Shear in itself is simple and additive and proportional to cross-sectional area. If we're dealing with pure shear, a bolt in double shear is equivalent to a bolt of twice the cross-sectional area (i.e. 1.4142 times the diameter) in single shear. Where double-shear detailing is easy, it's a good way to double the shear capacity of a fastener which would have been adequate in single shear. Very often we're not dealing with pure shear. In fact, I'd submit that most badly-designed single-shear situations are really badly-designed cantilever situations. They fail not from a too-small fastener shearing off but from it bending plastically and subsequently fatiguing. In such cases the "double-shear" detail may be up to eight times as strong as the "single-shear" detail, depending on the way the fastener is held at its ends. That's actually a very good example. You haven't really improved the overall shear capacity, because you've got two shear situations and you've improved only one of them, but you've made a far, far better cantilever — as long as the short bolt is above or below the main bolt, and not beside it — and that is the main thing you needed to do.
In the case of the coil overs, the failure of the mount or bolts was that the coil overs bottom out and something has to give. By adding axle bump stops it avoids that issue. Sent from my iPhone using The H.A.M.B. mobile app
When a spacer is required in a single shear situation under load, I like to weld the spacer to whatever it's butted to if possible, just to increase strength. It's an easy thing to do, and very effective way to increase strength. Same for shock bolts. If you weld the head of the bolt once it's through the mounting plate, you turn it into a stud, and the setup is strengthened in a single shear situation over just bolted and not secured at the head of the bolt. Welding stops the bolt from being leveraged by the loads imposed on it in single shear.
I'm glad too see this question asked and see that its getting some good replies. I'm in the process of building mounts for my coil-over suspension and I have gone with double shear on my mounts , this front mount will be double shear on bottom that mounts on top of the tube axle and the top mount is a stud so I'm building cups, mock-up in blue, that mount to a upright stanchion that gets welded to the frame and on the top it will be welded to the part of the roll cage that goes from the frame and passes through the fire wall, also it will have extra holes for adjustability of shock hight. My question is my material ? is 3/16" heavy enough? Everything I would see online was 1/8" thickness. I like stuff mounted very well, I tend to use my hot rods and use them I do. The remaining axle mountings are with 4 bar and panhard bar. I also factored in my engine location to help determine my type ,strength, of mounting for the front suspension mounts, mine is a sbc that will be set back..the balancer and pulleys will be right at the axle.. Sent from my SM-T387V using The H.A.M.B. mobile app
The problem associated with items mounted in single shear is when the common load area between the part and the piece holding it is threaded. If the load area is the shank its fine as long as the requirements are correct, if that area is threaded, then the strength becomes the root dia of the thread but includes a fracture point at the base of the thread. Ty-rod can be single shear because the only thread is past the mount/holder, the rest is all shank
RudeStude, The link to calculator below will help you understand your mounting tab design. Material selection is critical as well. 3/16" of cheap A36 50 ksi steel may be required, buy if you go with a higher strength steel, say a 90 ksi A514 steel plate, then perhaps only 1/8" plate is required. Make sure your welding rod / wire matches the grade of steel you are using as well. No sense in spending money on a high strength alloy to stick it on with low strength welds. https://mechanicalc.com/calculators/lifting-lug-analysis/
Most general use welding rods / wire are either 60 or 70 thousand p.s.i. , probably not a strength concern in either case
Talking about thread thickness in single sheer, most suspension bolts will have a much thicker should going through the part ( shock , control arm etc) then the diameter of the threads. something to keep in mind when building stuff, your off the shelf bolts might be the weakest link.
I'd like to see some of these double shear lower shock mounts installed. Anyone got pics they can share?
I have a couple of this type of race car coil over shock mou nts, but they don't work for what I was doing . I guess the idea on these is taking the direct shear 9ff of the bolt. Don't know if that explanation goes along with what I'm thinking ...but I know that there is a reason that all your race car coil over mounts are done that way. Sent from my SM-T387V using The H.A.M.B. mobile app
It actually works by improving the beam strength of the bolt. The fixed sleeve, the moving sleeve, and the sleeve in the coilover eye are all compressed together and together with the bolt itself make up a composite beam. It is a valid instance of preload, and it works on the principle of a post-tensioned beam, in which the bolt performs the function of a structural tendon. Tensioning the bolt makes the entire assembly more rigid than a solid circular beam of the same OD as the sleeves.
Well hell Ned .....just get all technical....no really, I thank you. When I see stuff like that , I guess common sense gives me a idea of its purpose but when it gets too the technical part and the real meat of it .....ya Luckily through all my hot rod building , driving , and racing ventures throughout the years I have had some pretty good friends that could dial me in on the technical side of things . That type of mounting is what I'm doing on the rear coilovers on my build, with the lower mount being adjustable. I will also be doing it on my front coil-over lower mounting tabs. Thanks for the technical "why" part of the purpose of the parts. Terry (aka Rudestude) Translation : Damn Good. Sent from my SM-T387V using The H.A.M.B. mobile app
The problem is the coilovers, buggy springs, which ride as well or better, have double single shear spring connectors, "Shackles" Most of the time going backwards is forward.
That is very true . My reasoning for coil-overs was only because they were new and given to me forfree from a friend also for what I'm building, visually I really like the look of a tube axle , coil-over 4-bar suspension set up , and it fits nicely in the nose of my 50 bullet nose Stude , which is getting a setback, the balancer will be right at the front axle, sbc with tunnel ram , M22 crusher, out to a narrowed Dana 60 with 4.11 ,spool, ford tube ends and racing axles. Suspended on coil-overs and truck arms...and no a gasser want to be its not ... More of the 70's street freak kind of thing..but squatted down on the ground with cut out rear quarters and 29x18.5x15 Thompsons on stealies and in front skinny Thompsons on 15x4 1/2 Americans. Its just going to be my go to town car...after driving it as a stocker for 6years it was time for a change. So the choice for coil - overs had nothing to do with ride or comfort in my case, I just wanted wild ,crazy and different, kind of, hot rod.....if I want to go with smooth and comfort, I'll just drive one of my Cadillacs. Sent from my SM-T387V using The H.A.M.B. mobile app
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