3D print for the Main Armament Gator/Bellows

[John Clarke]

While discussing some 3D printed handles on my build topic, I mentioned that Mark Hawkins can print flexible prints with very high detail too. It got me thinking, could the MA bellows be printed in such away that it would flex look and move like the full size bellows?

With some guestimated wish dimensions I asked Mark to see what he could do.
The bellows came out really nice, flexis slightly but nowhere near enough, even though the wall thickness is only 1mm thick, the wall of the bellows is too ridged to compress. We may try again with different wall thicknesses to see if we can improve the flexibility.


The print as is, would make a perfect replacement for model supplied bellows for those not wanting recoil movement as with a static model.
If anyone's interested, let me or Mark know.

May also be suitable for a static Challenger2

Remember.
If you need a fine detailed print of something, ask Mark, he maybe able to draw it up and print it for you. He drew the drawing in a few minutes which is faster than I could find a pencil.

The original

IMGP1010.jpg (73.89 KiB) Viewed 3103 times

[Clive Armitage]

Thank you for this information

[Vince Cutajar]

Those homemade bellows look great.

Personally I would use them even if they don't flex that much. I would make the inside diameter slightly larger so that during recoil the bellows would just slide (and not compress) over the barrel. I would remove two bellow sections and make the outside diameter of the bellows slightly larger just for looks.

Vince

[John Clarke]

I think I know where your coming from Vince.

The idea to replace the supplied bellows (50mm diameter) add multiple ribs/corrugations and reduce the overall diameter to somewhere around 40mm, then it should look like the original and sit between the "horns"

Had the barrel not had a thermal sleeve it would have been so much easier. But the bellows sits in between the canvas cover and the thermal sleeve, one will crush on the recoil which ever end it grips to the barrel if left as a fixed length . We might get away with a little movement on the canvas cover, so we need to get a little more flex on the bellows and a possible reduction on the servo arm controlling the recoil.

The recoil on the real thing is very short when viewing film clips.

Marks going to have another go with a different resin, which is apparently more flexible. That and maybe thinning the print, then it may have enough flexibility to work..

It's all experimentation at the moment.

BTW, it take 5 hours to print and a bit more time to clean up.

IMGP5626.jpg (43.22 KiB) Viewed 2972 times

[David Battson]

Hi John,
This is an excellent modification. I hope you can make it work, I've not found anything off the shelf that comes close to looking right.
Following up on Vince's idea, if the inner end was fixed to a floating sleeve which slides over the barrel and buts up to the elevation trunnion then it wouldn't transfer any force to the canvass cover.
David

[Adrian Harris]

If the bellows cannot be made soft enough, a slightly less prototypical method (if this is possible with the Chieftain) would be to fix the inner end to the turret, so that the barrel disappears inside the bellows, rather than compressing them.

Not quite the effect needed but it would look good when not firing, which is 99% of the time and hopefully people are looking at the sparkly lights in the muzzle rather than the bellows

Adrian.

[John Clarke]

It may not be as bad as first thought. The actual recoil is short, and the canvas cover could be made to cope with the compression and by extending the end of the bellows tube by say 20mm, 30mm total to pass through the canvas ring, there should be enough movement. 10mm outside compression 15mm on the canvas, you'd hardly notice.
The bellows needs to be anchored to the barrel next to the thermal sleeve otherwise it will crumple the thermal sleeve, not a good look.
I think I was a little naive thinking the flex of a print would as flexible as the full size Bellows and still have long term reliability. I even thought of gluing stitching 50 pieces of thin rubber together. Hummm, not really practical
I've been working on the original printed piece, cleaning out the internals as much as possible with a Dremel nylon brush attachment. It is now more flexible and compresses a little more, but it needs more effort than I would like to put on the servo.

So, when the new resin solution arrives (It ain't cheap) I'll ask Mark for an extended tube, going for the slide idea and we'll see how it goes.

As for a static solution. The original print is perfect.

[Mark Heaps]

For those unaware, the bellows and the canvas cover worked together as a seal against entry of NBC agents helping the NBC pack to maintain over-pressure within the tank.

[andymusgrove]

Nice idea John.

3d printing is so awesome and getting better and better. I’ve had an FDM Printer for years and it’s still awesome, the materials available are getting better as well.

Fingers crossed the new material will allow a little more flex. Can you thin down the wall thickness a little ?

Be interested to see how you get on.

Cheers
Andy

[John Clarke]

Ok, this is where we are.

The extra flexible resin printed Bellows has come out really good. Mark has done a fantastic job in such a short time.
The extended end tube was added which can be trimmed to suit if necessary and the number of ribs/corrugations was corrected to the number counted on the best photo I have 23, not 25 as originally printed. Oh yes and the wall thickness is down from 1.0mm to 0.8mm.
I can't guarantee that the flexibility of the print is as soft as the supplied Bellows, that has only 7 ribs/corrugations and is 10mm wider, but this is as good as it gets scale wise (Unless someone knows better ).
Printing time and clean up is around 9 hours now and of course more resin solution is used to support the larger print.
Cost of finished print will be £25.00 inc postage Uk, outside Uk POA, America, hold on to your lugnuts
I won't be holding any stock due to the price. So it will be on a first come, first served basis.
I can't thank Mark enough for the time he's put into this little project. If you have any thing you want to print with in reason, send him a Pm.

This picture shows the original first print supports and what you can't see is the print supports inside the print too. So though a hollow print lots of resin is used to support the shape while printing.

bellows print.jpg (56.41 KiB) Viewed 2741 times

IMGP1010.jpg (73.89 KiB) Viewed 2741 times

[Steve Norris]

Hi John
That’s a must have, put me down for one please.
Regards
Steve

[andymusgrove]

Hi John.

Put me down for one as well please.

Cheers Andy

[John Clarke]

Both noted, cheers.

[John Clarke]

The final new print is here. Four have been ordered so far. The new print is certainly more flexible than the first print, but I still think for the recoil action, the extended end will still have to slide into the canvas cover for much of the movement.
The pictures show the difference between the two prints, where more of the sleeve can be slid into the canvas cover.
Some of the sleeve may need to be trimmed depending on the canvas cover made by the individual modeler.
Mark has to order more resin, as it only seems to come in small 500cc amounts during next week, printing will then commence.
Apparently it's quite a messy procedure removing the innards but he will clean it all up to make sure it's all good before sending out.
As said before it takes time to print, but I think it's worth it. I will only ask for payment once I know the print has been completed.
Thanks for your interest.

[Mark Heaps]

Hi John, please put me down for 2 and let me know cost & how you would like payment. Will not need them for a while so postage to my father in the UK.
Mark