500 size CH-54 Tarhe (Skycrane) Build

[F106DeltaDart]

This will be my build log of the Buamodel 500 size Skycrane. The model is sold as an S-64 firefighting variant, but I wanted to convert it back to the military CH-54. One of the big challenges there was fitting the mechanics. The stock setup hid most of the Trex 500 mechanics inside the suppressant tank. With that tank removed, there is very little space left in the upper spine.

To solve this, I designed a compact frame that uses parts from the Trex 500X and 500ESP that is about 40% shorter. Still need to shorten the mast a bit, but it seems feasible. Will be running Vario 530mm blades on a custom 6 blade head.

[F106DeltaDart]

Test fitting payloads and playing with mast tilt on the 500 size CH-54. The photos with the tail rotor attached have no mast tilt, and the one without has 1 deg fwd mast tilt. Right now I’m planning on 1.5 deg fwd tilt. Less than the scale tilt, but should produce a roughly correct hover attitude.

One of the distinctive features of the crane is the huge tail rotor. A standard 500 size tail rotor (72mm blades) looked way too small. After some calculations and experimenting, I found that 104mm KBDD tail blades gave me the closest appearance. And the great thing about those blades is that they are extremely easy to re-shape since they are plastic. I decreased the chord of each blade by about 30% and re-shaped the leading and tail edges with a small belt sander, then re-balanced them. I’ve done this a few times to replicate scale tail blade shapes, and it has always worked great.

[Blackhorse6]

Lookin' good Dart!

[F106DeltaDart]

Quick test fit of the Vario 530mm blades

[F106DeltaDart]

Adventures in 500 size 4 blade tail rotors…

Over the last year I’ve been working on getting my Skycrane up and running. The tail rotor has been one of my major trouble points so far, but I think I’ve finally resolved it. Here’s my lessons learned from the process.

As a note, both the Buamodel Skycrane (and now MH-53 as well) run Trex 500 mechanics, but are big (for a 500) fuselages with stretched tails. Both of mine will be swinging 530mm main blades as the standard 425s looked pitifully undersized. However, this also means the tail rotor diameter needs to be stretched. Both the CH-53 and CH-54 have large tail rotor diameters relative to other helicopters. So, thus the adventure began.

Currently, there is only one 500 size 4 blade tail on the market (STASRC), and it swings 470 size tail blades (69mm). It’s smooth and runs well, but running scale sized standard tail blades (104mm+) was out of the question. So, I decided to pursue other 4 blade tails with wider grips. I ended up testing a lot of options, with results listed below:

PKM 4 blade tail (discontinued)- Initially, this looked good and uses 4 of the standard Align 500 tail grips. However, the grips spindles were misaligned and it was unusable.

DEAO 4 blade tail (discontinued) - Notchy bearings, lots of friction to move.

CNC Helicopter 4 blade tail (discontinued) - Bad pitch slider. The tail grips and hub were true and smooth. I ended up mating this tail with the DEAO pitch slider to create a hybrid that worked pretty well. However, like the DEAO tail, it used ball links to go from the tail blades to the pitch slider. This created a lot more friction in the pitch linkage then I wanted. The standard align tail has a direct bearing supported connection and could be moved effortlessly.

This led me back around to option #1, the STASRC tail rotor. It was smooth and I’ve used it several builds without issues. However, how could I fit larger blades? I decided to buy some 155mm main blades from Microhelis and see if I could make them fit with some trimming. Sure enough, they fit right in, and they are a fiberglass reinforced plastic, so they were easy to cut down to scale diameter and balance! So I finally was able to achieve correct diameter, and an acceptable amount of friction in tail linkage.

Hopefully this saves someone else a bit of head scratching on their next 500 size build!

[Jim Jacobs]

Very cool build can’t wait to see you fly it

[F106DeltaDart]

Maiden flight completed this morning. Still need to do a bit more FBL tuning, but it will be on to detail and paint work soon!

[Jim Jacobs]

That’s awesome

[F106DeltaDart]

Got in about 15 flights so far. One of the things I hadn't addressed yet was the castoring nose wheel. For all the flights so far, it has been free to caster with no centering springs. Of course during startup, the aircraft always yawed a bit and I had to taxi to get the wheel re-centered. On my last flight, I applied full tail rotor during spool-up to minimize the heading drift. Wrong move... I stripped out the 45 deg gearbox as it got to flight RPM, luckily still on the ground. No damage noted on the airframe.

2 of the 3 gears in the gearbox were stripped and it was also evident that they needed to be shimmed. The mesh as-is was definitely loose. I ordered some 8mm shims, and after some trial and error, got it shimmed with a much better mesh. Also changed out all the bevel gears for Align parts. I am also adding the centering springs to the nose wheel before the next flight, which will hopefully occur tomorrow.

[F106DeltaDart]

Bevel gears have been successfully replaced and shimmed. Also added a nose wheel centering mechanism. Had a great time flying today at B.E.S.T. (Best Electrics in South Texas) at the Tri County Barnstormers Field in New Waverly, TX. The Skycrane is flying well, and the next steps will be working on the cargo release system, and painting/detailing. Possibly some revision of the tail rotor pitch linkage as well.

[AlmostReadytoFly]

Awesome build DeltaDart. Can’t wait see the finished product! Have always loved the Skycrane, especially the firefighting variant. Can you please advise how you obtained the kit? Would love to build a Skycrane. Did you contact Buamodel through his Facebook page? What system does he use for payment. Thanks for any info you can provide!

[F106DeltaDart]

Awesome build DeltaDart. Can’t wait see the finished product! Have always loved the Skycrane, especially the firefighting variant. Can you please advise how you obtained the kit? Would love to build a Skycrane. Did you contact Buamodel through his Facebook page? What system does he use for payment. Thanks for any info you can provide!

Thanks! Yes, I contacted him through his facebook page. Paid through bank transfer (western union). Not ideal, but I've ordered 4 fuselages from him with no issues. He asks for 50% up front, and 50% after completion. Expect that it could take a few months for him to build it (everything is made to order). Buamodel also makes the 6 blade head. It's a bit of a 1 at a time custom job, so expect that its almost as expensive as the fuselage and could take longer to make.

The other option if the payment makes you uncomfortable may be to send a message to Tyler Gray Models. He imports the Buamodel S-51 fuselages and may be able to add a Skycrane into the mix.

[AlmostReadytoFly]

Thanks for the info! Always been a fan of your builds. People like you really move the scale side of this hobby forward!

[F106DeltaDart]

Work continues preparing the Skycrane for Helistorm. Spent pretty much all of yesterday doing CAD modeling of the IBFs. Also designed and printed the fore/aft gear fairings. Will be doing the aux external cargo hooks next, as well as running a whole lot of brass to simulate the Hyd lines and control tubes.

Also, added a few photos from September where I flew the crane at the annual electric event in St George, UT. At that event, I suffered an IGB gear failure on spoolup. No damage, but had to change the gears and some procedures to prevent that from happening again. After adjusting shims and redoing the tail pushrod mechanism a few times, I’m satisfied that I will have robust and precise tail control this time around.

[Major_Rob]

What an amazing build! I was Army, our unit had two of the CH-54s, I flew Hueys / Crewed, ending up with about 1000 total flight hours. This was at Ft-Wainwright AK. Both helicopters were stationed in Anchorage. It was a treat to see them fly to Ft wainwright, an amazing helicopter that has an amazing history. I have a few questions if you have a moment:
1. What are you finding that your Main Rotor RPM works best?
2. What motor and packs are you running?
3. What ESC did you go with?
4. Are you running any sort of flight stabilization, GPS, Gyro, etc.
5. Now that you have the tail rotor sorted, do you find that your tail rotor authority is reliable, or do you find that you have to fly around your tail rotor?
6. Regarding the tail rotor driveline, the mass of the tail rotor hub and blade holder is substantial. The amount of torque that tail rotor is capable of is substantial. Are you finding any sort of twisting or deformation is taking place when you have used a large amount of tail rotor input while at flight power.
7. Do you have an estimation of what type of payload the heli is able to lift.
8. What limitation do you enforce on flying the heli, example max bank angle 60 deg, flight time XX minutes etc.
9. Do you have an autorotation bearing incorporated in the main shaft.
10. Finally, do you have any plans for the heli. Are you planning to show the heli. Or are you planning to just enjoy your incredible build any fly it.

Thank you in advance for your time, and the inspiration for the build!

Rob-

[F106DeltaDart]

What an amazing build! I was Army, our unit had two of the CH-54s, I flew Hueys / Crewed, ending up with about 1000 total flight hours. This was at Ft-Wainwright AK. Both helicopters were stationed in Anchorage. It was a treat to see them fly to Ft wainwright, an amazing helicopter that has an amazing history. I have a few questions if you have a moment:
1. What are you finding that your Main Rotor RPM works best?
2. What motor and packs are you running?
3. What ESC did you go with?
4. Are you running any sort of flight stabilization, GPS, Gyro, etc.
5. Now that you have the tail rotor sorted, do you find that your tail rotor authority is reliable, or do you find that you have to fly around your tail rotor?
6. Regarding the tail rotor driveline, the mass of the tail rotor hub and blade holder is substantial. The amount of torque that tail rotor is capable of is substantial. Are you finding any sort of twisting or deformation is taking place when you have used a large amount of tail rotor input while at flight power.
7. Do you have an estimation of what type of payload the heli is able to lift.
8. What limitation do you enforce on flying the heli, example max bank angle 60 deg, flight time XX minutes etc.
9. Do you have an autorotation bearing incorporated in the main shaft.
10. Finally, do you have any plans for the heli. Are you planning to show the heli. Or are you planning to just enjoy your incredible build any fly it.

Thank you in advance for your time, and the inspiration for the build!

Rob-

Thanks Rob, and thank you for your service!

1. I'm running around 1500RPM
2. 4000mah 6S batteries and a scorpion 3226 900KV Motor
3. Hobbywing 120A Platinum v4 ESC in gov Sto mode, spool time maxed out for slow start (25 sec)
4. I am running an ikon2 FBL unit. No GPS or other aids outside of the FBL.
5. I've had no tail authority issues so far in flight. One issue I've noted is that on initial rotor spoolup, it can castor the nose wheel a bit if you aren't ready for it.
6. Hard to say in flight. On the ground I don't see anything noticable.
7. Guessing 1-2 lbs? Need to do some flight testing there.
8. I usually fly about 6 min or so. I've got telemetry, so I just land when the steady load hits 22.2V. My flight limitations are very general keep it scale. I wouldn't do anything much over 45 deg. The battery hatch is held on by magnets and would likely go through rotor if one ever rolled inverted.
9. Yes, it has a Trex 500 autorotation bearing
10. Just fly it and get in-flight pictures. I've got several payloads I'd like to be able to pick up/drop off with it. An M2 Howitzer, M551 Sheridan, Apollo capsule simulator, and an RC duece and half truck. All except for the truck are 3D printed.

[iFLY_RC Vic]

Where is the LIPO installed? How do you get it in and out for charging?

[F106DeltaDart]

Where is the LIPO installed? How do you get it in and out for charging?

It fits vertically in behind the scale cockpit. The hatch is magnetically attached. This does result in the crane being a bit on the nose heavy side, enough that I’ll likely need to add tail weight.

[F106DeltaDart]

More Skycrane progress over the weekend.. Blades are finally painted. Took a while to get all 10 blades (6 main, 4 tail) masked off and painted. Now to get the rest finished in time for Helistorm..

[F106DeltaDart]

More weekend progress on the build. Lots of effort into the engine detail. Has been a combination of traditional scratchbuilding and 3D printing. Most of the fuel lines were done with 1/16” aluminum rod.Got the ladder steps done as well in brass, some of the rivet work (~50%) and got the windshield glued in. Still working on the cockpit and the rest of the rivets. It’s slowly getting there!