an interference fit in the ‘eye’s’ scroll of about 0.4mm, so an outside diameter of 16.4mm (+0.1mm. -0.0mm) should be aimed for.
Then the bush needs to be pressed into the ‘eye’ of the oversize leaf, where it should deform to the shape of the scroll and then reamed to suit the fit of the front pin (1/2”):
Work can start on the leafs. The first operation is to round off the square ends and form a small bevel on the upper contact surface of each leaf:
When the work with the angle grinder has been completed and all the square ends have been nicely rounded they can be painted with Galvafroid (a zinc based paint) as in the photo below. This is a messy job, but well worth the time spent as the leafs will now be protected from rust:
The edges of the leafs and the flat areas of the leafs (where they do not overlap) can be painted with some black paint (see photo below):
It is nearly time to put the spring back together, However, before so doing it’s necessary to carry out one more task. If you thought that painting the leafs with Galvafroid was messy, this is a pig of a job! You need to coat between the leafs with a mixture of graphite and silicon grease or waxoil; reassemble the spring leafs and bend over the clamps, making sure that the dimples are in alignment. The graphite lubricates the springs, whilst the silicon grease/waxoil prevents water washing away the graphite mixture.
After assembly of the springs, force some of the mixture of graphite and silicon/waxoil into any gaps between the spring leafs. Some plastic gloves should be worn as graphite is truly messy stuff.
The photo at the top of the next column shows the task almost complete with the spring clips being bent back over. I found that it was a lot harder to bend the spring clips back over than it was to bend them back in the first place.
Note in the photo above the use of tie wraps to “clamp” the springs whilst the clips are being bent back over – whatever did we do before tie wraps came on the scene?
The final two photographs show a close up of the bushed ‘eye’ and the completed pair of springs.
At the time of writing there is one pair of bushed main leafs remaining at £65 the pair plus carriage (approx. £8 including insurance). If demand is there we could probably look to supplying another five (5) pairs. Enquiries please to John James (0117 986 4224).
Due to the amount of work involved we will not be supplying complete springs.