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HelicopterRobbe Cuatro - Millennium - Nova - Dyna-X › Milli 2 Sprague question
09-07-2003 07:03 AM  14 years agoPost 1
Blair

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Republic of Canuckistan

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Hi Guys,

I've been having a problem all year with my governor not locking in on my Milli II.

Two different motors, governors, sensors and servos.

Finally I had the heli go in when it felt like I lost collective.

Upon doing an autopsy on the machine I found the one way sprague bearing was cooked.
It had less then 20 flights since being rebuilt and lubed with red oil
(ATF).

The red oil is now a black gummy mess. It's obviousley been slipping and getting hot. I suspect that this slipping was
the reason for the loss of collective (or rotor speed).

This also might explain my engine surging as the load came and went.

The only problem with this theory is that when I test the one way unit in my hand it works fine.

Has anyone ever had one of these fail? Has anyone even cooked one off like this before?

In 7 years of heli's I"ve never had one go bad or a problem manifest like
this.

What do you guys think?

Blair

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09-07-2003 10:48 AM  14 years agoPost 2
Al Magaloff

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12,199 Posts- Enough Time Wasted. See Ya!

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Blair, I don't have a Robbe, but I have had two one ways give up. They both felt and worked fine in hand, but let go under power. I replaced both to "solve" the problem. One of mine slipped in the hub, probably due to not enough press fit. I think this is one of those areas that could use some improving on all the big block combos.

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09-07-2003 11:22 AM  14 years agoPost 3
Andi G

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Switzerland

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Hi,

hmm, the robbe one way is pretty bulletproof. This might be a problem with the center hub (S4610) and not with the sprague bearing (S4448) itself... if you can, check the diameter of the inner part on your and another robbe heli!

It could be some weird reaction between the red oil and the stuff that was in there before too, but I don't think so. This bearing even runs without putting in grease. Had that on my Nova for the first 10 liters or so, then (when I had to change the S4615) I put some blue robbe oil for metal in and had no problems with it so far.

Andi

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09-07-2003 12:51 PM  14 years agoPost 4
Futurac

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Belgium , Europe

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Cooked

Blair

there are 2 things to check

1- in the main hub,4607, there is a stainless steel sleeve, which site very tight inside, and it has 2 small teeth, stucked in the holes of 4607.
if you dont close properly the 4608, and there will be a bt of load, it can come a little up, and start turning in 4607.
2- if there is any dust/sand, inside the hub, indeed the 4610 can turn inside. another thing i saw is a guy openning very quick the motor power, and it cicking this structure, so it can create a possibility for 4610 turn inside the 4448.

i can tell i didnt see more then 2 cases in 10 years...

Alex (Formerly Known as RCMarket )

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09-07-2003 02:22 PM  14 years agoPost 5
Al Magaloff

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Andi, you are right, oil/grease does not lube this thing. It is a mistake to call it a bearing. It has no "bearing" function at all. On the contrary, when the mainshaft is spinning inside this, the rollers are not touching the mainshaft, therefore no "lube" is required here. We lightly oil this so as to facilitate the rollers movement back toward the mainshaft. At a bearing supply store, this would be known as a "Torrington Roller Clutch".

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HelicopterRobbe Cuatro - Millennium - Nova - Dyna-X › Milli 2 Sprague question
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