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Monday, September 21, 2015

Shoulder belt mount

Time to mount the shoulder belt mount, part # 2180 from Midfifty. I had for a long time taught about how to make the holes in the cab to line up the predrilled and threaded holes in the shoulder mount. Well one night it just hit me, a piece of bent steel wire was the tool I needed.

Just hold the plate in the place you want and take the bent steel wire and let it find the hole on the backside and the front will pinpoint exactly where you should drill the holes. Easy! ;-)

Both sides done, but one thing is for sure. These cabs aren´t exactly symmetrical and the mounts from midfifty needed some massaging in the bench wise to even reach between the posts.

I got some questions if I taught these mount would actually withstand an impact.

I made some simple computation. These plates are hold in place using 6 pcs of  4.75mm Grade 3 screws. These 6 screw has a total cross section area of ((PI*4.75^2)*6)/4=106 mm2.
A lap belt is sufficient to keep a body inside the cab (fairly well), The lap belt is hold in place using two larger bolt with a corresponding cross section area of ((PI*8^2)*2)/4= 100 mm2

This means that the shoulder mount is held in place with 6 screw that has the equal or slightly more strength than the 2 bolts holding a lap belt.

I made on quite large assumption during this simple computation, I assumed that all of the load i transferred in tension thru the 6 bolts while in fact the bolts are more or less there just to keep the plate in place. Most of the load will transfer as a load out to the door and window post, where you will have even more load carrying cross section area.

So my conclusion is that it is safe to say, they will make a huge improvement on the safety of our cabs and seat belts. 

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