Showroom 6DOF Stewart AC Servo Motion Helicopter Simulator Build

Just before I finish the base, I wanted (as mentioned before) to assemble it all with rubber boots on the rod ends (i.e. heim/rose bearings).

I looked at many options online, and nothing I found made me happy and as far as I'm aware, there are no boots for the female version of the bearings. I'm sure they're out there but prohibitively expensive, or stupid delivery times.

I bought a few of the offerings, on offer, but they turned out to be IMO, rubbish.

So I'm working on this. It's not quite there yet, (I need to get the clearances closer to acceptable) but I've broken the back of it, and will tweak it tomorrow, before making a test mould.

I've bought a 2kgs of resin (to last over xmas), and a 1kg tin of liquid silicone rubber, so it's just a matter of a little more work.
I didn't want to finish the base and not be able to put it all together all greased up with dust covers.

More resin arrived today, but I did have enough to try a set of mold parts to explore.
First inner part (which I called the plug) I printed on it's side, as it doesn't like surfaces that eminate out into fresh air (well liquid resin actually) with no support, and although I added supports, it was a mess really.

The second was printed standing up, with stronger supports, which was quite successful.

The mold casing (times 2) printed just flat on the table, finished with no problems.

This exploration lead me to tweak clearances, make the sealing ribs larger and add a few more features.

I'm about to print another set of these, and attempt a first silicone pour.









I plan to assemble the mold, and pour in the silicone in the funnels (which enters the mold at the bottom, hopefully to eliminate/minimise any air bubbles), untill I see a witness at the four smaller holes.

If there is any problems with air bubbles, I will see if I can utilise my ultrasonic cleaner in some way to vibrate it? Well thats the plan anyway.

I am so impressed with the skills and drive that so many members here have. Fantastic work!

I haven't had too much spare time for rapid progress, but I have been snatching time between work and chores etc, to do some bits.

The dev stockpile is building up.



Quite a learning curve going on here.

I did a first pour knowing full well it wasn't going to be perfect, but I was keen to play with the silicone, to get a feel for what to expect.



My smallest container with measurements down the side was 60ml, and the catalyst was 3%. So guestimating the 3% and 3% of colouring pigment meant the silicone ended up taking a week to fully cure. Obviously I got it wrong, which prompted me to buy some pipettes.
Having struggled to brush the silicon grease on as a releasing agent, I was prompted to buy some spray on releasing agent.

The first pour was a disaster, the viscosity was such that I had to fill the sprule funnels and set the timer on my phone to 30 mins to come back and refill. After about 3 or four hours, teh remainder of the 50ml mix was begining to coagulate, so I called it a wrap.


It seems the parts are suffering from Z axis shrinkage, which I later found out after cutting the mold in half.
The black pen mark is almost touching the casing.

The printer is currently printing a casing with low shrinkage resin..

I'd say that's really promising results to start. Were you able to test fit what you made there or is the shrinkage too much making it too tight?

The shrinkage during 3D resin printing of the mould, made the wall thickness of the silicone rubber too thin.
Other issues were:

• The rubber boot orifices were to large and didn't grip the body of the rose/heim bearing, or the spacers. The diameters have been reduced.
• The rubber took too long to pour, so I have drilled out the sprule holes to take piston type plungers, to push the rubber through the mould, this will allow me to add more catalyst and speed up the curing time.
• The chosen shore hardness may be too soft.

I've tried to address these issues in the coming prints.

Almost there...
Two issues to sort.

• Force more rubber through the mould to expel the air bubbles (which seem to be at the beginning of the pour)
• Grind the inner plug to create a thicker wall at the side centre walls.

On first inspection as the mould was seperated, I was quite pleased with initial result, then I saw the air bubbles. The reduction of diameters meant the grip on the main body and spacers was adequate.



As this was not going to be useable, I thought I'd check wall thickness, and preceded to cut it in sections.



This highlighted the previous problem of printing shrinkage, and that the low shrinkage resin hadn't full solved the problem. The thickness in the area of the air bubbles was perfect.

I've decided to grind the centre plug because the FEP membrane of the printer vat is leaking and needs changing.

Ok, some progress. I am pleased to anounce the first successful bubble free silicone rubber casting.

The secret to getting rid of the air bubbles was de-gassing. (putting the rubber in a vacuum chamber after agitating and putting all the bubble in it.)

Now I started looking at all the kits on amazon, and was a bit reluctant to spend all that for 12 rubber boots.
So my search term included DIY methods. During my perusal at the various kits etc, I saw what to me looked like a brake bleeding vacuum pump, exactly like what I have on my shelf, I rushed off to find it and blow me down, it had a larger (than I was previously using) container. In fact the perfect size for the amount of rubber I was trying to de-gass (when under a vacuum the rubber rises up the container, and so needs to be at least two or three times the size of the volume you are trying to de-gass).

I'd not used it yet, so it was straight out the box. I did a test of the pressure, and after spraying a little WD40 down the pump shaft to ensure the seal was working efficiently, it reached the 29in Hg, as described in the YT videos.
With my multi-modified mould, I did a de-gass (amazingly easy) waited for 5 mins to make sure it was fully 'cooked' and released the vacuum. The smoothness compared to the airated version was amazing.

Images.
Mould - now with added barrier around the top, because when you push the plungers down the rubber comes out of the air vents and without the barrier just goes everywhere.









The smaller container was the original one that I was using, the larger one came with the bleed kit, which perfectly allowed the rubber to expand whilst de-gassing.





Now to do another 11

Just received these beauts yesterday....
I got fed up with so little progress, and instead of making them, I sent the model to an online CNC manufacturer.






I still need to drill & tap some bits as I wasn't sure what size I will be using, but thats broken the back of the job, and with a little more work they be ready to put on the base.