The whole PB Racing range of car uses the same dampers, although the shafts used on the Dart are longer ones taken from a previous version of the 1/8th Diamond car. The older type 1/8th & 1/10th dampers had plain, non-threaded bodies, which are useful for implementing a double shock conversion on the Dart.
I have done a great deal of work on the shock absorbers and below are my observations and suggestions for building a better damper.
All of the parts are shown below and those that may need some minor alterations to ensure easy assembly and trouble free adjustment and/or maintenance are indicated.
All plastic moulded parts should have the flash (excess plastic left over from the injection moulding process) removed.
As they are very sharply cut, the threads on the top caps benefit from having their tops cut off as they can bind on the plastic threads of the damper body. I have found using a very sharp craft knife to shave the tops off the threads to be the most effective solution.
In direct contradiction to the original building instructions, I seal up the trunnion cap moulding holes. Although various people will disagree with this modification, my justification is that if air can flow freely in and out of the damper, then all you are really moving, especially with small suspension movements, is air.
They fit and they work, although the diaphragm from one of the Mugen 1/8th scale cars is a direct fit and has been fitted by some drivers.
See Top Alloy Cap comments above.
The adjusting ring can become tight part way down on the threads of the damper body. There is a high spot where the plastic is injected, which can be removed with a sharp craft knife
I build my rear shock absorbers using the shorter (33mm) shafts (12/529) from the 1/8th & 1/10th scale cars, as I feel that they place the piston at a better position in the body and do not fail due to running out of movement. The front shock absorbers use the standard shafts.
Some of the shafts I have used have the e-clip grooves cut at different distances apart and must have been from different production batches.
This was taken into account when I made some new pistons (see below). All shafts were polished before being assembled.
The clips are normally easy to fit (unless they go airborne!). Sometimes, though, the groove in the piston rod has been cut a little too deep, leading to a sloppy fit. Carefully closing the ends together slightly with a pair of long nosed pliers cures this problem.
See comments below.
After observing many pairs of dampers where the hole in the middle of the standard single hole piston had become deformed, I replaced them with a custom made two hole version.
This deformation was probably due to the fact that relatively thick oil is flowing through only one side of the piston, therefore creating an unequal lifting and pushing down of the piston.
If you Play the animated diagram on the left you will see a demonstration of what happens.
The two hole piston balances the forces out, as would the three hole piston (below left) already produced for the other PB cars.
See comments above.
These o-rings are among the best I have come across so far.
The standard bushes were felt to be a little small in both length and diameter. New ones were made from brass to the required dimensions.
The core diameter of the threads inside the cap are sometimes a slightly different size to those on the damper body moulding, making fitting the cap difficult. The only solution to this is to run an appropriately sized die up the threads of the plastic moulding. See also the Top Alloy Cap comments above.
Whilst it is easy and tempting to cut a slot into the spring retainer to make changing the springs easier, on the Dart this generally results in the springs escaping. This does not seem to happen on the Apollo and Black Diamond cars though.
It is easy to damage these rod ends when first threading them onto the shaft. I always partially pre-thread them with a 3mm tap.
After reading the above you should follow the PDF instruction sheet to arrive at an assembly that resembles the image to the left.
Although the above possibly seems a little bit extreme, there isn’t a great deal of damper for such a car as one the size of the Dart, so it really needs to be working the best it possibly can.
I do have in my possession a quantity of non PB alloy bodied shock absorbers that have progressively wound springs that are fairly easy to fit to the Dart. I will be testing these out when time/weather permits, but have further information if you are require it.
I am also aware of a number of different types of shock absorber systems that were tried on the Dart and Diamond cars. I will try to gather the required information and seek the permissions of the relevant people to be able to publish them on-line.