[MOC] Technic B-25 Mitchell WIP

[apemax]

Hey all.

Well I finally started work on my next Technic aircraft, A B-25 Mitchell. It's going to be a similar size to my Technic Spitfire and mostly the same type of functions. The planned functions I have at the moment are:

• Both engines powered by a PF XL motor each.
  
• Working ailerons, elevator and rudder all controlled from the cockpit.
  
• Working Landing gear powered by a PF M motor.
  
• Working Landing flaps also powered by a PF M motor.
  
• Working turrets.
  

I've so far built part of the left engine bay with the landing gear leg and the basic structure of the center of the main fuselage. First a couple of pictures of the engine bay:

Next up is the section of main fuselage I've built so far:

I am going to need a better control system for the control surfaces as the design I used in my Spitfire won't really work with this scale very well so if anyone has any suggestions on that front I would be very grateful.

I'm not sure how long this MOC is going to take as I don't currently have all the pieces needed and affording them is going to be interesting to say the least but I will try and finish it before the end of the year hopefully.

[Alasdair Ryan]

What about LAs for the control surfaces?

[apemax]

What about LAs for the control surfaces?

LAs are a good idea for the actual control surfaces. Thanks. I also need a better design for the joystick mechanism in the cockpit as I want it to be more like the real thing.

[Captainowie]

It's nice to see some more studless building. That thing's gonna be huge!

Any reason you're using XL motors for the engines? They seem like overkill for simply driving a propeller.

Regards

Owen.

[apemax]

It's nice to see some more studless building. That thing's gonna be huge!

Any reason you're using XL motors for the engines? They seem like overkill for simply driving a propeller.

Regards

Owen.

Yep it's probably going to be my biggest aircraft to date.

Mainly I'm using the XLs to get the propellers to the speed I want. You can gear a XL up more than a M motor because of the torque of the XL. I want the propellers to go as fast as possible just like I did with my Spitfire.

[Tommy Styrvoky]

Nice progress so far,what scale is it gonna be?

For control surfaces maybe worm gears or pneumatics or string.

Edited July 30, 2014 by Tommy Styrvoky

[rollermonkey]

I don't think you're going to be able to gear-up even an XL motor enough to make it taxi and/or take off.

Actually... Has anyone been able to even taxi a lego aircraft just with propellers?

[dhc6twinotter]

For the ailerons, I would suggest just running an axle down the length of each wing, similar to the 42025 Cargo Plane. For the flaps, you could use an axle running down the length of the wingspan turned by a worm gear, or you could use LAs to lower the flaps. Pneumatics may be an option here too, although you wouldn't get much precision. For the rudders, I would suggest a simple axle running to the back, or maybe push/pull rods (probably a combination since the B-25 is a twin tail). For the elevator, maybe either an axle running to the back or push/pull rods. You will need to use a friction pin, counter weight, or spring to keep the elevator in the neutral (middle) position when the control stick is not being held.

Sounds like a neat project!

[MrNumbskull13]

I don't think you're going to be able to gear-up even an XL motor enough to make it taxi and/or take off.

Actually... Has anyone been able to even taxi a lego aircraft just with propellers?

If taxiing is when the vehicle is pushed around by the power from the propellers then yes, I have seen it done with a buggy motor, shouldn't be too difficult to find on YouTube.

edit: cool project btw!

Edited July 30, 2014 by MrNumbskull13

[apemax]

Nice progress so far,what scale is it gonna be?

For control surfaces maybe worm gears or pneumatics or string.

Thanks. I think if my calculations are correct it's going to be 1:24 scale.

I think at the moment it's going to be either worm gears or mini LAs. Not 100% sure though.

I don't think you're going to be able to gear-up even an XL motor enough to make it taxi and/or take off.

Actually... Has anyone been able to even taxi a lego aircraft just with propellers?

Nah but I'm more going for looks than them actually moving the aircraft. That would be fun to try though...

For the ailerons, I would suggest just running an axle down the length of each wing, similar to the 42025 Cargo Plane. For the flaps, you could use an axle running down the length of the wingspan turned by a worm gear, or you could use LAs to lower the flaps. Pneumatics may be an option here too, although you wouldn't get much precision. For the rudders, I would suggest a simple axle running to the back, or maybe push/pull rods (probably a combination since the B-25 is a twin tail). For the elevator, maybe either an axle running to the back or push/pull rods. You will need to use a friction pin, counter weight, or spring to keep the elevator in the neutral (middle) position when the control stick is not being held.

Sounds like a neat project!

Thanks for the suggestions.

I used axles for the ailerons and rudder in my Spitfire and the only issue I found with them was there was quite a bit of play between the control stick and the ailerons/rudder. Just so we're on the same page when you say push/pull rods what do you mean exactly? I'm also having issues with connecting all the control surfaces to the control stick and peddles (For the rudder), any ideas on this?

If taxiing is when the vehicle is pushed around by the power from the propellers then yes, I have seen it done with a buggy motor, shouldn't be too difficult to find on YouTube.

edit: cool project btw!

Thanks.

[apemax]

I've done quite a bit of work on the B-25 so I thought I'd post another update and show what I've done since the first part. First up I replaced the left and right landing gear mechanism with a bit better design that should be a bit stronger and work a bit better.

This is actually the beginning of the right engine bay. The landing gear mechanism is a bit easier to see on this side as it isn't built up as much.

The landing gear in the down position.

Next I built the control stick and peddle for the ailerons, elevator and rudder.

As you can see this is more compact than the control system I built for my Spitfire.

I've only added one peddle for the rudder as to try and fit two inside such a small area would

be difficult so I thought I'd go for just one to make it a bit easier. I've also added the front landing gear as well.

Lastly a couple of shots of the overall progress I've made.

[Alasdair Ryan]

It's great to see someone using studded technic again in a moc.

[HarmanMotor]

Nice work so far! Have you thought about having a bomb bay with electrically-operated bomb bay doors?

[apemax]

It's great to see someone using studded technic again in a moc.

I've always found building studded to be a bit easier for me than studless. Thanks.

Nice work so far! Have you thought about having a bomb bay with electrically-operated bomb bay doors?

Thanks.

I've thought about it but I'm not sure whether there will be enough room once all the other mechanisms are in place. Will definitely try and add it if theres enough room.

[apemax]

Just a quick update today as I haven't gotten much building done in the past week. I did a bit of work on the tail section and I think I've come up with a design that should be quite strong once it's finished. It's also now getting close to how long it's going to end up being once finished.

I have actually run out of 1x16 studded beams so I might replace some in the tail with 1x14 studded beams.

And thats it for this update. Hopefully I get a bit more building done this week.

[tedbeard]

Looking forward to this. I got to climb aboard a real one the other weekend and then watched it take off from the tarmac.

[apemax]

Looking forward to this. I got to climb aboard a real one the other weekend and then watched it take off from the tarmac.

Thanks.

Thats awesome, Never actually seen one in person let alone been in one. That must of been amazing.

[tedbeard]

Never actually seen one in person let alone been in one. That must of been amazing.

It was pretty cool, and very cramped inside. I always picture "bomb bays" as huge but when they let us stand underneath with our heads inside it looked about the size of two large refrigerators stacked on their sides.

Now, if only I had had a spare $600 for a 45 minute cockpit ride... I was very jealous watching that takeoff.

[apemax]

It was pretty cool, and very cramped inside. I always picture "bomb bays" as huge but when they let us stand underneath with our heads inside it looked about the size of two large refrigerators stacked on their sides.

Now, if only I had had a spare $600 for a 45 minute cockpit ride... I was very jealous watching that takeoff.

Getting to fly in one, now that would be awesome. Size can be deceiving when you have only seen things in pictures. I remember seeing a Lancaster in person for the first time and being amazed at how big it was.

[apemax]

I've managed to get a bit more work done on the B-25 over the past week so I thought I'd post another update on what I've done. First of I've done a bit of work on the control system so now the control stick has all it's outputs and I just need to connect them all to the control surfaces which will be done once I've actually made the control surfaces.

These two outputs are for the ailerons.

The other part I worked on was the tail. I replaced some of the 1x16 studded beams with 1x14 studded beams and started on the very beginnings of the tailplane.

And finally the overall progress I've made on the fuselage.

[apemax]

More progress has been made on the B-25 in the past week so here's what I've done.

This past week I tried to focus on the placement of the motors for the landing gear and the mechanism to connect them to the actual landing gear. I also added the two main beams where the wings are going attach to.

This is the motor for the landing gear on the wings.

This is the motor of the nose landing gear.

And as usual a picture of the over progress, I'll probably work on the tail section a bit more and get the battery box mounted as well this next week.

[apemax]

Finally got some more work done on my B-25 over the weekend so here's what I've done. I've added the other side of the nose section as well as completely replaced the control mechanism for the elevator control to using beams as the original way of doing that (using axles) wasn't going to work. I've also run the rudder control mechanism to the tail as well although I haven't added the actual rudders in yet.

I also came up with a preliminary design for the top turret.

[apemax]

Another quick update today as I've made a bit more progress on the B-25 so here's what's been done.

The main thing I've been focusing on over the past few days is the tail section which as you can see is starting to look a bit more like the real thing. I still have a way to go yet but I've finally got the control surfaces on the tail working well so the only control surface left to get working is the ailerons which I can only to do once I've actually made the wings.

Something I forgot to put in the last update was that I had actually built the propellers. They are a similar design to the propeller on my Spitfire but smaller as this model is in a smaller scale.

Finally as usual a shot of the overall model.

[apemax]

I've got some more work done on my B-25 over the past week so I thought I'd post an update to tell you all what I've done.

I've improved the tail section a bit by adding beams going straight up the under side of the fuselage as well as building a bit more of the tail it's self.

I've also built a preliminary design for the tail gun.

Another thing I did was put in the battery box and IR receiver where they will go. I'm not 100% happy about how far the battery box sticks out the top but I'm not sure how to solve that one yet.

[Alasdair Ryan]

I would use a square battery box (less high),I know I am being picky but I am not a fan of different sized plates and the staggered bricks in the first photo.