Hi. I'm trying to design a set of sliprings for transferring power and signals. But they need to be fully submerged in a liquid, possibly an oil or alcohol - I have some freedom in selecting its properties. Can anyone help me to work out how to ensure the contacts will remain connected?
The power is about 200V, 1A. The range of movement is only 180degrees and with a maximum speed on the order of 1 rev/second.
snipped-for-privacy@hotmail.co.uk wrote in news:1167499445.940058.30870 @a3g2000cwd.googlegroups.com:
If you make the liquid mercury then your system will work very well.
Otherwise what sort of life/temperature/cost/whatever tradeoffs matter? By observation whatever cheap electric brushed DC motors use works under water for a short while.
Yes, mercury is the easy way out though, and it isn't very cool these days. Then there's another problem of how to contain it.
Lifetime should be about 100,000 cycles. I did try running a brush motor in oil or water once (can't remember which), and it didn't last long at all, as you say. But that would have arcing which won't occur here.
I'm really w> If you make the liquid mercury then your system will work very well. >
Have you considered magnetic power coupling? It will eliminate 99% of the problems you are dealing with now.
With a rotation range of 180 degrees, the effective solution is a highly flexible 2- 3- or 4- conductor cable wrapped loosely round the axis. If the need is for ultra-high integrity, then a flexible spring strip of stainless or bronze to which the cable is fixed would be much more reliable than any slip rings you are likely to design or source.
Brian Whatcott Altus OK
Hi. Yes I've actually worked out solutions using steel springs or loops of copper wire, but I was hoping to gain some advantages from the sliprings. If it's not possible, that's fine, but I want to be sure before giving up.
To Amossisonca1, yes inductive coupling would be possible too, in fact I have a transformer there anyway which could be modified to serve both purposes. That's an idea I'll still have to consider futher.
Surely predicting metal-to-metal contact in oil lubricated mechanisms is a common engineering problem. But I'm not sure how to find information on this.
Post also to
Some inductive coupling sites
check referencesat end
snipped-for-privacy@hotmail.co.uk wrote in news:1167537586.576966.186920 @i12g2000cwa.googlegroups.com:
As Brian stated, a cable will give you the desired effect.....and life, provided you use the right cable. I have found that the Flex-Life cables from Turck will handle this with no issues. We have an application where cables must rotate 180 while in an environment of coolant, aluminum chips, oil, and other hazards. We have tried many brands of high-flex cables and the Turck last 3x as long. They are oil and abrasion resistant in addition to being very high- flex....and cheaper than the others *with* molded ends at custom lengths. Our normal life for these cables is on average, 600,000 cycles.
Anthony wrote in news:Xns98AA6F21E3ABacziparle3sp835@216.77.188.18:
The 4 or 6 wires in a steering wheel are designed for much longer life, reliability, and so on than this. The mechanism is called a clockspring, and as, as you have all suggested, is a flexible ribbon cable. It will provide in excess of 400 degrees of rotation in each direction. So take a wander down to a scrapyard.
Cheers
Greg Locock
Find a book on lubrication and hydrodynamic bearings. In that application, the question is how to keep the surfaces separated by a film of liquid, and your objective is the opposite, but the same analysis should apply.
Olin Perry Norton
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