generator mounting orientation ?

[brutus1955]

we started a new forum focused on micro cogeneration
and a topic came up where a guy took a 10kwatt 1800rpm
genhead and mounted it vertically so he could drive it with
a vertical shaft engine that he had,

the question came up as to whether or not the brgs could hold up any reasonable time mounted in this orientation.

certainly motors can be mounted in either way, but i would expect that maybe you need angular contact brg on the bottom to support the weight of the rotor which in this case probably weighs in at around 75lbs.

it seems to be working fine for this guy, but there has been some decenting opinion amoungst the members.

so whats the scoop fella's, i figured if anyone would know maybe i would find out here. if its ok to mount that way it opens the doors to the use of other prime movers and the making of a more compact unit for many folks. if however this is a problem maybe the brgs should be changed for the angular contact type or are deep groove brgs enough?

btw, the new forum is

http://www.microcogen.info

in case anyone is here is interested in this sort of thing.

thanks guys

bob g

 

[electricpete]

I would say it's a hit or miss proposition.

As you say, it can turn into slight overload on one bearing. If machine initially designed to have half weight of rotor in radial direction on two bearings horizontal and you turn it on it's side, you probably have full weight of rotor on one bearing in axial diretion. Since axial load capability of a deep groove bearing is less than radial, this is more than doubling of load. Most likely it's not a problem as long as bearing doens't overheat. You could calculate the change in theoretical fatigue life using bearing tables pretty easily.

I suspect a bigger problem is the beairng that becomes unloaded and susceptible to skidding. It can also overheat and my guess it would have a shorter life than the loaded bearing. Especially if it is a 2-pole machine.

There is also question of lubrication. Typical grease cavity arrangement is slightly different for vertical motor than horizontal.

All of above factors are deviations from ideal, but probably not show stoppers. Perhaps reduction if bearing life by a factor of 2 or 5. Keep an eye on the bearings (housing temperature and vibration) and if reliability is critical, plan for proactive bearing changeout after a year of running or something like that. Just my swag.

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[ScottyUK]

Vertical shaft motors (almost) always incorporate a thrust element, either as a dedicated thrust bearing or in the form of a tapered roller or angular contact bearing. Those that don't have a thrust element rely on the one in the load. I'd be sceptical of what is being proposed, but if the bearing housing is able to constrain bearing movement sufficiently for it to act as a thrust element then maybe you can get away with for a while at least.


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If we learn from our mistakes I'm getting a great education!

 

[edison123]

For 10 KW, 1800 RPM, the ball bearing should take the axial load. I have seen motors up to 100 HP, 3000 RPM being hung from a ball bearing at the top with a roller bearing acting as the guide bearing at the bottom.

If you're developing a line of vertical generators, it would be sensible to talk to SKF, Timken, FAG people.

Muthu

http://www.edison.co.in