Quote:
Originally Posted by Boort
You'd want to distribute the load across multiple cross members. I would not be really concerned about the cross members carrying the weight. Some back of the napkin calculations: The cross member profiles are 1x2" extruded aluminum about 47" long (on my 4th gen) If you weigh 200 lbs and stand in the center of the member it would be expected to deflect a bit more than 1/3" down. (not accounting for any deflection of the side panels that are supporting the ends.)
Each cross member is connected by 2 Stainless Steel 1/4x20 bolts at each end. The shoulder of the profile would take out much of the leverage by the 1/3" deflection caused by the center load. So your 200 lbs on just one member would be focused primarily on the shank and heads of these bolts. Looking up a grade 5 1/4x20 bolt would report a clamping force of 1117lbs over a clamping area of 0.0318 Sq Inches. 200lbs spread evenly across the 4 bolts works out to each bolt supporting ~50lbs + 1/4 the 1 lb weight of the cross member itself.
The next item down is the mounting points on you're 4Runner's roof which I don't have specific details for other than the original rack's load rating of 150 lbs. But that was likely due to all of the fiberglass/GRP in the stock rack rather than the mounting point failure load.
TLDR: you probably don't want to focus all of your weight on just 1 or 2 cross members but otherwise I think the Sherpa rack can take the point load of a 200lb person standing on top.
The Owners and Engineers from
@ SherpaEquipmentCo
are members here and could weigh in with more technical details or point out where my calculations are wrong.
Boort |
Quote:
Originally Posted by Ambient
Thanks for the replies.
I'm thinking I'll have to put down a piece of plywood anyway, so the tripod has something to rest on and I can move around without worrying about my feet too much.
Looks like I'm good to go!
|
Boort you really broke this down quite well!
Through real-world experience, you can stand on just one cross-member. It will absolutely deflect though. I will say if you are planning on taking pictures you'll want to be comfortable and standing on just one bar is not at all comfortable. Building yourself a platform or purchasing a couple of our
Adapt plates or similar style plates that bridge the crossbars and make a platform would be ideal. Youll be able to then put a camping chair or chair of your choosing up there, place your tripod and hang out in comfort! While at King of the Hammers I stood on my adapt plate often taking pictures with my long lens!
