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Wheel Trouble, ...down to 5 good wheels?
mars_armer
post Mar 14 2006, 12:29 AM
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I hate to be the bearer of bad news, but I just heard that there is a serious problem with Spirit's right front drive actuator after yestersol's drive. (This is the actuator that had high currents in the past and led to the backward-driving strategy.) It will take awhile to evaluate the situation, but early speculation is grim.

In a worst-case scenario, they can still drag the bum wheel along, but don't expect another summit view.

Best-case scenario would be a rock or debris jammed in the wheel.

This is a heads-up, sorry I can't really give more info at this time. I still thought you all would like to know.
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Guest_Myran_*
post Mar 14 2006, 12:44 AM
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Thank you for the heads up mars_armer.
With winter approaching which would mean lower temperatures, something might have jammed, but just as you say, lets hope its just a splinter of rock that can be wiggled loose.
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DFinfrock
post Mar 14 2006, 01:20 AM
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QUOTE (mars_armer @ Mar 14 2006, 12:29 AM) *
It will take awhile to evaluate the situation, but early speculation is grim.


The problem is, they can't spend a month trouble-shooting like they did with Oppy at Olympia. Spirit has to make progress toward McCool Hill, and that winter haven. sad.gif

David
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Guest_Sunspot_*
post Mar 14 2006, 01:27 AM
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You mean the wheel will no longer turn at all anymore?
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Shaka
post Mar 14 2006, 01:31 AM
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QUOTE (mars_armer @ Mar 13 2006, 02:29 PM) *
I hate to be the bearer of bad news,

daaaaaaaaaaammmmmmmmm sad.gif Thanx, Mars. I'd shoot you but I'm too depressed.
Finger crossing time, Guys! You know it has to happen, but still...


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mars_armer
post Mar 14 2006, 01:44 AM
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QUOTE (Sunspot @ Mar 13 2006, 05:27 PM) *
You mean the wheel will no longer turn at all anymore?

That's right, it stalled. So far the data is limited, so I may be jumping to conclusions. But based on what I've heard, the most likely interpretation is a failed motor, meaning the right front wheel would be steerable but wouldn't turn.
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Jeff7
post Mar 14 2006, 03:28 AM
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Yeah, let's really just hope that it's just a rock stuck somewhere. I think something like that happened before.
Either way, they know how to drive the thing in 5-wheel mode, which is good. So spin-round, get to safe ground, then analyze the thing thoroughly.
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Guest_BruceMoomaw_*
post Mar 14 2006, 04:13 AM
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Do you mean that the wheel won't turn even if its motor drive is disengaged, or just that the motor has failed?
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Shaka
post Mar 14 2006, 05:15 AM
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QUOTE (BruceMoomaw @ Mar 13 2006, 06:13 PM) *
Do you mean that the wheel won't turn even if its motor drive is disengaged, or just that the motor has failed?

Do we have six clutches on this thing? Can we disengage the motor and free-wheel? huh.gif


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Guest_BruceMoomaw_*
post Mar 14 2006, 05:17 AM
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Under ordinary circumstances that is possible. In fact, it's what they did when they had the earlier problem with high friction in one of the wheel drives, until they managed to redistribute the lubrication to get the motor working properly again.
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CosmicRocker
post Mar 14 2006, 07:08 AM
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Oh, no. So that is one reason why Spirit has moved so little recently. It would seem to be an appropriate time to pray to the engineers. It's not likely to be caused by a rock lodged in the wheel, since Spirit has been travelling over a fairly hard surface recently, and the few available hazcams show no suggestion that debris is in the wheel. It is curious though, that there are so few recent hazcams available if there is an issue with that wheel...3 pairs from sol 774, 1 pair from 776, and nothing else so far. Is that due to the MRO/MOI communication? I thought that would be finished by now.

But yes, that seems to be the $64,000 question. Can it still free-wheel as it once did, or is it locked? All I can tell from the images available so far is that Spirit was driving backwards on sol 774 and it left differently appearing left/right tracks. At some point it had turned around 180 degrees, and then it turned back and was in a somewhat different orientatation/location by sol 776.

Even if the wheel is shot, they should be able to drag it to safer ground, but it may take some learning along the way.


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djellison
post Mar 14 2006, 08:25 AM
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QUOTE (CosmicRocker @ Mar 14 2006, 07:08 AM) *
Oh, no. So that is one reason why Spirit has moved so little recently.


No - read the first post - this is a brand new thing - literally yestersol.

The comparatively little movement recently has been because of the DSN conflict between Spirit and MRO so all commands for Spirit have had to go up via UHF which has a very long lead time - it's like super-restricted sols.

Tosol looks like diag.
QUOTE
780 p0781.03 2 0 0 2 0 4 navcam_1x1_az_324_3_bpp
780 p0981.03 2 0 0 2 0 4 navcam_1x1_az_324_3_bpp
780 p1213.00 2 0 0 2 0 4 ultimate_front_hazcam_3_bpp_pri15
780 p1242.01 1 1 0 0 0 2 front_haz_front_right_wheel_subframe_pri_17
780 p1313.02 2 0 0 2 0 4 rear_haz_ultimate_3bpp_pri15
780 p2138.04 2 0 0 2 1 5 pancam_right_wheel_L27
780 p2138.04 2 0 0 2 1 5 pancam_right_wheel_L27
780 p2600.07 2 2 0 0 2 6 pancam_tau
780 p2630.03 56 2 0 0 2 60 pancam_saw_skysurvey_L4578R2478
781 p1585.00 4 0 4 0 0 8 navcam_cloud_4x1_dwnsmp_RVRAz_calstart

Doug
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Bill Harris
post Mar 14 2006, 08:34 AM
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Oh well, stuff happens. We're all a lot creakier than we were 30-40 years ago.

My suspicion would be that this is a geartrain failure. I forget the exact reduction ratio, but there many gears and bearings between the motor and the wheel and there has been a failure along the way. Remember, we are many hours past the design service life.

Spirit needs to get to an interesting north-facing site. She may be a 3-legged dog, but we still love her...

--Bill


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edstrick
post Mar 14 2006, 10:37 AM
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I note that both from Husband hill and from the drive to and around home plate, the driving on the north McCool "flats" and the lower flank of the hill look mostly pretty easy.... likely sand traps are rare and high-density large cobble areas are scarce. Some of that "diagonal" stripe of lighter and grayer colored terrain on McCool are pretty rubbly and cobbly, but they're not in the drive to get onto the hillslope.
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Marz
post Mar 14 2006, 03:43 PM
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Poor Spirit, just as she regains the lead in milage, she hits another bump in the road.

I suppose there is a plan to return to Homeplate in spring, so I expect the driving around McCool will be very conservative. Maybe if we're lucky, some of the Homeplate unit will be found along the east slopes of McCool.

I was half hoping we could get some closer images of the Chaos terrain that was next on the adjenda, but now I worry it's a rockbed too far.
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