Roban AH-1W Cobra 700 Size Scale Helicopter

[PawPaw]

No...gears are all straight cut. I’m only seeing a difference in the side plate open hole locations. I was trying to orient my support arms in relation to yours when I noticed the difference. Obviously, the tail boom dictates how these arms must mount on the frame to still slide inside so I figured your setup worked. Probably a good thing I haven’t installed them yet as I’m thinking I should disassemble the entire tail tube assembly to add some grease to the 2 internal shaft support bushings. I decided against the lube at first thinking grease would eventually soften the rubber & assembled the tube dry. Now I’m thinking shoulda used silicone grease. Whatcha think?

[sfcfury]

Dang... the tail tube assembly came completed as well? I just used a silicone spray... definitely made it easier to get them down the tube and overall shouldn't damage the rubber bushings. I don't think I would put any type of grease on them.

[DCORSAIR]

I don't think your supposed to grease those bearings either, guess a guy could put just a drop of oil before you slide them in, I just sprayed some WD-40 down my boom and the rubber slid right in place, did you guys remember to offset them so the drive shaft is supported at different measurements and not equal distance from each other??

[PawPaw]

No, I assembled it myself. I installed each bearing 9-1/2” from each end which gives the shaft support in 4 places...roughly 10” spacing. However, those support bearings are free to migrate inside the tube with just a friction fit so gotta believe the engineers allowed for any vibration in the design. Thanks for telling me what I wanted to hear, guys.....didn’t want to take it apart again!

[PawPaw]

How do you interpret this? Set up my Demon 3X FBL programming & it’s 90% finished, except for gyro tuning, etc. I’d rather set a tail rotor blade pitch value with a gauge than the “two ball link turns” method....but in the real world what did y’all do? Thanks!

[sfcfury]

Sorry... I've never used that gyro... the beastx just has you set left and right limits, and the proper gyro sensor direction.

[DCORSAIR]

Yeah, using only Microbeast myself, never set one of those up, two turns on the ball link from neutral?

Pawpaw, so on your bearings, you went 9 1/2 on each end? Its better to do like 9 1/2 on one end and then put the other bearing either farther out or in, not equal distance, I know it sounds strange but it's better to have the bearings different distances apart, I wouldn't take it back apart though, it may work just fine like it is, try it first. There is a theory why you don't do equal distance but I'm not going to go into that.

[PawPaw]

Harmonics? Didn’t think about that. Hopefully the rubber will dampen everything. Got my Scorpion 560Kv today & discovered the bolt mounting pattern will not match the Roban plate for 4 bolts. It will match 2, but the motor’s pattern has the other 2 holes closer to center at the 3 and 9 o’clock positions. Looks like a diamond shape. I checked the website and sure enough, you can see that pattern in the picture if you look closely. Can’t elongate the plate holes either....just not enough “meat” there. Has anybody seen this before?

[DCORSAIR]

Harmonics? Didn’t think about that. Hopefully the rubber will dampen everything. Got my Scorpion 560Kv today & discovered the bolt mounting pattern will not match the Roban plate for 4 bolts. It will match 2, but the motor’s pattern has the other 2 holes closer to center at the 3 and 9 o’clock positions. Looks like a diamond shape. I checked the website and sure enough, you can see that pattern in the picture if you look closely. Can’t elongate the plate holes either....just not enough “meat” there. Has anybody seen this before?

Yep, some motors come with both bolt patterns 25mm/30mm, kind of universal I guess, but I have seen guys using the Scorpion motors on the Roban models, don't know how they are doing that.

[DCORSAIR]

If you need another motor to try and dont mind used??? I will send you an Align 750mx 530KV, I bought it used and never tried it, you will need to order a new shaft though, which comes with new bearings to, the shaft on it is to short for these Roban belt drive units, I will send it to you for free if this will help you out and you could send that Scorpion back if this Align motor will work for you??

[sfcfury]

Yes the bolt pattern on my scorpion was the same... so I ran with two bolts, (I mean that's all I've ever had on my 500 size)... I only did a couple hover flights with it on the test bed, but the bolts didn't come loose at all. That's when I found out you can have the belt tension to tight! So it had to be torn down and get that gear on the vertical tail boom drive shaft replaced. That's when I saw all these tiny upgrades here and there... that motor mount etc. So as I started getting the lil parts coming in, I saw the tengu motor, and you can select a long or short shaft when you order it. (i also ordered a longer shaft for the scorpion- but it got here 3 weeks after the tengu motor came in!)

[RCjetdude]

Definitely following this thread as the Cobra is another of my favorites. Looking good so far!

[PawPaw]

Thanks again, guys. After studying it for awhile I made peace with 2 bolts: The belt tension adjustment bolts maintain center-to-center distance while the 2 motor bolts are loaded mainly in compression. Figure any sheer on the bolts from rotation would be very small.
Please clarify too tight? I have my belt adjusted with about 1/4” deflection when pressed in midpoint between pulleys. Kinda feels “firm” but not solid.

[DCORSAIR]

Thanks again, guys. After studying it for awhile I made peace with 2 bolts: The belt tension adjustment bolts maintain center-to-center distance while the 2 motor bolts are loaded mainly in compression. Figure any sheer on the bolts from rotation would be very small.
Please clarify too tight? I have my belt adjusted with about 1/4” deflection when pressed in midpoint between pulleys. Kinda feels “firm” but not solid.

Good question, I have mine tight, just a little slack when I twist it, thats on my Magnum PI version and on my AH-6 it is really tight, you can play music on it, it was that way when I bought it and I think its too tight, so now that I see how my new one is, I am going to loosen that other one up a little, you don't want to loose and not to tight, kind of a hard decision what is right, I say snug and leave it, I don't want to loose because mine has 5 blades to pull.

[sfcfury]

I think I originally had my about how tight as DC is describing on his AH6... so much I probably could barely put any twist on the belt; but I don't know the tail mechanics setup on the AH6 800 size... but that amount tension lead to the problem. This go around I have it so that when I squeeze the belt from the middle (middle being from motor pulley to big gear) I can get about a 1/2 in of push... and about a quarter twist in the belt. I had it a little bit looser than that at first, and that actually gave a lil slop in the tail mechanics as well.

[PawPaw]

Anybody using Futaba with a CC Talon ESC? It arrived today & I read that I must reverse the throttle direction in the Futaba for the Talon. Will that affect my 3 swashplate servos in collective as well?

[sfcfury]

Shouldn't affect the swash plate... I just looked at the talon card, so yea it says reverse it on the transmitter for futaba.... Pitch slider is what affects the swashplate going up and down...

[sfcfury]

So I remembered I had ordered these crank arms from microhelis.de and it can be built up kinda as tall as you needed, and set for left or right... and just so happens that the servo arm itself was a touch longer! So that's my fix for my tail pushrod!

[PawPaw]

Never mind....answer is yes. Pretty simple to reverse the 3 servos in the FBL programming so all is well.

[PawPaw]

Sorry, sfc....didn’t see your answer after my question! I guess I need to order those crank arms also, then. Figure mine will need ‘em too.