Roban 600 Size UH-60 Blackhawk Build

[PawPaw]

Regrettably, I have nothing positive to report on my UH-60 Blackhawk build since my last post. In fact, prospective purchasers of any Roban 600 size conversion kit that includes replacement “drop down” frames, specifically the UH-60 and UH-1, should not consider them unless you have access to an original Align Trex 600ESP for the conversion. You will not get the spacers required to use a Chaos or PhoenixTech 600, even though Roban and MRC clearly states those Trex clones are a direct fit. After 3 weeks and several emails to MRC, no spacers….or even a clue as to a projected delivery date. Instead, I was offered a $12 account credit if I could independently source the spacers myself. Oddly, I ordered a 4 blade tail rotor directly from Roban in China on May 29th…a week after MRC said they ordered spacers…and Fedex will deliver the rotor on Mon June 14th. Go figure.
Luckily I have some rudimentary machine skills and will cut down some 1/4” aluminum plate for those spacers. Guess that qualifies as sourcing them myself?

[DCORSAIR]

Well that's too bad, I don't have any plans on building another Roban 600 size heli right now if I get the Cobra, so your spacers are in the mail on the way to TX..

[PawPaw]

Thanks, DC! I pulled the dimensions from the bearing blocks to mill the 4 I need so will return your 2 after I verify the fit.

[DCORSAIR]

Thanks, DC! I pulled the dimensions from the bearing blocks to mill the 4 I need so will return your 2 after I verify the fit.

You don't need to return them, I really thought it over and with Roban and MRC and the issue with stock supply, I don't plan on building anymore Roban helis as of now, I won't need them, with the Align ESP parts hard to find and the Chaos parts not in stock, looks like MRC has let the Roban kits sell out and only a few of those left, I'm not liking what I see for the future of scale helis. I want the Cobra and thats it for me for now.

[PawPaw]

I absolutely agree. The writing is on the wall and I’m finally reading it. Fortunately, I continue to have great luck dealing with Roban directly for support of the 6 Robans in my hanger but I have decided to look harder at the Vario models for future purchases….maybe turbine, even? 🤑

[DCORSAIR]

I absolutely agree. The writing is on the wall and I’m finally reading it. Fortunately, I continue to have great luck dealing with Roban directly for support of the 6 Robans in my hanger but I have decided to look harder at the Vario models for future purchases….maybe turbine, even? 🤑

Oh, would love to try a turbine one day, at least before I call it quits with this hobby, I tried dealing with Roban directly but I get no response back from them at all, maybe I'm getting a response but don't recognize the email or something, will message them again, I'm using their chat response.

[PawPaw]

I use the “contact us” button. They always answer within 24 hrs. I’ve never tried the chat feature. Then again, I’ve always bought something and never just asked a question. That may be the difference?

[PawPaw]

Finally some progress: bit the bullet and milled the drop shaft bearing block spacers from 1/4” aluminum so now have the tail drive component completed in the frame. I will emphasize, again, these spacers’ dimensions are critical for the drop shaft to run true in the tail drive housing as the stock top bearing must be removed to install the longer shaft. Don’t be tempted to substitute washers or collar bushings for the spacers here: support is needed full width of the bearing blocks. If you are willing to pay the $38 shipping for the $6 item Scaleflying.de has these spacers in stock.

[PawPaw]

Was kinda worried the 4 blade tail assembly I ordered from Roban would be too large since it’s the same one used on the 700 size UH-60 (5mm shaft for both) but it’s fine, I think. It’s just sitting loose in the opening for the pic and will be higher when mounted.

[PawPaw]

With the spacer/bearing block issue resolved was time to set the tail transmission umbrella gear mesh. This job is more complicated than normal because the entire transmission and both bearing blocks must be removed from the frame each time a shim is added to recheck the mesh. This is because the bearing blocks support the vertical drop shaft and can’t do so outside the frame. Using the supplied metal umbrella gears (recommended!) it took 6 shims to set the mesh correctly. I use white lithium grease on both gears to help visualize how the teeth are meshing as I turn the rotorhead. I will continue the lithium through my early test runs under power then switch to a higher viscosity grease when everything looks good.

[PawPaw]

Luckily, the 4 blade tail rotor assembly from Roban had been shimmed correctly at the factory so I didn’t need to address that. The torque tube elbow gear box cannot be shimmed, so time to test assemble the long and short torque shafts and tubes and mount the tail rotor. Everything feels smooth with the normally expected small amount of play in the tail blades from the elbow gear box and torque shaft spline clearance.

[DCORSAIR]

With the spacer/bearing block issue resolved was time to set the tail transmission umbrella gear mesh. This job is more complicated than normal because the entire transmission and both bearing blocks must be removed from the frame each time a shim is added to recheck the mesh. This is because the bearing blocks support the vertical drop shaft and can’t do so outside the frame. Using the supplied metal umbrella gears (recommended!) it took 6 shims to set the mesh correctly. I use white lithium grease on both gears to help visualize how the teeth are meshing as I turn the rotorhead. I will continue the lithium through my early test runs under power then switch to a higher viscosity grease when everything looks good.

I have shimmed all my big ones so far but just curious what you go by to tell you its properly shimmed??? I really don't know myself, I just add shims until I get the outside edges on the gears to line up evenly, seems to work but my Apache that I got from Gravy has developed more slop now that I have several flights on it, he had problems right from the start and since my purchase, I have added more shims, I think its hopeless really getting them perfect but my worry is when does a person replace them to be safe?? I use honey grease on mine, stuff is sticky and seems to be working good, I grease every two or three flights.

[PawPaw]

I add shims until I can just feel a very little back and forth play in the horizontal (main torque shaft) gear. I hold the autorotation gear or main rotor grips firmly with one hand, then reach inside the frame to see how much I can slide that horizontal gear back and forth. Should just feel enough to know it’s moving. I would add another shim if it shows more play over time…it will feel “locked” if you add too many. The white lithium will accumulate at the base of the teeth if set right but will be forced out if too tight. Never tried honey grease but sounds good. I use Lucas gun grease but it does fling off more than I like so hafta keep an eye on it.

[PawPaw]

Did Gravy shorten the torque tube on that Apache?

[DCORSAIR]

Yes, he did all that already, so next time I have the mechanics out I will go over it again to see what is wearing out on it, there is going to be slop no matter what we do, I mean we're talking about two gears in the 45 box with slop, plus the front gears, plus the rear tail rotor, and then the two torque tubes as well, I'm surprised they even hold up as long as they do, lol.

[PawPaw]

Yeah, unfortunately, can’t shorten the long torque tube as much on the elevated tail helis as on the straight ones like the OH-6. Most of the slop is in the torque shaft splines which fit “snugger” with a shorter tube. One day I’ll invent an adjustable length torque shaft. 😎

[Gravythe clown]

I shortened both the riser tube and the long tube each by 3 or 5mm (can’t remember exactly, but it wasn’t much). That did help a lot.
the gear mesh was originally pretty good when I got it. I’m used the paper method like setting pinion to main gear mesh. Not real scientific I know. But the biggest slop was in the TT not sitting properly into the umbrella gears inset. The trick was to get it to set but still have some room to “grow”.
when I cut the riser tube I want to say I started at 3mm then grinded on it until I was happy. It didn’t take much after the cut. But the riser was harder because gravity pulls it down out of the upper and sits completely in the lower.
the long tube I just grinded on until It felt locked in. That was easier as I could set the TT depth on the riser transfer gear and slide it in to test fit. It took a couple times of the “old in and out” to get it. And from what I remember I got really close to my 3mm mark I had made on the tube.

by the by D I have a couple of the shims left if you need them. I came across them the other day.

this is another great reason for me why to stick to 500 - 600 size. Not a lot of all this crazy gear maintenance with Trex 500-600’s
Gravy

[PawPaw]

I have some shims as well if you need them. Sounds like Gravy did a good job setting the shaft depths on that Apache. Not an easy task and still keep good tail rotor gearbox-to-tail fin geometry. One of these days I will source the material they use for those torque shafts and make longer ones for my scale helis.

[DCORSAIR]

I have some shims as well if you need them. Sounds like Gravy did a good job setting the shaft depths on that Apache. Not an easy task and still keep good tail rotor gearbox-to-tail fin geometry. One of these days I will source the material they use for those torque shafts and make longer ones for my scale helis.

Ok guys, I might have to get those shims from you one of these days when I need them, I really think the problem is the aluminum torque tube splines versus the metal gears, I see black residue everytime I pull one out, I think that's the biggest issue for slop, the aluminum torque tube is wearing faster than the metal gears. I'm watching mine closely to make sure I catch it in time, be nice to see an aluminum torque tube but with all metal splines on each end.

[PawPaw]

That’s exactly it. Most of the tail slop is those splines’ fit inside the bevel gears. I’m trying something new on this UH-60…I usually cover the holes on the elbow box with aluminum tape after packing the gears with stiff grease but this time I filled the gears with the white lithium. I found that it will flow through the hollow gears and keep the shaft splines coated. Will post the results after I run a few packs on the test stand.