Roban Airwolf 800 build

[mastrg]

That is exactly where I had put it. Was very strange lifted off nicely into a hover, very little input for it stay still,2 to 3 minutes in just leaned to the right would not correct so I could save it. wasn't up high enough to auto. I am not seeing any sites that carry the replacement parts to rebuild except the mast, That thing snapped in two. Well I got my work cut out for me. One good thing is I was testing out of the fuselage, so that is still intact. Good luck with yours, Gary

[Andy01]

Bugger

At least it did not wreck the fuselage. I don't think I have heard of a main shaft snapping in two before - that is a first.

Hope you figure out what caused it. Having a failure like that is bad, but if you don't know what caused it, you will just be waiting for the next one.

Colin

[Russell Harding]

Vibration is a likely cause. Right roll of death.

If you were hovering ungoverned, it probably hit a more resonant frequency after a few minutes.

[mastrg]

Yes, it must of been a vibe issue. Will rebuild take my time, maybe hook up an oscilloscope to check for vibrations. It was pretty smooth before lifting off. Guess I need to figure out a set up to mount it to for spool up and lift off but still keep from hitting the ground. I think of something while waiting for replacement parts. I used the 3M tape for mounting the microbeast, must need to isolate the plate with some Dynomat also to further isolate it. Well I refuse to let this beat me down. Back to turning the big tools need more financing. Gary

[Andy01]

Get a Skookum 720 - it has a vibration log built in

Colin

[treotraveler]

Originally Posted by mastrg

That is exactly where I had put it. Was very strange lifted off nicely into a hover, very little input for it stay still,2 to 3 minutes in just leaned to the right would not correct so I could save it. wasn't up high enough to auto. I am not seeing any sites that carry the replacement parts to rebuild except the mast, That thing snapped in two. Well I got my work cut out for me. One good thing is I was testing out of the fuselage, so that is still intact. Good luck with yours, Gary

It's good the fuse wasn't attached to the mechanics. As you may know, that carbon plate at the rear of the mechanics is not a solid mount. It attaches to the mechanics with two tabs on each side that fits into slots on the side frames.

It will tend to float, and vibrate with shaking anything you have mounted to it. I would suggest that you mod the plate for solid mount, or make a new plate and bolt it to the side frames. or attach the fbl controller to another area of the mechanics....

[muscleflex]

Any photos of the damage?

[mastrg]

Only picture is the image of the one I see over and over in my sleep. I am guessing that with the main shaft snapping like it did. As soon as the blade touched the ground, The shaft broke and both blades and head assembly cartwheeled across the yard. I keep finding parts and linkages in the yard, still missing the top plate bearing and a swash to bell crank linkage. The main shaft broke right at the hole that secures the hub assembly. One blade is broken just before the root and I can see the wooden substrate in it. Oh well when I get all the parts, I can truly say that I built this. Then I will get her back in the air. Yes , I see what you mean with that plate. I think with some reinforcement to it for mounting and some Dynamat, I can isolate it from any resonance. Hopefully before winter sets in, Cause I can't do cold. Gary

[muscleflex]

any updates? i can't seem to find any other build threads for this heli

[ssmith512]

Originally Posted by muscleflex

any updates? i can't seem to find any other build threads for this heli

German site. Decent amount of pics and info........................

http://www.rc-heli.de/board/showthread.php?t=233850

[mastrg]

I am still searching for replacement parts, located the main shaft, tail boom and torque tube. Saw a complete mechanics set up, but it is actually for a 700, the side frames would need to changed out. At 800 dollars a bit costly. Going through the everything I found that the main shaft bearings have a lot of slop. Of course these data breaches have me mired down waiting for a replacement bank card again, third time in 4 years I am definitely changing out the button head screws to allen head type. Going to source new bearings through VXB for a little better quality bearings. Still not finding main blades that don't require changing the head, probably change it as well. This helicopter seems to be a 700 that was stretched to a 800 and not everything was upgraded. I will get there... Gary

[ssmith512]

See this info regarding the mainshaft bearings posted on scalerchelis.com..................

Re: RCAerodyne Super Scale AS350 - 700 Size
Postby cquinby » Mon Aug 25, 2014 10:03 am

I just added some info that I have been meaning to put out there. The info is in regards to the main shaft bearings for all Compactor mechanics.

PLEASE PAY SPECIAL ATTENTION TO THE BELOW INFO

Info on Main Shaft Bearings

Please note that the bearing for the main shaft are not your garden variety Radial Bearings that we are used to. Roban did not use a thrust bearing under the upper bearing dome to deal with the weight load of the helicopter like Vario does. Instead, they went with Angular Contact bearings which are designed for both a radial and axial load without the need for a thrust bearing under the upper plate. The only problem with using these bearings is that if you don't pre-load them properly you will get both axial and radial play in the main shaft. If you notice this do not assume your bearings are bad, you will need to shim under the gears on the main shaft to properly pre-load the bearings. These bearings should provide long service without issue as long as they are loaded. Also note that AC bearings are very fragile when removing the main shaft, they can and often will separate because you will be pulling the shaft in the opposite direction of the pre-load which will cause the races to separate. If this happens your best to just buy a new bearing.

The bearing number is 71901AC and can be found at VXB but prepare to crap your pants at $50+ a bearing. Boca was around $400 last time I checked and it was not truly the correct bearing.
http://www.vxb.com/page/bearings/PROD/Kit12986 (these have ceramic balls and I am not convinced they are worth the money)

I did a little research and found that these bearings are common in the bicycle word for wheel hubs. Rest assured, you can get them for much less: http://www.bikehubstore.com/product-p/bb71901.htm

DO NOT BUY GOBLIN MAIN SHAFT BEARINGS AS A REPLACEMENT they are radial bearing and not AC. This is because the goblin is much lighter than a 18lb scaler and can perform normally with just radial bearings.
Chris

[Andy01]

Gary

I have absolutely no idea about compatibility, but is it worth while looking at whether you could retrofit a Goblin 700 mechanics into this ?

Look on eastcoasthelis.com (the US Vario site) - Joe sells Goblin mechanics and a tail drive adapter for less than $800. I bought my own bits and built the Goblin 770 mechanics to go into my EC-145 for about $350, and I got the tail drive from Joe for about $250 I think.

I don't know if the doghouse on your Airwolf is wide enough for Goblin (all of the dimensions are available on Joe's site), but if so, it may be a good option because everything is readily available and they are pretty solid.

Also, for info, I have been running standard radial bearings in both my 19lb Long Ranger, and a 19lb Seahawk for a few years now without any problems at all. I am not challenging the advice above as it may well be applicable to the Roban helis, but I don't think it is a universal rule of thumb for all heavy scale helis. My Long Ranger has old Heim (like 20 year old) mechanics that were built for scale helis, and it has radial bearings. My EC-145 (4x 820mm blades, probably 25-30lbs ? when finished) will run standard Goblin radial bearings so we shall see how they go

Colin

[mastrg]

Hey, Colin the only thing I see about the bearings is the compactor doesn't have a top bearing retainer. I looked at Joe's offerings and they look like it will indeed fit. I need to contact him and see what the mechanics actually include, looking at the pictures and reading the descriptions. Mechanics means to me everything except the electronics and motor. They would definitely clear issue with the elevator and aileron bellcranks and linkage interfering with each other, might have been my problem from the start. Well let me get this ball rolling. Thank, Gary

[Andy01]

Gary

The mechanics I think Joe refers to (the "complete" kit) is a stock Goblin 700/770 "mechanics", which is the base plate, servo frame, shafts, gears, motor mount etc, and the custom built tail drive adapter to turn a standard Goblin belt drive into a shaft drive. Pretty much what you see in the photos from memory. It does not include linkage rods, ball ends, head etc.

There is two versions of the tail drive adapter - one for low boom helis (Huey, Jet Ranger, probably Bell 222 etc) and one for high boom helis (EC-145, BO-105 etc).

I just bought the separate Goblin parts (not from Joe) as per the Goblin manual, and bought that high boom tail adapter from Joe.

Note that it does not include the CF side frames, battery mount, gyro mount Rx mount etc etc. I did not need or want that because I deliberately wanted to mount the mechanics up in the doghouse, so I made my own mounts etc for the Goblin base plate.

The big advantage of the Goblin setup over many is that the height in minimal allowing it to fit in the doghouse where the mechanics on real helis fits.

Colin

[mastrg]

Colin, I appreciate the info you have given me. Just looking at how those mechanics look, I see the main shaft having better support. The servo lay out will get rid of those bell cranks and extra linkages. I am sure with the entire kit I can come up with a workable solution. Should really stiffen up everything, and a firmer platform for the microbeast. Gary

[muscleflex]

Does AeroDyne (in the USA) not have the full spare parts for this?

[mastrg]

Well, I just checked their website and only saw the main shaft and a blade grip. But I am leaning to the goblin mechanics from east coast vario. I kind of like their idea of direct to swash servos. It will fix the alignment issue with the aileron and elevator servos. All the other bits and pieces are here just haven't started the rebuild as of yet.It is going to be a long cold winter. Plus my PS3 won't leave me alone. Wish I could get my simulator to work on it. I switched the microbeast over to my blade 450 3D to check it out, it didn't get damaged in my crash, in fact no problems with any of the electronics . I will get back on it soon. Gary

[mastrg]

Well I probably need to change the name rebuild. Replacement parts are starting to come in . Trust me when all is said and done, it will be a hybrid. I used the Align 800 upgrade assembly, I had lay out the old parts next to it, didn't recall it being that long. Just could not use the control rod, because the tail servo is in a different position. I also am trying to address main shaft upper bearing support or lack of with the SAB main servo mount. I mounted it to the original top plate, swapped in the KDE main shaft bearing support to double the bearings on the main shaft. I kept the bearings in the top plate and motor plate for a total of 4 bearings. Once every thing was together I machined the servo mount to clear the motor.




. I have fixed the broken shaft so I could get some measurements for the replacement. Put it back in to check for any problems, and I found out I could just get the original shaft. It fits in place with no binds spins freely, I think better then before. I am hoping that RCA shipping calculation is a mistake, $17.00 for USPS . I need to make a call. The new servo mount gets rid of the bellcranks and long linkages, I will make the original servo a receiver mount. Cheers Gary

[heli143]

Gary
Much respect to you for all your efforts.

Will be cool to see your project up and running.