We've had a lot of requests for more information on how our new plastic parts are manufactured, so we thought we'd offer some more insight!
The original moulds for the plastics on Armstrong and Harley Davidson MTs were repatriated by us in 2019 from the original company that had been contracted to use the moulds since 1985.
This is the original tooling that every piece of plastic was produced with. Obviously these moulds have had considerable use over the years, but we are refurbishing them as we bring each one back into service. Certainly the main critical surfaces are in good order and good for another 35 years!
Below is a picture of welding work being completed on an original 1993 gunbox mould, making it into a usable platform-mounted tool.
The process involves a split aluminium mould, rather like a jelly mould which is the mirror image of the finished product.
Plastic granules which have been dyed to the specific required finished colour are put into the mould, the quantity of which having been calculated by weighing a sample of the finished product and allowing a percentage for trimming.
The mould is then put into an oven set to a temperature level to melt the granules, and the rotary table inside the oven slowly turns as the granules liquify to coat the mould evenly. It is then cooled while still being rotated. The mould is then parted and the product removed.
There is obviously some trimming required to remove burrs and general mould marks. Some items such as side panels are made in pairs, then parted as part of the trimming process.
Of course this rotational moulding process is only really suitable for relatively low volume production, as the mould has to be manually separated each time, and by and large, only one product is in the oven at a time.
It has served the MT production well though and these moulds have been in routine use since 1985 and 1992 respectively.
The raw material granules for the fuel tanks differ from all of the other plastic products in that it is what’s known as “cross-linked” material.
It is this cross-linking in the structure of the polymer that gives the finished tank the required integrity and resistance to breaking down through exposure to petrol.
As well as the Armstrong plastics, all the plastic parts for the Harley Davidson were made here in the UK on these moulds, these were then shipped to York, Pennsylvania for assembly on the bikes.
We are really fortunate and proud to have this original tooling, and are constantly going through each one to refurbish them to ensure they are useable for the foreseeable future.
We hoping to be able to upload a video of the plastic manufacturing process sometime in the future to illustrate the operation further.
Thanks for taking the time to read this article, we hope you found it interesting!
We are constantly working on new plastic parts stock, so please search our website if there's a specific item you're after.