John,

Why would you want to clip on the shoulder belts instead of wrapping them??

 

Hey! A question I think I can answer correctly. Less stretch of the belts and no possibility to slide or move along the bar.

Don

 

Sliding along the tube is easy to control with split collars.

Does this method truly reduce the likelihood of stretch?

I kind of like the idea of clipping the belts in, but I'm not sure I want to introduce a stress riser to the tube. I'm not being the least bit critical, I'm just curious if this is something I want to adapt to my cage.

 

This is one that really makes me happy;

This is a multi-faceted situation, and solution. It is easy to create a solution for the problem that is staring you in the face. It is much harder, and more satisfying, to come up with one solution for many problems at once. This one does that.

One shoulder belt problem is lateral slippage. Geo is dead bang when he says you can solve that with split collars. I was ready to order some before I came up with this solution. Obviously, slippage is eliminated with this mount.

Another problem is slippage of the 3-bar slider. When faced with enough load, the loop of material that you have around the tube WILL slip until it tightens around it. On top of belt elongation and other factors, you just don't want to add any length to the belts. However, you must leave enough slack for the belt loop to orient itself to achieve a straight load path off the tube. This solution eliminates that one too.

There is another phenomenon linked to the previous one. When the belts are slack, they will naturally droop and try to fall under the belt bar. If you do not leave the right amount of slack in that belt loop around the tube, and 3-bar slider falls underneath, when it is pulled tight, it may wedge itself in a downward position and give a false tightness to the belt. I've had this happen; Thinking the belts were tight, when they had actually wedged under the bottom of the tube, only to slip when enough cornering force was created. Kind of a bad feeling, especially when you don't know what just happened. This solution eliminates that too.

Yet another point is that this solution fixs the belts closely together, which is good for ANY belt setup, and particularly helpful for HANS users. 3-4" between belts being the optimal setup.

Using this criteria enters another variable into the mix. When you fix the belts that closely together, they will not be pulling perpendicular to (straight off) the mount tube. This creates a shear force in the material, as the inside edge of the belt will be more taught and stressed more than the outside. Apparently this is not of great concern (up to a point), as Schroth recommends this setup, and even crossing the belts if the length to the body is longer than 18". However, no sense entering loads into the belts that you don't need to. The eye bolt mount always allows a perfectly straight load path no matter the circumstance.

If all of those problems solved were not enough, this arrangement also happens to look extremely sanitary and highly refined. For those not interested in esthetics, you can probably add something to make it look ugly again.

 

I agree;

There is the potential for a more focussed load here. If I had a solitary belt tube with no other bracing between its ends, I'd be more concerned. With the diagonal intersecting it - shortening its unsupported length - I'm less so. Then the only concern is the localized failure of the tube material or welds. If you were really worried, you could sleeve the tube and bolt right through.

 

I was going to ask the same question. My concern with that belt setup is that you are taking a load that is spread out the full 2-3" of the belts and concentrating it at a single point. Did you do the calculations to determine at what G load the bar will fail?

 

John,
I'm not trying to undermine your opinion, but don't you think pros and companies would use this method if it were superior? Simpson seems to know a thing about safety, and I haven't seen them suggest clipping the belts (but maybe they have and I don't know). Also, I might be missing something here, but the belt still must attach to the clip/terminal with a 3-bar slider, doesn't it?

 

Another fantastic Rennlist thread! Please enlighten more.

 

There are always some issues and ther is no perfect way. The clip-in is open on one side and the belts are still using a 3 bar slider in John's pic. I think this is not an advantage VS collars and straps around bar. John has a winner it he uses a bolt in triangle and sewn in belt on the triangle. I do not think bar stress is ever an issue. The overall mass of bar metal is much greater than the tiny 3/8" hook of material on the clip-in holding the belts. To me those are scary and we all just accept them. Also, John's set-up is longer front to back. So you have to make sure there is plenty of clearance to have the eye bolt sticking out say 1.5" and the clip 1.5" and the 3bar slider 1.5" so you need a minimum 4.5-5" from bar to seatback. Sometimes you just do not have the clearance. The FIA HANS guide also has different rules than just the 3-4" generic spread between the belt anchor points. The belt spread distance can be varied based on the distance of the back of the HANS to the harness bar see their chart. It is quite confusing. I Thought of this design but I did not like the idea of those 1.5" posts (eye bolts) sticking me in the back if the seat collapses. I'm just parnoid. Even My back brace posts are at my shoulders not at my spine. You can weld the eye bolts facing up but then the shear on the eye's is wrong since they are designed to be in line with the long axis of the threads. I also question whether you can just weld hardened grade 8 eyebolts without changing their strength property. I was taught not to weld fasteners. My solution was to drill the harness bar and sleeve it, then us AN nut bolts through complete triangles. My was was way too much work unless you are using the 4 shoulder HANS and trying to get the required vertical spread without using 2 harness bars or a special mount. So I would just wrap the harness bar and just use collars and besides it's lighter...no eyebolts, no clip-in's, no weld pool X2 for the passenger side. When I gutted my car nothing I removed was heavy. When I went to empty the trash can I could almost not lift it. All those little things add up.

 

FatbillyBob,

The looks good. What does the rest of the cage look like?

 

I don't want to hijack this thread. I actually posted it here before but I'm not sure how to find it.

 

Ok, thats fine. I'll search it.

 

O.K. I found it https://rennlist.com/forums/2586420-post.html

 

Expect something close to 2,000 give or take 500.

 

This link shows the whole thread: https://rennlist.com/forums/racing-and-drivers-education-forum/238875-cage-critique-welcome.html#post2586420