Winter Build 2019-2020: Top Flite P-51 (0.60 size)

[willsonman]

So here we go:

So, for those of you who don't want to sit through 9:23 of thorough explanation I'll give a brief rundown of this project.

@AkimboGlueGuns planted a seed in my brain that blossomed into diving into my engineering skill set. There have been a couple of great examples of constant speed/variable pitch propellers posted on social media however, the application of this in a warbird is complicated due to the spinner back plate interfering with linkage that would control the pitch. I've spent the past couple of months working this problem and have arrived at the prototype stage and parts for final assembly have arrived... more on that later.

The livery (color scheme) is currently being held close. It's not a secret but it is meaningful to me and I will get into that when the time comes.

In addition to the challenge issued for myself, I'd really like input on what the community would like me to do on this build. I've covered a myriad of techniques and topics in the past but this is an opportunity for new observers to chime in on what they would like seen covered in a build. For those who are veteran observers (and cheerleaders ) I welcome your input as well. There are soooo many things I can do now that I thought I would leave the canvas open for YOU to give input on.

As the list currently stands, we have the following suggestions:
Incorporate a whistle of sorts to simulate the howl this aircraft produces in full-scale (@earthsciteach )
Properly sequencing gear doors (YT comment from Bob Buesking)
wheel brakes to aid in differential brake steering
LED lights for the guns (FB comment from Jeff Williams
All internal linkages (@Mid7night )

Lastly, I want to be clear that this is NOT a sponsored build. I've been blessed in the past to work with exceptional people in the industry and have used some really great hardware. My goal is to focus on the community aspect of this build and in order to facilitate this, I needed to eliminate responsibility to deliver to the sponsor. I hope this will be a build heavily influenced by the community and something that every one of those contributors can look forward to and be excited about.

 

[willsonman]

In moving forward with the “front end” of the aircraft, I received a couple of critical components over the weekend. One of which is the motor for the project. I’ll be using Flite Test’s new monster radial motor as the power plant. I’ve been beta testing this motor and have been very impressed with its performance. I can confidently say that it’s easily on-par with an Eflite Power 60 motor. I have already taken the motor apart to remove the shaft in preparation of installing the front assembly.

In the kickoff video, the mechanism is using a PLA print of the hub I designed for the mechanism. The key for all of this to work is to have a hollow motor shaft that contains a push rod to control the prop blade pitch. Heli hubs for 4 blades are hard to come by let alone ones that will work with an 8mm shaft. With the PLA prototype working so well, I had one printed in aluminum from Shapeways. This part is printed using a laser that melts aluminum powder layer by layer and you are essential left with an aluminum part that is as strong as a cast part. The process leaves a gritty texture so I used a wire wheel on my dremel to knock some of that off. It fits my shaft perfectly and I proceeded to drill and tap the holes. Drilling out the pilot holes revealed no voids in the print and tapping was flawless.

 

[OliverW]

So here we go:

So, for those of you who don't want to sit through 9:23 of thorough explanation I'll give a brief rundown of this project.

@AkimboGlueGuns planted a seed in my brain that blossomed into diving into my engineering skill set. There have been a couple of great examples of constant speed/variable pitch propellers posted on social media however, the application of this in a warbird is complicated due to the spinner back plate interfering with linkage that would control the pitch. I've spent the past couple of months working this problem and have arrived at the prototype stage and parts for final assembly have arrived... more on that later.

The livery (color scheme) is currently being held close. It's not a secret but it is meaningful to me and I will get into that when the time comes.

In addition to the challenge issued for myself, I'd really like input on what the community would like me to do on this build. I've covered a myriad of techniques and topics in the past but this is an opportunity for new observers to chime in on what they would like seen covered in a build. For those who are veteran observers (and cheerleaders ) I welcome your input as well. There are soooo many things I can do now that I thought I would leave the canvas open for YOU to give input on.

As the list currently stands, we have the following suggestions:
Incorporate a whistle of sorts to simulate the howl this aircraft produces in full-scale (@earthsciteach )
Properly sequencing gear doors (YT comment from Bob Buesking)
wheel brakes to aid in differential brake steering
LED lights for the guns (FB comment from Jeff Williams
All internal linkages (@Mid7night )

Lastly, I want to be clear that this is NOT a sponsored build. I've been blessed in the past to work with exceptional people in the industry and have used some really great hardware. My goal is to focus on the community aspect of this build and in order to facilitate this, I needed to eliminate responsibility to deliver to the sponsor. I hope this will be a build heavily influenced by the community and something that every one of those contributors can look forward to and be excited about.

Oh yeah! Once I finish my current build I plan on building their 0.60 cessna 182 I have stashed away...

 

[AkimboGlueGuns]

Good to see some of my ideas get traction, lol.

@willsonman

There are a few things I KNOW you can do better than most other Mustang builders out there, among them being the gun placement. A lot of kits, ARFs, and BNF P-51s fall into the trap of a simple piece for the gun barrels. On the real P-51 the inner most gun on each wing was placed further aft with the barrel contained almost completely inside the blister on the leading edge. Most other Mustang models do not display this correctly (and it irritates me more than it should) but the ones that do are always the nicest models. Another thing to note is the operation of the rear radiator scoop control. At high power settings it is usually retracted into its least open position. This is what gave rise to the Meredith effect in aerodynamics. Because of the high air pressure at the front of the scoop was passed through the hot radiator it would expand, and without the necessary reverse flow pressure to force it back through the inlet it would expand and pass through the outlet like a pseudo jet, producing an additional 300 lbs of thrust. For this to be scale on the model at high power settings the hatch should close up. Most modelers I have seen have this reversed in there models. Very VERY excited to see this prop in action. Great work as usual!

 

[willsonman]

Interesting. In all the research I've found there is VERY little appearance difference on the inboard guns. While what you are saying is true...
http://www.denniskoleber.com/p51-mustang/p51-final-shots-068/
Many other reference photos do not show really any difference in the blisters...
https://www.alamy.com/stock-photo-wing-mounted-machine-guns-p-51-mustang-fighter-plane-50477449.html
Still, the muzzle is VERY slightly different on the inboard gun in every case.

I agree with you on the radiator scoop. I was planning on linking the scoop to the throttle just as you describe. It should be nearly closed at WOT. I'm still searching for some additional reference photos but Adam Drain could probably get me what I need. Come to think of it, @earthsciteach recently had the opportunity to CLEAN and FLY in one and I should have had him snap a few detailed photos of this.

I've gotten more nods to do flashing GUNS with and LED sequencer. I've also gotten a suggestion for airsoft guns... No, Just no. So I guess it is worth reiterating that I am not a big fan of weapons of any kind. While I appreciate the scale fidelity some try to focus on in this area I am just a hard one to sway in this regard. For those that recall, I did get a LOT of criticism for entirely deleting them from my Corsair build. It was intentional and then I was accused of a double-standard by having a bomb drop. I did not repeat that on the P-47 build. If you'll notice, every time I put it on display, I used drop tanks and not bombs. While I do have bombs for the P-47, it is something that I just do not want to focus on. The aerodynamic challenge of bombs that drop PROPERLY is fun. I also want to note that my favorite airplane is a dive bomber and it's sole purpose was to drop, well, bombs. It's a complicated stance to take and I liken it to those who oppose swastikas on German airplanes. Some are more sensitive to the detail than others. I'm still reconciling my stance on guns for this project.

Another suggestion is sequenced LEDs for the exhaust ports. I think this is a much more worthwhile endeavor. Minimal weight impact on a fun little gimmick that really would never be seen.

 

[Joker 53150]

Along with those exhaust lights (not to be confused with gun lights), some model train exhaust smoke mechanism to create smoke at startup would be nice.

 

[willsonman]

I moved on to doing assembly of the hub assembly. I started by removing grub screws and marking the holes so that I could grind flat spots for the final assembly. I also was able to cut the motor shaft to length. I beveled the edge and the entry hole where it was cut. I then got the grip arms disassembled and cleaned the bearings with a degreaser and then with 91% IPA. A fresh coat of grease was applied to these and red thread locker applied to the bolts prior to installing on the printed aluminum hub. Thread locker will be applied to every single screw on this assembly as it would be otherwise dangerous should anything back out. The key thing here is that you need the bolts snug but not too tight so that you are not compressing the bearings but not loose so that the grip arms wobble. You also need them all at the same approximate torque. A lot of time spent there.


Moving forward, I put on the modified swash plate and initially used 3-in-1 oil to lubricate but ended up using more grease there for smoother motion. I also installed a collet on the aft end of the motor shaft to keep the motor bell in position. I used a syringe to shoot grease into the hollow part of the shaft and then greased the push rod before inserting it for the pitch control. With that done, the whole motor assembly was complete. I need to go through and do a full cleaning of the motor bell to make sure any metal shavings are removed from magnets and do a final set of the grub screws. And to be clear, yes I am using the new FT monster radial. My beta testing of this motor has proved it to be a very reliable and powerful motor.


I'll be working on a test stand of sorts to clamp it into my vise and proceed with dynamic testing. I did take video during this entire assembly process as I'm sure it will prove useful for others to comprehend how the mechanism works.

 

[willsonman]

Along with those exhaust lights (not to be confused with gun lights), some model train exhaust smoke mechanism to create smoke at startup would be nice.

Yeah, smoke on electric models has been a problem for some time now. I've looked at SOOO many options over the last couple years and nothing seems to really be a good solution. If I'm going to have a system, it's going to work all the time. Otherwise, IMO, it is just not worth the weight penalty.

 

[chris398mx]

I moved on to doing assembly of the hub assembly. I started by removing grub screws and marking the holes so that I could grind flat spots for the final assembly. I also was able to cut the motor shaft to length. I beveled the edge and the entry hole where it was cut. I then got the grip arms disassembled and cleaned the bearings with a degreaser and then with 91% IPA. A fresh coat of grease was applied to these and red thread locker applied to the bolts prior to installing on the printed aluminum hub. Thread locker will be applied to every single screw on this assembly as it would be otherwise dangerous should anything back out. The key thing here is that you need the bolts snug but not too tight so that you are not compressing the bearings but not loose so that the grip arms wobble. You also need them all at the same approximate torque. A lot of time spent there.
View attachment 146075

Moving forward, I put on the modified swash plate and initially used 3-in-1 oil to lubricate but ended up using more grease there for smoother motion. I also installed a collet on the aft end of the motor shaft to keep the motor bell in position. I used a syringe to shoot grease into the hollow part of the shaft and then greased the push rod before inserting it for the pitch control. With that done, the whole motor assembly was complete. I need to go through and do a full cleaning of the motor bell to make sure any metal shavings are removed from magnets and do a final set of the grub screws. And to be clear, yes I am using the new FT monster radial. My beta testing of this motor has proved it to be a very reliable and powerful motor.
View attachment 146076

I'll be working on a test stand of sorts to clamp it into my vise and proceed with dynamic testing. I did take video during this entire assembly process as I'm sure it will prove useful for others to comprehend how the mechanism works.

Not sure if it is just my browser, but your pictures are not view-able on my computer.

 

[willsonman]

Yeah, seems fine on my browser. I'm using chrome.

 

[AkimboGlueGuns]

Interesting. In all the research I've found there is VERY little appearance difference on the inboard guns. While what you are saying is true...
http://www.denniskoleber.com/p51-mustang/p51-final-shots-068/
Many other reference photos do not show really any difference in the blisters...
https://www.alamy.com/stock-photo-wing-mounted-machine-guns-p-51-mustang-fighter-plane-50477449.html
Still, the muzzle is VERY slightly different on the inboard gun in every case.

A lot of P-51s that are still flying have the M-2s removed and are replaced with storage areas, so the barrel poke doesn't appear. It is very slight, but a pet peave of mine since it doesn't show up on most models. The exhaust lights would be an AMAZING addition. At low RPM settings the fire is super visible and it'll be amazing to see that in a model.

 

[willsonman]

The exhaust lights would be an AMAZING addition. At low RPM settings the fire is super visible and it'll be amazing to see that in a model.

Yeah, while considering this I'm kind of on the fence as flashing lights alone are going to have minimal impact alone. The addition of sound would help the effect to make more sense but I was really disappointed in the sound system on the P-47, despite my best efforts to make it as good as it could. For this reason, the idea is still on the fence but leaning toward a no.

 

[chris398mx]

Yeah, seems fine on my browser. I'm using chrome.

All good now on the pictures.......not sure what was up yesterday.

 

[willsonman]

Kind of an odd afternoon/evening at home so I neglected to snap pictures. I performed a thorough cleaning of the bell of the motor to remove any metal shavings from the magnets. I used tape to stick to the larger parts and then a bit of 409 to keep things clean and stick to the smaller bits. I bolted on the X-mount and decided for a giggle I'd run up the motor a little.

I decided not to go too crazy and leave off the blades and power up with a 4S pack. A quick run-up revealed that the grease from the control rod inside the hollow shaft caused a bit of friction as the grease was still wearing down. In conjunction with the friction of the bearing on the pitch (swash) plate, the push rod needed nuts on both sides of the mount to keep it from unscrewing during operation. Once installed, I spooled up the motor assembly holding onto the x-mount. Operation was smooth and balanced with linear movement of the control rod also being good. The pitch of the hubs was consistent with the tension of the spinning motor but I think I'd like to explore that more when the blades are on. Still, the hub assembly held in one piece with no sign of weakness... so far.

Next up is to make a proper mount for the motor and a corresponding servo to control pitch. I'll snag a better receiver so that I can monitor the ESC telemetry signal. It will tell me RPM, current use, etc. so that I can start gathering data without and WITH the prop blades. Overall a very promising start.

 

[willsonman]

As a brief update, well as brief as can be anyways...

I've made a mount for the motor along with a servo to control pitch. I hope to do some proper initial testing this evening... including a test with the blades on.

So the plan moving forward with the project is now... complicated. I'll post a video of the assembly and a separate one for testing. I will also shoot a video with an update to let you in on the very sudden complication. The shortest story is I need to pack up my entire shop and get all of my airplanes out of my home. And by pack up the shop I mean literally everything needs to be removed from the room.

 

[rockyboy]

I will also shoot a video with an update to let you in on the very sudden complication. The shortest story is I need to pack up my entire shop and get all of my airplanes out of my home. And by pack up the shop I mean literally everything needs to be removed from the room.

Aaackk!! Good luck with dealing with the crisis (I'm sure it's bigger than the hobby related impact). If you need any help, give us locals a shout.

 

[willsonman]

I appreciate that. Fortunately I have my club. I have space for my nicer builds in a secure location and other shop items can be temporarily stored in our field shed. Lots to work out but it will be an eventful couple of months.

 

[willsonman]

Still trying to find time to edit video. So, I'll just mention that the aforementioned complication with the build is that we are going to sell our home. As part of the process to list our home, I'm emptying the entire shop to show the home. Packing a well-established shop is a process as well as making all of the OTHER preparations. As I'm not sure when the actual move will take place it is therefore impossible to say when the build will pick back up.

 

[rockyboy]

Darn "real-life"(tm) getting in the way of hobbies!

Here's hoping your next house has an even nicer workshop!

 

[willsonman]

Update: Our house is sold and we are under contract for a new home. Move will be at the end of December. Once moved and settled a bit it way take a bit to get a new shop situated. I'll be evaluating the continuation of this project for the duration of the build season or not. First event is SEFF at the end of April/beginning of May which does not leave a lot of time for this project to be done right. I may proceed with a smaller project or two but I'm still debating this. I have a Top Flite red box F8F Bearcat that could be finished as well as a DARE design and engineering FW-190 that would be good projects to complete in this smaller time frame.