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Considering the amount of time and money you've invested in this model, getting the undercarriage cast in brass  would be worthwhile I think.  Alistair from Aerocraft Models gets his undercarriage cat in brass - maybe worth a chat with him.

 

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3 hours ago, AlexM said:

cCRcnCJ.jpg

 

Based on what I can see, I think that the greatest danger to the collapse of the landing gear will be located here, either at the top end next to the horizontal part of the steel rod, or (in my view less likely but still possible) at the bottom of the hole where the vertical rod will be connected.

 

The first failure will be the result of shear forces in the plaastic next to the rod, while the second failure type would be a result of poor bonding between veritcal steel rod and plastic, allowing the steel rod to slide into the plastic.

 

If (as I think you are doing ) the same idea is used in the bottom part of the 'u-shaped' part of your landing gear (i.e. a horizontal rod through the axis of the wheel) an this sits to the side of the vertical rod you again create a weak spot susceptible to shear forces.

 

Then again, as long as your shear forces are well below the Young's modules for the plastic you use you will be all right.

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Thanks guys!

 

1 hour ago, jenshb said:

Considering the amount of time and money you've invested in this model, getting the undercarriage cast in brass  would be worthwhile I think.  Alistair from Aerocraft Models gets his undercarriage cat in brass - maybe worth a chat with him.

 

 

I think you are right, if everything else fails, a metal landing gear would be a reasonable investition. Meanwhile, I provisionally pluged the steel-rod-enforced legs and the small support struts into the the designated openings in the wheel wells for a first test. And right now, it looks promising. Not bending visible :frantic:

 

UQj9n8J.jpg

 

JaknQvS.jpg

 

I'll leave it like this for a while to see if it stays stable.

 

Cheers

ALex

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Thanks, Mark!

51 minutes ago, jenshb said:

When I look at the breakdown of your parts, there is a weak spot where the two steel rods do not meet.  An alternative is to make your core our of brass rods that can be soldered to form a continuous strong core.

 

I know what you mean. I printed the parts with a resin that is advertised to be very strong. After all parts were glued together, I put some more liquid resin at the seams and put it under UV light to cure. Now, It's more or less one single resin part with steel-rods within. I'll watch it for some time and hope that is stays stable, especially at the weak point you mentioned.

 

One nice thing is that the balance can now be checked to prevent tail sitting. Until now, the necessary counterweight at the area forward of the main landing gear has only been roughly calculated. Now, with most weight-relevant parts provisionally attached, it already stands like it should. And the resin engines and the forward landing gear isn't attached yet, so I think at least regarding that aspect I'm safe. The weight on the nose landing gear will be minimal, so a fully printed nose gear without metal-rod-enforcement should be fully sufficient.

 

weToKHE.jpg

 

Cheers

Alex

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1 hour ago, Learstang said:

As always, most impressive work, Alex! Nice to see her on her feet!

 

Regards,

 

Jason

 

Thanks, Jason!

 

1 hour ago, D.B. Andrus said:

How about trying something like this using wire and stainless steel tubing:

 

Looks like you could print for the interior openings and have a strong and good looking gear with a stainless oleo.

 

Cheers,

D.B.

 

 

 

 

I regarded a 2mm hard spring steel rod as necassary.  But I was in no way able to bend one single rod  tight and precise enough at the three 90 degree corners.

Now thinking about it, I guess a combination of steel tubing with 2mm inner diameter as connector, 2mm spring steel rod sections for the straight areas, and some more easily bendable 2mm rods (brass?) for the corners, all jacketed with printed resin halves, could work and would be much stronger than my recent effort.

 

Let's see, maybe I'll give this a try. Until now, the model stands stable on its legs..

 

Cheers

Alex

 

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there is a 3D printing outfit that could do the gear in stainless steal.   Xometry.com  They do great work.  you send the drawing and they will give a quote online.

If you use them,tell them I sent you

 

Bruce Radebaugh

 

I'm having them do a 1/32 B-29 cockpit (nose to pressure bulkhead.

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Excellent work as usual, Alex! I wanted to have the landing gear legs for my Viking to be metal sintered but that costs a small fortune - I think the price was around €75 for a single landing gear leg. Printing them in castable wax and having them cast by a goldsmith could be a good idea. It'S my plan for the Skywarrior landing gear at least. 

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