[Tamar]

Posted 13 March 2019 - 03:39 AM

The Road to Le Mans 1/32: 3 weeks and counting
Just 24 days before the start of the first practice session in Henley in Arden. Looks like we're going to play catch up with Garage 27 for car prep.
We've had a good test session last weekend in which we managed to do a lot of work and testing, not everything I had hoped we could do, but it was a very, very constructive day.
First and foremost, we've now got a good base set up for the new MK2 chassis, that may look easy, but with a new chassis you basically start from scratch for 50%.
And one those test days..time flies. But I'm getting ahead of the story, more on that part in a later post, because before we could go testing I first had to finish some parts.
 
 
Bussy Bees and Lego time..again
Marc was going to bring the Dental Vacform machine to Best (thx Eric) so we could pull some lightweight windows, meaning that I had to prep the masters.
So here I go, its lego time again. Besides great for building the walls of your cast box, the little Lego pieces can also be used to support and fixate the position of the part you want to copy.
Most important when they're fragile breakable parts like windows, even more important when those windows need to be fitted from the inside of the body..to maintain the correct shape and fit.
On the left image you can see how I used some Lego blocks to build up a base. In the centre image you can see how I then applied the Modeling bees wax around the Lego base. (sorry, a bit out of focus)
You can actually see the top of the Lego sticking out of the bee wax.   
The Bee wax can be shaped cut and moulded with a knife, a spatula and even with your fingers. Its great stuff.
It gets softer when warm and can be dissolved (as in when you need to clean the master again) with cleaning petrol.
When building up the bee wax you need to pay attention to three things:
 
1 that you seal your master completely, because even with the tiniest  small gap between the master and the wax...the silicone will creep in between.
2 that you keep the master as pyramid shaped as possible.
3 that you maintain a clear definition on where your master ends, if needed you may need to go against the pyramid rule here, as long as the overhang is minimal.
 
After bee waxing its time to build the cast box, and the to clean your master, and I mean clean, polish and remove every flint or dust particle that you can find.
Because the silicone will copy anything, even the tiniest surface details like lettering on the window streamer or the tiny raised window frames that Scalex tamponed on the glass...
...which in this case isn't such a bad thing... but that too is for a later post.




Casting bubbles and how to get rid of them
I've covered casting the silicone before so I'll skip that part and head straight to the resin casting. Here (also due to time restraints) I used a very fast setting PU resin. 
Handy when you want to pour several casts in a couple of hours, but the down side of the fast stuff is... you've got a two minute window in which to mix the stuff and pour it into the silicone.
As with silicone casting the main thing to avoid here are air bubbles, they are unavoidable (well with out a vacuum pot they are) but there is a (quick) work around to get them out of the important parts...
.. and those would be detail parts like the thumbs and fingers of your driver or some delicate motor detail that took you hours to create on your master, or the bottom (and thus in the mould the top side) of your air intake.



So before you start mixing your resin, have you silicone moulds laid out in sequence of casting, have a fair amount of kitchen towels ready for the Oooops!  moments.
A spatula to wipe off the excess resin and most important..a couple of tooth picks. 
Now you can mix your resin, make sure you mix the minimal amount, as the more resin you mix in the cup the shorter your cast window will be. Don't worry about mixing too little for these type of masters.
Resin sticks to resin like....well that would automatically be corrected here on SF, but believe me it bonds very well. So even when your mould isn't filled to the edge, just mix a bit more and complete the casting.
So..about the work around to get the worst bubbles out...well its simple, as you can see in the pics above I use the tooth pick to pry them out of the deep parts in the mould.
Just stick it in the cast resin while its setting and wobble it around... sounds simple doesn't it ?...



...well off course it isn't that simple and it will take you several casts before you get it right as can be seen in the picture above right.
Took me several pours to get one air intake without some air bubble caught in the mould. But the windows and headlight lenses came out perfectly.
Ready for some Saturday afternoon vacforming.
 
Front suspension from quad pod to tripod
There was one more item that I had to fabricate for the MK2 chassis and that was a bracket to mate the Slot.it SW pod to the central front suspension mount we'd incorporated in the MK2 design.
We'd used a similar design last year with the C7R for which Stefan Kievit designed a nice 3DP part, but although it worked very well, that bracket needed to be dis mounted from the motor pod if you wanted to change the O2 chip.
For the Ford I wanted too keep it more simple, stronger and lighter. So I rumbled through my supply of GRP and cut this small (and if I may say elegant) bracket from a 1mm thick sheet.
A Big head tall Slot.it suspension screw, some spacers and a 2mm bushing, a short Scaleauto spring and a Thunderslot top nut.
The Slot.it SW motor mount had now been modified from a quad pod to a tripod with just on screw to set the front pod float, which can be done without taking the body off.
Now we were ready for some serious test runs. 


 
 

To be continued

with kind regards
Tamar