Custom Spacers for All Projects

So a little while ago I decided to take on my biggest project yet: a unique Hotrod build from scratch. The build will be fully unique and custom and will take a large amount of custom pieces. It occurred to me at the time that I would need a lot of time, space and ideas to make this a reality. I am planning on posting a few instructables as part the build, covering some of the unique ideas i have along the way.

One of the smaller things I realised I needed was spacers, sounds simple doesn't it! No, finding the right size spaces, with the right inside diameter and outside diameter at the right length is very difficult without having a machine shop make them and charging you through the nose for the privilege. The spacers are needed as I have a fully custom built rear suspension setup with custom hub mounts.

This is where I decided to make them myself. I looked at buying a lathe, I looked into having them cut from specific thicknesses of steel and a couple of other options until I decided to design them to the spec I needed, have them 2d printed and cast them using a hard rubber.

I designed 3 sizes, but then had an idea. At that point i needed multiple of the following:

12mm ID - 5mm and 11mm thickness

10mm ID - 13mm thickness

What I decided to do (as i realised I'm probably going to need more spacers along the way) was to print the following:

12mm ID - 5,6,7,8,9,10mm thicknesses

10mm ID - 5,6,7,8,9,10mm thicknesses

By doing this it gives me the ability to make any size spacer from 5mm upwards for both 10mm and 12mm ID's

This meant to get my 11mm thickness I use a 5mm and 6mm spacer together and similar for the 13mm.

The idea worked better than expected so I thought this would be a great first Hotrod build Instructable to start the "series"

To make this project happen, I needed the following:

• 3d printer or someone who can do this for you. https://www.ronanprintworks.co.uk/
• Silicone rubber https://www.benam.co.uk/
• A hard setting Urethane rubber https://www.benam.co.uk/
• Release spray, not super necessary but I find it helps. Can get this from Amazon
• Something to cast the mold in, that's big enough to fit the parts in. either use foam board or a plastic tub/wooden box
• Scales, something to mix with, something to mix in (measuring jug) and rice (will explain the rice in the next step)

To start the process, you first need to design what you need to mold. As I mentioned in the intro I needed a number of spacers at different sizes. I designed them as simple as possible as they are not on show or visible in any way and had them 3d printed. I used someone I found on FB Marketplace. You can contact him direct at https://www.ronanprintworks.co.uk/. Prices were really good, the prints were great and came super quick.

When the prints arrived I found a small wooden box that was a perfect size for all 12 of the small 3d printed pieces to fit into with a decent amount of space between them.

I used a small amount of double sided tape to secure them to the bottom of the box, bigger printed items may need something with a bit more holding strength, like hot glue.

I then used the Mold Star 30 Addition cure silicone. I have used Condensation cure silicone in the past so this is my first time using an Addition cure. I was advised to use the Addition cure instead and I was super impressed. It hardened in a few hours, was not tacky or fragile and hold its self really well. I got this from Benham.co.uk, the support was great, shipment was fast and the prices are great too. This is their catalogue https://www.benam.co.uk/catalogue, highly recommend them.

Once I had secured the parts to the bottom of the box i used an air can to make sure there wasn't any dust or anything at the bottom of the box and then got to measuring the silicone. THIS is where the rice comes in. This is a trick I learnt a long time ago. Simply pour the rice into the mold box with the parts to the point you want to fill the silicone up to. Pour the rice out into a jug and see what measurement you get. The silicone is a 1:1 ratio by volume so I add 10% on to the total of rice, half that number and and that gives you the amount of part A and part B you need for your mold.

Pour both parts into the jug (empty the rice first though) and mix together until you get a consistent color, be sure to get all area of the jug when mixing to make sure you mix thoroughly. When you have the silicone parts mixed well, you can use a degassing chamber if you want to, but this isn't necessary as the Mold Star 30 has a low viscosity meaning the bubbles basically make their way out by themselves, but tapping on the side of the mold to help this process when poured wont hurt.

Try to pour the silicone in one spot of the mold and let the silicone flow by its self, this will also help with bubbles. Now we wait.

De-molding is super simple, pull the silicone out of the container and do any clean up if needed. My mold came out really clean, there was a small amount of silicone that got under one of the 3d printed parts but other than that the clean up was super minimal.

I cleaned the mold with normal soap and water and the prepped for the 1st pour.

You could spend time working out exactly how much Urethane you will need for your parts but as the parts were small I estimated the amount when pouring it into a small mixing cup. For the urethane I used PMC790 Which has a shore hardness of around 90A which is similar to shoes heals and shopping trolley wheels and perfect for my application.

The ratio is 2 parts A to 1 part B by weight or volume so for the first attempt I poured a small amount and then upped the amount for the second pour until I had the perfect amount for each.

The process is very similar to the molding process, mix the correct amount of part A to part B, remembering the 2:1 ratio, and mix well. Again pour a thin stream of the mixture into one spot of the mold and let the Urethane push all the bubbles out. Now its time to let it set before de-molding.

The pieces will come out with a yellowy tint to them but this can be changed by adding a color pigment. You can get the pigments in most colors and these are also available at Bentley Advanced Materials | Mould Making and Casting Materials For Doing More (benam.co.uk)

As the color doesn't matter to me I didn't go with a pigment.

As I mentioned before I took the advice of the people over at Bentley Advanced Materials and I am glad I did. If you want to try this method or if this has given you some inspiration for something else you need for a project that you now feel you can make yourself. Let them know what your planning and they will help. There is also lots of material to read through and watch on their website and social media.

https://www.benam.co.uk/

https://www.facebook.com/BentleyAdvanced/?locale=en_GB

https://www.instagram.com/bentleyadvanced/

As always, any questions let me know and I will help where I can.

Happy building