X-SPec
YS 91
MPII
9254 on throttle
Throttle Jockey Pro

Have been chasing this problem for a while. On hard climb outs my engine would start pulsing, fairly fast, from making good power, to going to idle (actually sounded like it was trying to quit and then come back to life again a couple of times a second). I'd back off on the climb out and all would be well again. No problems just flying around in FFF, but anytime you asked for some extra umph, I'd get the pulsing. Thought maybe it was due to seasonal changes here in Iowa and that I needed to tweak my mixture or something. I also thought about a cracked bearing, but wasn't having an over-speed problem, just the opposite. That, and I'm no 3D pilot, not even close. Then today I had the forethought to try the hard climb-outs with the governor off. Now I was getting pulsing in the opposite direction, from making good power, to the engine sounding like it was REALLY coming up on the pipe. Then the light bulb finally came on. The Throttle Jockey/9254 was reacting so fast to the bearing slipping that all I would hear was the engine going to idle, then coming back to life again, then shutting down again, etc, etc.

So, now that I had somewhere to look for a problem, I pulled the auto hub bearing. It took some hard looking with a powerful magnifying glass, but there it was, no less than 5 very very small hairline cracks. Like I said, I'm no 3D pilot, and generally don't get to crazy when I'm flying. However after reflecting on this a bit, I do recall twice having bailed out of an auto without having first switched back into normal mode. I remember thinking at the time, "That's really got to stress something..." I did do the Agusto grease mode during the build, and re-greased at the last 'annual'.

I see that on Heliproz's site that p/n 2500-048 has been discontinued and is now superseded by p/n 2500-102. Is this an improved bearing? Or is this one still subject to cracking?

-Mark
.

There, their and they're. It's really that simple.

cracked bearings 'happen' all the time

even the -102 cracks (happened to me already). The grease mod
and making sure the bearing fits the hub well improves the situation
but my hunch is that I'm going to eventually spring for the
new new new improved hub bearing that I see is (or will be soon)
available that uses a totally different design (I'm not sure
if it's the E3 hub or something even newer than that).

Yes get the 2500-120(opps, yes 2500-102) as it is the updated bearing, it is the one included in the EVO90 kits. In my experience it tends to last longer then the former one.

2500-120 or the 2500-102?

Dr. Dan

Been there done that..

#2500-102 is the 'newer' bearing which comes with the EVO90.

Both -048 and -102 seems to crack as easily, now Im using the WC3 hub but havent flown it much lately though.
Reports is saying that the WC3 one should keep up.

/Fredrik
'Hm now I just have to find out where to connect the GV1 sensor to the Jazz80 ESC.

I couldn't find the 120 at Ricks. I have broke 2 bearings in te past and want to keep a few on hand. Whats the part # or the WC3? Is that the 120?

Dr. Dan

Realized last night that the EVO 30 I have sitting on the bench awaiting parts uses the same auto hub bearing as the X-Spec. So........ I'M BACK IN THE AIR! And what a difference! That bearing must have been deteriorating slowly over a long period of time. Slow enough that I didn't notice it from one flight to the next until it really started to slip. Now I have my old X-Spec back. Smooth as ever with excellent pitch authority. Definitely going to be keeping one of those bearings in my spares box.

-Mark

There, their and they're. It's really that simple.

I keep a whole gear stack in my flight box.

Three ball links and two screws to swap it out.

Fix the spare at the house later.

-RCA .......... Making Cuisinarts Fly!!!!!!!

DrDan
There´s no oneway called -120.
The WC3 hub with bearings is #0414-309.

/Fredrik
'Hm now I just have to find out where to connect the GV1 sensor to the Jazz80 ESC.

Yeah, that's what I thought, but a 2500-120 was mentioned earlier in the thread, and I had never heard of it.

Dr. Dan

DrDan,

There is no 2500-120, I meant 2500-102, sorry for the confusion. In my experience they do hold up better an the original. The other option would be to go with the WC3 Hub as MrNoddles indicated. I've been running this hub now for a while now have yet to crack a bearing. Please note that if you go this route you will not need to order the bearing as it is included with the hub.

Well, I took the cracked bearing to work today. I dye-checked it. 8 cracks total - 1 crack for each side of the bearing. So, if you think your bearing isn't cracked, dye-check it the next time you have it out. It may surprise you. I just barely found 5 cracks with the aid of a very good magnifying glass. Would not have found the other 3 without dye checking.

A brief explanation of how the dye-check works
1. Dye is applied to bearing and allowed to dwell (soak) for about 15 minutes.
2. Dye is removed with lint free towel that has been sprayed lightly with a solvent to insure ALL dye is removed.
3. A developer is applied. The developer drys to a powder and pulls any dye that remains in the crack to the surface. Crack appears as red against white powdered background

-Mark

There, their and they're. It's really that simple.

Sorry if I highjack the topic, but has anyone tried the KSJ Auto-hub for the Eagle/Freya series?
It looks like a nice piece of work and they claim they're using a larger one-way bearing.

The lot I got is not a lot, but I thank God a lot for the lot I got!

Mikerobe
Some of us is using the WC3 hub, I guess both hubs pricetags is in the same area, and the WC3 one seems to work.

/Fredrik
'Hm now I just have to find out where to connect the GV1 sensor to the Jazz80 ESC.