Gearbox Chip Detector

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TFF

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Are they really false positives or do you only respect when it looks like a chea-pet? It’s a count down device. Get a sliver every 500 hours, who cares. Then it shortens to 100; then to 75, then 50. Your choice when to call it on a homebuilt. If you are getting every 10 hours, it’s telling you something. How long can you put up with it is up to you, but at some point it looks like a chea-pet. Unless it’s a sun gear, it’s usually not panic time. It’s note taking time. We would get lights on tailrotor boxes enough to clean them off before certain pilots got in them because they would freak out. The only big box one that counted had just a couple of slivers. Looked inside, three teeth gone. They were just still too big. They needed to grind up some more. Tail gearboxes were from manufacturing trash trapped behind some bearings migrating through trying to escape. Would trash the bearings. No scary flight problems, but they were on the way.
 

TXFlyGuy

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Does the manufacturer recommend a chip detector? If so can they not supply one?

We have frag detectors on the T58's and T55's but they don't show as much as a good magnet in the reservoir.
Perhaps. They normally make hundreds/thousands for Pratt & Whitney and other OEM types. So getting them to make a one-off for us might not work.
 

Deuelly

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Myron, I used to fly for a patrol company. They thought chip detectors would give early warning of problems and save the high cost of major repairs. Detectors were add to all their piston aircraft. After about a year they removed all of the detectors. Frequent false alarms kept the aircraft grounded and they NEVER FOUND ANY PROBLEMS from the detector warnings.
Russell Sherwood
If you were getting that many false alarms they were sized wrong. We run them in some pretty high performance aircraft engines and don't usually see anything till an engine is on it's way out.

Brandon
 

D Hillberg

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Helicopters use them all over , If a bearing goes bad it will warn you.

Fuzz happens as the gear box breaks in. [ A chip light with a high temp and you park it & look]

We'd make our own, drill a passage in a drain plug for stud or screw that runs through a plastic washer and a tube to keep the stud or screw from touching the plug body and the threaded end with another plastic washer under a magnet , last a nut to keep it all together, the threads are long enough to put a wire on the end.
The main item is the space inside between the head and body of the plug where the washer seats. too small a gap and the fuzz wins or a gap too large and the chips don't bridge the gap and you lose.
 

TXFlyGuy

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Helicopters use them all over , If a bearing goes bad it will warn you.

Fuzz happens as the gear box breaks in. [ A chip light with a high temp and you park it & look]

We'd make our own, drill a passage in a drain plug for stud or screw that runs through a plastic washer and a tube to keep the stud or screw from touching the plug body and the threaded end with another plastic washer under a magnet , last a nut to keep it all together, the threads are long enough to put a wire on the end.
The main item is the space inside between the head and body of the plug where the washer seats. too small a gap and the fuzz wins or a gap too large and the chips don't bridge the gap and you lose.
We want the "Goldilocks" gap...not too large, not too small, just right!
 

D Hillberg

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Rotax doesn’t use them on their gearboxes. I’ve a friend with a Jet Ranger that gets false readings regularly. I’d blow that idea off.
Know a few who blew off an indication - Lost gear boxes and wrecked their machines.

Your Jet Ranger friend is looking for an accident (get oil tested for trace metals & fix it):grave:

We used them on all the Jet exec gear boxes / with tele-temps. 4 on each. x 100 AC sold = Cheap insurance
 

Mark Z

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I agree an oil analysis is probably a better indicator. This will determine what and how much material is being generated. Initially there will be metals in a fresh engine.
 

TXFlyGuy

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One off? Your gearbox manufacture makes them or?
The gearbox manufacturer has them available, but he is in New Zealand, under total lock down. We found an OEM company here who makes these for several companies, including Pratt & Whitney. They are looking at making one (1) for us.
 

wsimpso1

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A chip light with a high temp and you park it & look.

We'd make our own, drill a passage in a drain plug for stud or screw that runs through a plastic washer and a tube to keep the stud or screw from touching the plug body and the threaded end with another plastic washer under a magnet , last a nut to keep it all together, the threads are long enough to put a wire on the end.
The main item is the space inside between the head and body of the plug where the washer seats. too small a gap and the fuzz wins or a gap too large and the chips don't bridge the gap and you lose.
Any idea what the right gap is for these guys? Or do we have to develop it? Hmm, I will chat with a recently retired pump and filter geek to see if there is a contamination sample product that could be used to tune this sort of gadget...

In the automatic transmission world, we had all kinds and sizes of metal, with quite a bit of fine iron generated on first run. The electronic group did investigate a chip detector. I that they were inductive devices that were tuned by design and electronics to trigger based upon any one size of chips becoming present significantly above ambient quantities. They did not save us or the customer enough money to bother, so we can not piggy back on an automotive part. I would prefer to know that I have an imminent gearbox failure. Would have been nice to use that, but last I heard, even ZF and Allison do not run them.

Bill
 

TXFlyGuy

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Any idea what the right gap is for these guys? Or do we have to develop it? Hmm, I will chat with a recently retired pump and filter geek to see if there is a contamination sample product that could be used to tune this sort of gadget...

In the automatic transmission world, we had all kinds and sizes of metal, with quite a bit of fine iron generated on first run. The electronic group did investigate a chip detector. I that they were inductive devices that were tuned by design and electronics to trigger based upon any one size of chips becoming present significantly above ambient quantities. They did not save us or the customer enough money to bother, so we can not piggy back on an automotive part. I would prefer to know that I have an imminent gearbox failure. Would have been nice to use that, but last I heard, even ZF and Allison do not run them.

Bill
Typically none of the T-51 gearboxes have chip detectors. The thinking is a high temp warning is sufficient to let you know of impending failure.
 

TFF

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In a plane it will at least glide when there is a problem. Helicopters eat themselves if the spinning stuff stops. No centrifugal force on the blades, they start flailing, chopping you up. That is what happened to that big helicopter in the gulf last year. Main gearbox locked up. I don’t know if he was trying to ditch or trying to make it to a platform, but he was in the air too long. At the regional airline I worked at we had the bull gear on a CT-7 come out of the gearbox. One of the most amazing things I had seen at the time.
 

D Hillberg

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Any idea what the right gap is for these guys? Or do we have to develop it? Hmm, I will chat with a recently retired pump and filter geek to see if there is a contamination sample product that could be used to tune this sort of gadget...

In the automatic transmission world, we had all kinds and sizes of metal, with quite a bit of fine iron generated on first run. The electronic group did investigate a chip detector. I that they were inductive devices that were tuned by design and electronics to trigger based upon any one size of chips becoming present significantly above ambient quantities. They did not save us or the customer enough money to bother, so we can not piggy back on an automotive part. I would prefer to know that I have an imminent gearbox failure. Would have been nice to use that, but last I heard, even ZF and Allison do not run them.

Bill
3/32 of an inch to 1/8 to give the fuzz time to grow without causing problems
 

BrianW

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Altus SW Oklahoma
One method for detecting steel chips: find a small rod magnet. cement an insulating sheath; cement a thin iron tube around that.
Secure a push on connector to both the central magnet and the surrounding iron tube.
Iron chips attach to the magnet and when touching the surround electrode, the short circuit can set an alarm..
Not helpful for lead/tin copper etc.
 

Rik-

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San Rafael, California
The gearbox manufacturer has them available, but he is in New Zealand, under total lock down. We found an OEM company here who makes these for several companies, including Pratt & Whitney. They are looking at making one (1) for us.
That’s a bit easier to understand
 

Heliano

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Just a quick reminder: all turboprop engines that I know of (Pt6's, PW's, Honeywell(former Garrett), etc.) have chip detectors in their gearboxes. Do they trigger false alarms? yes, they do. However experience has shown over and over along decades that the benefit of having an early alarm when things are beginning to go bad inside a gearbox compensates everything. And turboprops are constant torque, while piston engines are intermitent torque (torque varies from x to 5x as they rotate, as function of combustion taking place), therefore in principle piston engnes are more critical from the standpoint of mechanical failures.
 

Bill-Higdon

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Just a quick reminder: all turboprop engines that I know of (Pt6's, PW's, Honeywell(former Garrett), etc.) have chip detectors in their gearboxes. Do they trigger false alarms? yes, they do. However experience has shown over and over along decades that the benefit of having an early alarm when things are beginning to go bad inside a gearbox compensates everything. And turboprops are constant torque, while piston engines are intermitent torque (torque varies from x to 5x as they rotate, as function of combustion taking place), therefore in principle piston engnes are more critical from the standpoint of mechanical failures.
All of the Military Helicopters I worked on had them also, yes some false alarms but prevented a lot of crashes, lost equipment & lives.
 
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