Vintage polo bikes rescued!

the whole single forged one peice thing is good for strength in comparison to something thats machined but 1 peice cranks are not strong at all and generally bend so the cranks aren't in line. I used to regularly bend them on my BMX when I was about 12 and I wasn't that fat! I suppose though if your going for shorter junoir cranks these will be alot stronger than standard length BMX cranks if they are made with the same diameters and stuff.

Likewise, used them for years on BMX and they always broke. You need to consider that there's no chainring bolt either, just a forged peg coming out from the crank which fits (loosely) into the chainring. Lot's of rocking so if you're running these bikes fixed it'll be a pain in the ass.

Surely if the bikes are running a near 1x1 gearing, on grass too, there is not going to be anywhere near the same amount of pressure exerted through the cranks.

If this is the case I think the cheap one piece cranks would be worth a shot. Welding the chain ring to the crank arm is a 2 min job.