At the risk of seeming stupid ...

I'm a rock only Adirondack climber thinking about trying ice climbing. I've watched others ice climb and it seems a lot of ice chunks often fall down on the belayer, that looks potentially dangerous to me. Does anyone use (or tried) belaying with a motorcycle helmet ?Although heavy, motorcycle helmets are way tougher than climbing helmets, have full face shields, are totally windproof, are warm and look safer that climbing helmets. Does any ever use them ?

You might look stupid but I wouldn't think you seem stupid.

mostly its about putting the belayer in the correct place so they don't get bombed. and yes carrying around the weight of a motorcycle helmet would be stupid. 

You will see people ice climbing with full face shields sometimes.

But falling ice isn’t usually such a big concern that it requires a modified helmet. An attentive belayer can be positioned safely and/or get out of the way of smaller chunks. If the falling ice is big enough that the belayer can’t avoid it, the thickness of your helmet is the least of your problems.

I have climbed "fresh" rock climbs where a face shield seemed prudent

Daniel Kay wrote: You will see people ice climbing with full face shields sometimes.

But falling ice isn’t usually such a big concern that it requires a modified helmet. An attentive belayer can be positioned safely and/or get out of the way of smaller chunks. If the falling ice is big enough that the belayer can’t avoid it, the thickness of your helmet is the least of your problems.

I've only limited experience "watching" but it seemed there's always a steady stream of small ice chunks coming from "up high", either from the ice axes or just dislodged pieces.. Recent climbing  helmets are ultra light and comfortable, but look like they wouldn't last many "ice hits" to the head". Not  sure how tough full face shields are.

Hey Ian,

Often the belayer finds a stance quite a bit away from the wall if possible, upwards of 15-20'. It's really not as big of an issue as it may seem it would be and I wouldn't bother with a non climbing helmet.

I have used a ski helmet, but pretty much stopped as it was too warm when actually climbing! (except on the coldest days, like 0F and below) I'd think a motorcycle hemet would be even warmer, definitely heavier.

If you plan your belay location and have the ability to move, I find the belayer should not be getting bombed by much. Look at the ground and frequently you can see the debris and the fall area, so avoid those areas. Yes some small stuff does come down but it may be climber technique that needs improvement to keep all the bombs to a minimum size. I am seeing that most "dinner"plates that are knocked down are due to the climber not recognizing that the bulge they are hammering on is not the best for a pick placement and should find a better concave for a pick placement. 

position them out of the way of falling ice. It's expected so why stand under it

I've used Team Wendy helmets (in a different context) and they offer a helmet line for the outdoors (intended for the SAR market mostly). These are legit pieces of dome cover but there are penalties to be paid in weight and cost.  When it comes to safety, don't stop thinking. If your internal voice advocating self-preservation whispers "there might be a better solution", there probably is.  Have fun.