How Dan Splits an Atom, then fusion back together ;)

[darkfa8]

I recently picked up two Atom 500 airframes. One was a somewhat worn out 500R, the other; a low time carbon version. The 500R came with a flybarless head conversion. I stripped both of them down to parts. Tossed the worn out, broken and trashed parts.

So, this thread will pick up with my experience building one airframe. I've built and worked on well over 30 models since 2005. I realize this model is a 2 year old design, but I'll drop in my 2-cents anyway on the design, construction and eventual flight anyway.

To start my rebuilding I always take used or "ARF" models and take them down to nuts and bolts. I check for and clean off any old thread lock. On used models I soak and re-grease all of the bearings using a Greaser, and essentially build it up as a kit. So, I tore these models down, dumped all the hard parts and bearings into rubbing alcohol (70%) for 48 hours. Then flushed everything with water, dried and then started my sub-assemblies.

I decided to start with the tail since I'm doing some modifications to the frames that I'll get into later. Before I tore everything down I checked the action on all of the moving parts, ball links, etc. to get a feel for any inherent binding. The tail in my opinion was not as smooth and effortless as I thought it could be. Upon reassembly I sanded the inside flats of the plastic "H" piece that attaches to the tail case housing with a long pin so that when onserted to the housing there is little to no resistance. Once the pin was installed (need to wick in some Tri-Flow lube to the shaft's hole), this "H" piece moved freely with no resistance.

I then did the same sort of sanding to the inside edges of the pitch plate actuator arm so it would swing freely once pinned to the "H" piece. Again, I'll wick some Tri-flow oil in at the pivot points. These two bits of sanding made the tail action substantially more smooth. Some might say that if left in stock condition, they'd eventually wear in. That may be, but I'd prefer to have a smooth, bind-free tail at the get-go and be more kind to my tail servo.

I rebuilt the pitch plate, re-greased the bearings and installed the pin screws with a small drop of thick CA glue on the threads. I finished rebuilding the tail grips with lubed bearings. I did notice that they have a marginal amount of play on the hub shaft, but figured it wasn't worth trying to tighten them up since centrifugal forces are just going to cancel it out. I used a small smear of high strength (red) thread lock on the blade grip-to-hub M2.5 screws to insure the grips don't come flying off as a result of a loose screw.

Once reassembled, the tail action was substantially more smooth than it had been. I probably could have further improved on it if I had tapped out the tail pulley gear roll pin and pulled out the tail shaft, chucked it in a drill and polished it. Maybe on the next rebuild

I'll be popping the tail case onto the tail boom soon, but I'll be drilling out the two indentations so the "pinch" screws actually screw into the boom.

The frame reassembly is the next major thing to do, but after I modify it I'll be installing PEM nuts to retain the servos.

More to come and with pictures...

[kevinator9]

Nice write up Dan. I am interested in how the rest goes

[darkfa8]

well, i finished the tail assembly. I had to re-ream the tail push-rod ball links to get as smooth an action as possible. It's much better than stock and will make the tail servo's job a lot easier. One of the used booms I had was already drilled for the retaining screws, so less work for me.

only thing I botched was installing the boom such that the Compass logo is upside down lol ... I debated about leaving it, but instead, for now I covered it with a "Powered by Castle" label

I got all of the PEM nuts installed. This will make servo installation and service so much easier. I have the frame dry assembled and awaiting final alignment on a Enco granite block. I keep the main shaft in the frame to line up the main bearing blocks. I then sequentially tighten all of the screws in a alternating side star pattern starting on the outer edge and moving in and leave the main bearing blocks for last. Once everything is tight and presuming the main shaft falls through the blocks with no resistance, I'll again sequentially remove one screw at a time, apply thread lock and then reinstall.

Once the frame is all done, I'll start on rebuilding the flybarless head. Then it'll be on to installing electronics, setup etc...

[Ah Clem]

"only think I botched was I installed the boom such that the Compass logo is upside down lol ..."

You should have left it, but you would have to fly it inverted all the time...
Or only fly it in the Southern Hemisphere...

[darkfa8]

the labels are removable....

[hoot]

Nice thread Dan.

The granite block is a great tool to have but way overkill for assembly. They are designed for .00001" accuracy. A formica counter top will get you as close as you need. The frames, holes and parts aren't nearly accurate enough to expect the bottom two edges of the frames to be used as a reference greater than a few thousandths at best. Nonetheless it's a good way to do it if you have it (granite).

Basically what you are doing is blueprinting the heli. You'll end up with a better than new machine when you are done. Unfortunately the ground has a way of correcting your meticulous build

Looking forward to some pictures and your impressions.

[darkfa8]

The granite block was less than $30 shipped and I can spare my kitchen counters for food prep

I think I enjoy blueprinting more than flying

[hoot]

Where did you get the block Dan? I may get one myself. They're also great for checking shafts and other precision work and inspection.

[hoot]

Just ordered one from Enco... thanks for the tip.

[darkfa8]

hope you used a coupon code I got 10% off mine

for everyone else's reference:

http://www.use-enco.com/CGI/INSRIT?P...&PARTPG=INLMK3

[Helico-pteron]

Or just go to your local granite counter top store and ask for a scrap piece.

[hoot]

I used a free shipping code.

[alexmit]

A decently thick sheet of glass works nicely in place of granite too. It's also a nice tool for rolling shafts to see if they are bent.

[darkfa8]

My prelim electronics line-up:

cyclic: MKS DS9660A+ (at 6vdc)
tail: MKS DS8910A+ (a 6vdc)
esc: Castle Phoenix ICE 50
bec: Western Robotics Super Mini (need to buy)
gyro: Futaba GY750 (need to wait to buy) or good used BeastX
receiver: Futaba R6202B (need to wait to buy)
motor: stock Compass, 9t pinion
lipos: possibly Flightpower, waiting to buy all new lipos for this season

[Dflyer]

Hi Dan,

Compass recommends using a 60A ESC when you use the 9t pinion, a 40A ESC is sufficiant enough only when you use the 8t pinion. So i think the ICE 50A is just not enough for use with the 9t pinion.

Grtz,
Dirk

[darkfa8]

i intend to run a lower head speed (2400) and FBL and as per Castle Link's projections, the 9t is the correct gear for a 2400 head speed, gives a power out of just over 96%. Of course, once the model flies, I'll be checking the data and adjust my gearing accordingly as needed.

[hoot]

alexmit, That is a good idea too.

Dan,

I got this one. Shipping weight was 70lbs.... but free.
I went for the grade A larger one for the real estate and accuracy not that the grade B wouldn't serve the purpose. I always tend to lean towards upgrading.

640-0422 12"X18" 1MP GRD A GRANITE SURFACE PLATE 1 104.98 $104.98

[darkfa8]

very nice choice!

unfortunately, I don't have the room for such a piece, so I have the smaller, much less expensive B-grade version. It's plenty big for me to setup 700-size frames on and I can easily lift it (~30lbs or so) and store it in a closest when not in use - I live in an apartment, so my work space is limited and multi-purpose.

BTW - the granite block was originally recommended to me by Ben Minor who also uses it to setup frames, engines in motor mounts, check shafts and other tasks requiring a more true flat surface.

[hoot]

Can't beat granite for accuracy and stability.

[hoot]

Dan

Sorry I hijacked but I have to tell you I don't know how they shipped it (granite) and made money. It was at my doorstep today. I almost got a hernia picking it up..