MinusAndy

MOC Fairchild A10 (WIP) pics added

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9 minutes ago, MinusAndy said:

I did look into a central drop tank but it would have to be far too big to fit the battery box in. There’s a couple of other parts that I felt could be upgraded too so this rebuild was inevitable really. My desk already looks like a crash site so it’s time to get back into it.

Another option would be to hide the batterybox in a stand. That way you can show off the working landinggear etc. without having to hold the plane in your hands.

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I also considered having a ground support vehicle with it in but I decided ages ago that I want this hung from my ceiling when it’s done. 

I now have this gearbox built and powered by two l-motors. The grey output is constant and will run the engines and the gun. The yellow and black outputs are switchable for direction and run the landing gear and flaps and slats.

New gearbox with constant drive out of the centre shaft to run the engines and the gun. Bi directional switching on the outputs to each side of that for the undercarriage and flaps and slats. Motors are hidden within the wing roots.

 

Edited by MinusAndy

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A quick update on this. I’ve ended up entirely rebuilding the gearbox and switches, after exploring several mechanisms that used intricate timing of levers to disconnect the landing gear and flap mechanisms I have finally used differentials as a way to turn off the power input to the functions when the limits of movement are reached. I’ve also incorporated a large main spar which runs right through the model in order to keep the wings nice and stiff. I’m trying to keep my part count down as I have a tendency to overbuild using tiny elements rather than using frames and long lift arms instead.

Main spar and revised gearbox and landing gear.

 

Main spar and revised gearbox and landing gear.Main spar and revised gearbox and landing gear.

in this final picture you can see the drive from the gearbox to the landing gear going through the output shafts of a differential. When resistance is met by the output the rotation is diverted through the crown wheel to the rotary selector catch.

I shall update this again soon when I’ve built the other wing and added the nose wheel. 

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I haven’t posted on here in ages, I got the a10 to a point where I couldn’t get the landing gear mechanism to work reliably in the way I want to so after several iterations of the gearbox for the landing gear I have decided to go down the pneumatic route and already the advantages are clear. So much part and hence weight reduction, which at large scale is vital I think.

I’ve built the nose section and wing root. The cockpit and controls are laid out, front undercarriage and door are now working perfectly using a single short piston.

52347928536_d028b05bf9_b.jpg

Revised cockpit and now pneumatics for landing gear.Revised cockpit and now pneumatics for landing gear.Revised cockpit and now pneumatics for landing gear.

I have a question regarding pneumatics: I’ll be building a pump that runs constantly using the same motor that runs the gun. I have an air tank (which is what the A10 is)

if I run the pump constantly is there a way to vent extra air from the system as I assume it will keep building until a pipe pops off.

thanks for reading and any help would be appreciated.

andy

Edited by MinusAndy
Added pics

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2 hours ago, MinusAndy said:

 

if I run the pump constantly is there a way to vent extra air from the system as I assume it will keep building until a pipe pops off.

 

I have never had such issues, so I think your good, maybe someone else will say differently though.

It is good to see you still working on this, I have been following it for some time now.

This thing will be an absolute masterpiece when finished, considering all the work you have put into it, I know what it's like to tear down a half completed build just to rebuild it better, enjoy.

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Yeah, I find that when using the small pumps, they'll just give up somewhere between 20 and 30 PSI, and just slip after that. I suppose you could add some kind of relief valve by hooking up a small cylinder to a valve, with a rubber band keeping it closed. If you got it tuned right, you could make it so that once the pressure got high enough, the cylinder would extend against the rubber band, open the valve, bleed pressure, and then shut it off again via the rubber band. It would be kind of like the auto-compressors people sometimes do, but with the opposite purpose! I've never gotten those compressors to work as well as I'd like, so I probably wouldn't try this. It'd probably be nasty to make reliable, and all the friction in the valve would be a challenge.

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Thanks folks. I think I’m going to put a clutch in front of the pump so I can disconnect it if necessary.

@Johnny1360 I don’t doubt there will be another strip down before it’s done!

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I believe there's an internal relief valve inside the pumps, exactly for this reason. Motorized pumps start to vent excess pressure in only a few seconds at most, without popping any hoses.

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