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01-14-2006 04:27 AM  13 years ago
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lavarocks

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Rochester, NY

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CSM SL 560 Drift
So I have this CSM SL 560 micro gyro, and it's drifting in the HH mode.

I set it up using the quick setup method a couple times to ensure I didn't make an error (like moving something when I'm not supposed to)

It is a slight drift to the right, and would take maybe 3 clicks of rudder trim to fix

This is the second machine it's been on with this slight drift.

Any ideas?
- chuckyteets
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01-14-2006 04:53 AM  13 years ago
TMoore

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Cookeville, TN

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Too much Quick Trim offset will do it. If it exceeds +/- 10% it will drift. Mine did it. Trim the heli out mechanically, 0 the Quick Trim offset with the PC link and then engage HH.

TM
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01-14-2006 04:56 AM  13 years ago
lavarocks

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Rochester, NY

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I haven't done the quick trim at all yet, would that make a difference with a drift in HH mode?

Edit: It is mechanically trimmed perfectly in Mode 0 (not 'smart lock' mode)

When I engage the heading hold (smart lock), it begins to drift...
- chuckyteets
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01-14-2006 05:28 AM  13 years ago
TMoore

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Is it a V3 or V4 560? Did you link up to the gyro and see if there was anything in the Quick Trim settings?

TM
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01-14-2006 05:35 AM  13 years ago
lavarocks

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I don't have the PC link, the gyro is a loaner.

Is there any way to clear the settings without the interface?

I also have no idea of the version, unless there is a way to tell just by looking at the gyro.

I have no accompanying paperwork. Thanks for tryin' to help me out here
- chuckyteets
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01-14-2006 05:37 AM  13 years ago
TMoore

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Cookeville, TN

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I'm not aware of any way to clear the settings w/o the link. It's probably a V3 unit unless it is very new.

Try using Quick Trim and see if it gets better. YOu can download the instructions from the CSM website.

TM
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01-14-2006 05:40 AM  13 years ago
lavarocks

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Rochester, NY

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Thanks, I'll try the quick trim tomorrow. It's a little tough to hit that switch consitantly and not hit the bookshelf and cabinets in the living room..

This is on an XL Rex..
- chuckyteets
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01-14-2006 05:43 AM  13 years ago
andyp

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New Zealand

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The quick trim is cleared each time you run the quick set up. ie you dont need the interface to clear the quick trim.

Maybe worth while trying the brass plate mounting method.

Andrew
QuickUK Flight Team
Fromeco Regulators and Batteries
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01-14-2006 05:54 AM  13 years ago
lavarocks

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Rochester, NY

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Are there any other settings in there that could be causing it to do this?

Also, brass plate mounting... To make it a stiffer mount? Or does that hit the natural frequency of the vibrations a little better to cancel them out?
- chuckyteets
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01-14-2006 09:24 AM  13 years ago
andyp

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New Zealand

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From the CSM web site:
http://www.rcmodels.org/csm/

NEW: Anti Vibration Mounting System

Designed for the SL720, but can be used for ANY small gyro or sensor (30mm square or under). Ideal for 90 size and petrol powered (gasser) helicopters, it typically reduces vibration effects by a factor of 5, protecting your sensor. This increases the accuracy of the gyro and the usable gyro gain, and also reduces the strain on the tail rotor, lowering power consumption and wear.

The mounting system comes with twelve anti-vibration foam pads; we recommend that you use four to six at a time. Extra foams are available. Please note that the mounting system comes free with the SL720.
Consists of a thin mounting pad, a 30mm square steel plate, and anti-vibration pads

Andrew
QuickUK Flight Team
Fromeco Regulators and Batteries
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01-15-2006 01:01 PM  13 years ago
zoom boy

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N.E. Lincolnshire UK

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Some things need clearing up here.

Quick trim is more for rate mode than anything else, HH it doesnt have much effect at all since the gyro will drive the servo to where ever it needs to be (within the throw limits) to get the required yaw rate, in the case of centre stick, 0 degrees/s

If you do quick setup again it should clear and reset the quicktrim.

Then mechanically set it up, you can do this so that its so close anyway some dont even bother with quicktrim.

Make sure you are doing quicktrim in the hover though, I know one person who always did it on the ground and wondered why the tail never stopped turning.

HH

Now, the thing that could be causing a drift in HH mode could be one of the following.

1, trim
2, subtrim
3, vibration
4, mixing
5, the radios centre stick pulse width

1, centre it
2, centre it (for now)
3, can you see any vibration of the heli????
4, check your radio settings
5, the standard pulse width for futaba and sanwa/airtronics is 1520us, for JR its 1500us.

#5 To see what its set to you need the interface, if its different from the value for your radio brand then it will cause a bias to one side, so change it to match.

Or

You dont need the interface to fix that however, you can actually use a small bit of subtrim to compensate for it, so all the years of "dont use subtrim" forget about them, in some cases you have to, a midstick pulselength mismatch being one of them.
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01-16-2006 12:15 AM  13 years ago
Yug

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UK. Herts

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lavarocks. The dreaded drift strikes again
I had a very similar experience to you - it would start drifting in flight so I would dial it out with a bit of trim. I ended up finding that this was down to 2 things.
Temperature was the main culprit as the Murata gyro element is not temperature compensated. When the heli is sitting on the ground in the sunshine, it warms up. When its time to fly, the gyro will initally be at a higher temperature, and will calibrate accordingly when first switched on. However, after a minute or so into the flight, the gyro will cool down and this results in an electrical offset from the output of the gyro element, and hence you get drift. Bummer. There are 2 things you can do to help minimise this. Land, switch off, switch on to force recalibrate (at running temperature), and get flying. The other thing is to keep it covered when on the ground so as to make sure it is at ambient temperature.
The 2nd problem is the mounting. The 560 is quite sensitive to vibes in the form of gyroscopic precession - the vibes cause it to wobble cyclically which results in drift. The best you can do is mount the gyro on a 30mm x 30mm brass plate, which is itself mounted on 4 feet cut from the normal mounting pad. The brass plate adds mass to the gyro and so reduces its mechanical resonance. The 4 feet tend to minimise the cyclic wobble.
Good luck.
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01-17-2006 04:58 PM  13 years ago
lavarocks

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Rochester, NY

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In response to zoomboy: The radio is a clean slate as far as rudder trims go. It will still drift. The radio pulse length is 1500 (JR) and the software readout matches this. If enough sub-trim is put in to cancel out this drift after it's been initialized it flies okay. If the sub-trim is left in for the next flight, it will start to drift again (it has to be trimmed EVERY initialization). This makes me think it cannot be a pulse width problem.

The helicopter should not be vibrating very much at all, it is a small electric (T-Rex) set up with a high headspeed. I guess that's the next step, though...

In response to Guy Martin: It cannot be temperature, this gyro has flown mostly indoors, and once outdoors. Same problem every time.

So judging by all that's been said, it has to be vibration from poor mounting? I will try to get one of these mounting kits from CSM..

Edit (1-17-06): Where can I get this mounting stuff in the US?
- chuckyteets
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01-17-2006 05:08 PM  13 years ago
Yug

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You could try adding a mix when switching to HH as a temporary fix.
The mounting kit is a 1mm steel plate (could use brass) 30mm x 30mm. The gyro sits on this with thin tape, and the whole thing sits on 4 feet. Just take a normal CSM pad and cut it into 4. Interested to see how you get on.
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01-17-2006 07:01 PM  13 years ago
zoom boy

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It actually could be temperature, where on the heli is it mounted?

If its on the tail, in theory then the rotor downdraft could be cooling it down enough to cause a little drift.
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01-17-2006 07:19 PM  13 years ago
lavarocks

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Rochester, NY

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Eh, it's on the tail, but it doesn't get worse as flying goes on, it's just constant, all the time. I am really doubting its temperature related.

How thick is the foam that comes with these gyros? I'm starting to think now that I have simply not padded it enough.
- chuckyteets
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01-17-2006 08:56 PM  13 years ago
lavarocks

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Rochester, NY

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I just tried it real quick with more layers of foam tape, and a quarter inbetween to act as that plate would. Same exact drift...- chuckyteets
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01-17-2006 10:28 PM  13 years ago
zoom boy

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N.E. Lincolnshire UK

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What you want is about 7x7mm of foam in each corner, those support the brass or alu sheet, then that needs a 1mm or there abouts thick piece of foam, that is what the gyro is mounted to.
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01-17-2006 10:35 PM  13 years ago
lavarocks

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Rochester, NY

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Correct me if I'm wrong, but isn't that style of mounting mainly useful for larger machines with a lot of vibration?

This is a very small machine with very little vibration.
- chuckyteets
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01-17-2006 11:42 PM  13 years ago
Yug

rrMaster

UK. Herts

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Fair point. The added mass of the brass plate reduces the resonance of the gyro. A small electric heli will have much higher frequencies of vibration, so the gyro should be even smoother. hmmmmmmm
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