Hello, I've just recently designed a part holding rack for someone that will be placed through a furnace, after finishing it they asked for a simple cart to put it on to take it to and from the furnace. The rack is 62 L, 23 H, 31 D. Fully loaded the cart and rack will weight an estimated 1,500 lbs and will rest on 8" casters. Now this is all easy until they ask for a brake, what they'd like is a handbrake on the bar that works in reverse. You must squeeze the handle of the brake to release it allowing the cart to be pushed. If at any time the operator trips/falls/stops paying attention and releases it the cart will stop moving. I considered a spring loaded system but stopping 3/4 of a ton from moving may be too much for my original design. If at possible they also requested the handle be almost like the throttle handle of a push lawn mower. A smaller bar running parallel to the cart handle that would be squeezed to it. Does anyone have suggestions on how to make this, or of a part that already exists? Thank you very much in advance!