seanreit

My Feedback: (60)

Yup, not only valid test, but right on to my thoughts. I have never said it to anyone's face, but on the failed servo arms, I have always felt like someone bust be bumping them while in transit, or while turned on, or some factor that is not "normal".

furloughed ual

My Feedback: (31)

Usually that seems to be the case.....How may times have we heard "the radio quit"..... ever notice it's always the same guys having all the problems....

With regards to the servo arms, if they get "cross threaded" on the spline during installation, your dead....I recently bought a plane that had Dubro HD arms made for JR installed on a Hitec....a wonder the plane didnt crash....took about 3 lbs of pull to strip the splines....I truly believe many or most of the problems/failures we see are user induced in some way or another....not always the case, but usually IMHO.....

Tom Antlfinger

My Feedback: (24)

The reason Scott Benedix, SWB, Inc.(one of our club members) arms does not offer 1/16" holes in his arms anymore is simple.....much like the nasty stuff Tam is going thru with his pipe collapse deal and possible law suit threat, Scott was spooked by a couple of Giant Scale pinheads who threatened to sue him when they had a clevis pin failure using his arms with 1/16" holes rather than 4-40 taps.....he did a run of about 100 or so of those couple of years ago.....

This pin failure may have been real on those vibrating 40% birds, but probably not a problem on our jets.....BV has switched over to H9 metal arms on the UltraBandit flaps, but cautions that the pins have to be precision fit into the arms which he offers as pair from BVM with the new UB's or as an upgrade on older ones......this AD came out after David Shulman stripped one or two JR 215's on one of the airshow UB's.....

I much prefer the SWB locking arms over the H9 versions.....My machinist buddy, Paul Jacques, up in Oshkosh, has milled/machined a couple of SWB 1 1/4" arms for those of us locally that fly UB's and precisely drilled holes that are a perfect no-slop fit....then we keep them lubricated with axle grease and some teflon powder......should last forever......I am also converting my JR 215 elevator UB/P-180 arms to SWB with 4-40 ball links......that is first plane I have really thought it might be necessary due to weight just under 50 lbs wet, high-G yanks and banks, and 200+ speeds.....all my other BVM jets have done fine for years with the 215's.......

In the future, Scott may come out with an arm for 1/16" clevis pin, but with a Delron insert to protect from vibration......but it is on the backburner right now, since his 4-40 arms sell like hotcakes.......lots of jet and prop guys still think they are the best of breed, and he still is a bit gun shy as these, win-the-lottery-type-lawsuit pinheads are always lurking......

Tom

ddennison

My Feedback: (15)

HI Harley,

I would agree. I have stripped 4 JR 215 arms on my Kingcat rudders. This occured prior to the crow setting and I had a few instances where the rudders swiped the grass on flaring - stripped both rudders on two separate occasions. This has never been a problem in flight and I also use these arms on my Hornet elev servos.


Dave

furloughed ual

My Feedback: (31)

anyone got a spare JR output shaft and a spare 215 arm to do a test on? Just curious how the JR compares to the Hitec and Dubro's I tested....

Vacman

My Feedback: (14)

Girls,
Deiter and I have stripped more plastic arms off the servo splines than I care to remember! My personal policy is that if I'm using a high output digital servo with the metal output spline, I'm going to use the metal SWB or HD JR metal arm with TWO 2/56 clamping screws!
Plastic arms mounted to plastic output shafts are OK, but plastic arms on a metal output shaft is a set up for stripping the arm! Ask me how well I know this (I have way too many examples)
In regards to the SWBs and the threaded holes, they're terrific. I merely re-taylor the linkage to use the HD ball link anyway (way better and solid, over the clevis).
LKL

Vacman

My Feedback: (14)

Another thing we're not considering here is the fact that we can and do get flutter, especially when busting 200 mph. It may not be a lot of flutter, but just a tad will ruin the splines. Also, it's way to easy to confuse the Hitec plastic arms for the JR plastic arms. Grasshopper must make double sure everything is properly identified.
FWIW

LKL

Harley Condra

My Feedback: (4)

Food for thought, and another way of looking at it.........................
If you build a $10,000 jet, what percentage of the cost of the entire jet is a handfull of aluminum servo arms?

Not enough to sweat.

Using a BVM KingCat as an example, it only costs another $54.00 to use one per flight control surface and one for the nosegear steering.
That is 1/2 of one percent of the entire cost of the jet. Why go through the hassle of stripping an arm, and the worst case possibility of losing the whole jet when you can avoid it for another $54.00?
Makes good sense to me.
(The $54.00 cost is assumed, using using the JetPower servo arm I mentioned in post 16 of this thread.)




Harley Condra
BVM REP
JetCat REP

seanreit

My Feedback: (60)

Harley, your dollars make sense, to me it's not a dollar issue, if you buy 10 Dubro JR gold metal horns, only 4 of them will fit your servo "just right". I guarantee this, and have many examples here of them that aren't right.

Send me your address and I will send you 3 or 4 of them to prove it. There appears to be inconsistency here, and I've never had that with the HD nylon ones.

ddennison

My Feedback: (15)

This is an interesting topic. I had a long talk with Scott (SWB) a few years ago regarding this issue. At that time I was setting up my 40% Cardens and found that all of the Hangar 9 arms were variable with respect to the spline-arm alignment. The SWB arms however are actually referenced when they punch the spline so they are within a degree or so of the arm. The Hangar nine arms always seemed to be a crap shoot from perfect to off by 20 degrees. Fortunately when using them in jets the deflections are much smaller and as long as you can get them centered the "subtrim" required is not too bad (in my experience anyway). Just my two cents...I use either the JR215 or the SWB for everything.

Dave

Harley Condra

My Feedback: (4)

Sean,
I think you must mean Hangar 9 gold metal arms..... not DuBro.

I know about the inconsistency of the Hangar 9 arms....that's why I have started using the Jetpower arms. They fit and the price is right.
Thanks for the offer, but I don't need any more that don't fit.
Why don't I send you some of mine that don't fit.....they must have come from the same batch as yours.


Harley Condra
BVM REP
JetCat REP

seanreit

My Feedback: (60)

I did get your PM and I will certainly look you up when I get down there, I want to see these jetpower ones, and you're right I must be talking about the Hanger 9 ones.

Harley Condra

My Feedback: (4)

Sean,
I will be working in the BVM tent for set up and the whole show. come on bye.
I will show them to you.


Harley Condra
BVM REP
JetCat REP

Tom Antlfinger

My Feedback: (24)

Dave, you are 100% right about the radial accuracy of Scott's arms.....how he got there is a long story with threats of patent infringement from the guy that was vendoring the arms for H9, as well as JR who initially refused to accept the fact that their metal output gear on the 8611/8711 series had poor quality control compared to what was on the 2721 and 8411's......I have seen the output gears Scott has measured right out of the box on new 8611's back when they first came out......no question, significant caliber differences......Scott's 8411 metal arms worked on some, but not on others, so JR said just stick with the 215 arms which worked fine, except when they stripped, mainly when banging a surface while transporting or in the pits.....

Scott is a master builder and flyer of Carden 40% stuff himself and could not stand the random orientation of the splines to the arms on all the metal arms available in the early 2000's, so he set out to make the best......

JR initially wouldn't hear of it.....they offered no locking arms for quite a while after the 8611's came out.....

Scott purchased the best broach money could buy and then used precision techniques to cut the splines, and then came up with the locking arm concept that now is used by others.....he thought about patenting his design elements, but way to expensive for a 1 man machine shop......so now we have all kinds of copies.....

I still use only Scott's....designed and manufacured by a local U.S. businessman......and IMO, still the best......

Like Harley pointed out, the cost is infinitessimal compared to his example $10,000.00 jet, or more like $18,000.00 bucks for the UB.....


Tom

mr_matt

My Feedback: (10)

I agree 100% SWB arms are the best, Nelson's a close second for a smaller wheel type arm