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Front wheel on Mars rover stops
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Front wheel on Mars rover stops
On Sun, 19 Mar 2006 10:13:14 +0000 (UTC), "SJP"
wrote: http://news.bbc.co.uk/1/hi/sci/tech/4821294.stm they done really well to last as long as they have |
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Front wheel on Mars rover stops
In article , Clive
wrote: On Sun, 19 Mar 2006 10:13:14 +0000 (UTC), "SJP" wrote: http://news.bbc.co.uk/1/hi/sci/tech/4821294.stm they done really well to last as long as they have Just when you need a KwikFit you can never find one! |
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Front wheel on Mars rover stops
"SJP" wrote in message ... http://news.bbc.co.uk/1/hi/sci/tech/4821294.stm Have to admit I am surprised they used brushed motors - surely it would be better to go with motors with only 1 moving part and no consumables?! Scott |
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Front wheel on Mars rover stops
"SC" wrote: Have to admit I am surprised they used brushed motors - surely it would be better to go with motors with only 1 moving part and no consumables?! MER had a tight schedule, and had to use off-the-shelf components wherever possible. Whilst brushless-DC motors have been used successfully by many space missions, such a motor has never been operated on the surface of Mars. MER neither had the time or money to develop the first qualified brushless motor for Mars, so they used the heritage of Pathfinder and MPL, both of which used brush motors. Whilst brushless motors are more reliable and have very long lifetimes, they are more complex, requiring extra electronics. Brush motors, in contrast, are lightweight, with simple mechanical commutation, and provide higher power-to-weight ratios. The graphite brushes that MER use tested at over 100 million revs with no failures. |
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Front wheel on Mars rover stops
"Ed Holden" wrote in message ... "SC" wrote: Have to admit I am surprised they used brushed motors - surely it would be better to go with motors with only 1 moving part and no consumables?! MER had a tight schedule, and had to use off-the-shelf components wherever possible. Whilst brushless-DC motors have been used successfully by many space missions, such a motor has never been operated on the surface of Mars. MER neither had the time or money to develop the first qualified brushless motor for Mars, so they used the heritage of Pathfinder and MPL, both of which used brush motors. Whilst brushless motors are more reliable and have very long lifetimes, they are more complex, requiring extra electronics. Brush motors, in contrast, are lightweight, with simple mechanical commutation, and provide higher power-to-weight ratios. The graphite brushes that MER use tested at over 100 million revs with no failures. I'd also suspect that the problem is actually the bearings at the output shaft, rather than the motor itself. This is where the dust will have been gently eroding, and wrking it's way 'in'... Best Wishes |
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Front wheel on Mars rover stops
SC wrote:
Have to admit I am surprised they used brushed motors - surely it would be better to go with motors with only 1 moving part and no consumables?! The parts have survived way, way beyond their design life. Brushless DC drives have a lot more components to go wrong - just not mechanical ones. A brushless drive has THREE moving parts - the rotor and 2 bearings BTW. Steve |
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Front wheel on Mars rover stops
On Mon, 20 Mar 2006 22:55:47 +0000, Steven wrote:
In article , Clive wrote: On Sun, 19 Mar 2006 10:13:14 +0000 (UTC), "SJP" wrote: http://news.bbc.co.uk/1/hi/sci/tech/4821294.stm they done really well to last as long as they have Just when you need a KwikFit you can never find one! yeah dont think the AA or RAC will travel that far either |
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