This question didn't get any takers at rec.running, so I'll post it here in case anyone is interested.
The running deck on my treadmill broke. Dismantling the unit I see that the deck is 3/4" MDF 48" x 27" Thinking that rather than pay 30 bucks for a 4x8 sheet of the stuff that I'll never use for anything else I could construct a replacement deck from the copious amounts of 3/8" plywood and 1/2" plywood I have on hand. I know, the thickness dimension won't be the same, but there is definitely leeway in that. I can adjust the belt tension to compensate for the slight increase in height.
My question/s are such. Is MDF much better for this application, a situation where the deck will encounter someone running on it for an hour or more every other day. That is, is plywood too flexible (too much flex will strain the bearings for the motor)? Is MDF stronger than plywood assuming the dimensions are the same, more durable? What would you do in this situation, just buy the MDF and figure you'll use the rest for something else?
This is a 3 year old treadmill, rather expensive model and cost to have the vendor ship me a replacement board would likely be more than a new 4x8 sheet of MDF.
I already have a prototype using a single 1/2" plywood sheet, it's definitely too flexible to use. So now I'm wondering if laminating it with a 3/8" would stiffen it up enough.