Espek DIY bases reloaded

[RonnyO.]

Hello to all!

Since I read this forum entry http://www.lejonklou.com/forum/viewtopic.php?t=396 quite some time ago I thought about doing some changes to my stock Espek bases.

I read through the entry carefully and got to know about the improvements that some changes to the bases could bring.

The only thing that kept me hesitating was the work itself and the needed preparation...

Where do I get the steel shots, which shots should I use, which resin and so on. If any one else wanted to upgrade his bases I will share my findings:

1.) Steel shots:
I was looking for quite some time because I am from Austria and the name steel shots is not quite common here. I found some resellers but they would only serve my request on commercial amounts (> 500 kg). Thus I visited ebay and found a reseller. I got to know that there are quite a view different qualities (nominal grain size) available. I chose the quality S280 with a nominal shot diameter of 0.7 mm with a range of - don't hurt me if I am wrong - 0.5 mm to 1.0 mm. I wanted the maximum shot diameter to be 1.0 mm. Do not ask me why but mainly because Ceilidh said that he used shots with a diameter of 1 mm.

http://www.ebay.at/itm/25kg-Stahlguss-R ... 2277wt_922

2.) Resin:
I had a little but not much experience with 2 component epoxy type resins but not all of them are good memories :) I really feared that the resin could be too viscous and the steel shots would not mix very well with the resin.

The other and much greater fear was that the open time of the resin would be too short to distribute the resin-steel shot compound evenly in the bases before the resin starts to harden. 20 minutes or less are quite a short time if you need to do something as accurately as possible. Another point to think about was the heat that would develop during the hardening process and the possibility of self-ignition if the layer thickness gets too high.

I was searching for a resin-hardener system with long open time and low viscosity and finally found this:

http://shop.r-g.de/Epoxydharze/EP-Giess ... rklar.html

It is from a German company and is sold in different trading units from very small (300 ml) up to larger amounts (>1kg). The real advantage is that it has an open time of 300 minutes. This means that you can easily mix one kilogram of the resin steel shot compound and work as accurately as needed because you do not need to hurry - otherwise the resin would start to harden. The resin needs 24 h to 48 h to fully harden depending on the layer thickness. In my case it took almost 2 days.

An advantage of the long open and hardening time is the very low exothermic character of the resin during hardening. The lower the exothermic character the lower is the mold shrinkage and the risk of self-ignition.

3.) Resin to steel shot ratio:
I tried to find out the "perfect" mixture between steel shots and resin. The shots and especially the gaps between the shots should be resin filled. I did some trials and found out that 7 g resin give a perfect mixture with 100 g steel shots. This mixture hardens to a compound that is covered with a little resin layer on top. This is just perfect to ensure that the resin is in surplus.

If a lot of steel shots are mixed with a big amount of resin (1000 g shots with 70 g resin) a lot of air gets mixed into the compound together with the steel shots. This is not problematic, but it seems as if too much resin was mixed with too few shots. You just need to cast very thin layers and give the air the needed time to escape from the casted layer and only top the old layer with resin if the bubbles on top of the previous casted layer disappeared.

4.) The result looks like this and sounds just like described by Ceilidh:

http://www.flickr.com/photos/69899535@N ... hotostream

Br,
RonnyO.

[jhumus]

Hi,

I'm really interested in modifying my standard bases too. I have been looking for a resin which is a relatively low viscosity liquid and has a long pot life. My plan was to pour in some of the resin and then add steel shot compacting the shot as i go. The resin I have found is,

http://www.resin-supplies.co.uk/help%20 ... 20Data.pdf

It's a polyurethane resin. Any thoughts on how this would perform regarding rigidity. Also any idea of the quantities of shot and resin I would need? Finaly how did you go about the process. Did you do one section at a time, pour the resin into the base and then add the shot or add the shot to the resin and then pour into the base?

Any advice would be very much appreciated.