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My latest project: Jacking Plates

Re: My latest project

I would agree with Grant. When adding these plates, you are only making the pinch weld stronger, much stronger! If it came a time and you wanted to take them off, then you could leave as is or plug weld the holes you drilled in the pinch weld. It would be easier to plug weld the holes than grind off the welds if you had welded them on.
 
Re: My latest project

Grant 302 said:
The only compromise to the seam would be when you take it off. Then I wouldn't jack or support directly under the hole. These don't go anywhere near where I'd do that anyway.

I was thinking in terms of the bending strength of the runner itself, which the pinch weld is an integral part of if I'm not mistaken. The pinch weld looks to me like it would provide a significant amount of the vertical bending resistance of the runner, which keeps the car from sagging in the middle. If you drill holes in it, aren't you compromising its bending strength at that location? If you're drilling holes at or near the CG location, then (if I remember my structural mechanics correctly) you're drilling them at the location in the runner that is under the greatest amount of bending load.


That's why I'd be more inclined to weld them at that location. In doing that, you're at the very least not compromising the vertical bending resistance of the runner, and may even be improving it.
 

Grant 302

basic and well known psychic
Re: My latest project

kcbrown said:
I was thinking in term of the bending strength of the runner itself, which the pinch weld is an integral part of if I'm not mistaken. The pinch weld looks to me like it would provide a significant amount of the vertical bending resistance of the runner, which keeps the car from sagging in the middle. If you drill holes in it, aren't you compromising its bending strength at that location? If you're drilling holes at or near the CG location, then (if I remember my structural mechanics correctly) you're drilling them at the location in the runner that is under the greatest amount of load.


That's why I'd be more inclined to weld them at that location. In doing that, you're at the very least not compromising the vertical bending resistance of the runner, and may even be improving it.

I believe you're overestimating the impact of two 5/16" holes in the pinch weld to the overall strength of the outboard frame rail. Putting a couple holes in a connection that's spot welded together isn't a big deal. Most of the strength comes from the 'tube' or 'box'. The pinch weld just holds the sections of the box together and is a convenient place to put jacking loads on the front and back ends since it keeps the loads off the 'tube', and why it doesn't matter if it gets a little crushed there. Just don't drill out any of the individual spot welds. While this plate is installed, the clamping on the pinch section should actually make the tube a bit stronger, akin to the strength of seam welding at that location.

Ironically, the only real bending loads in the center would be created by choosing the center of the rail as a jacking point and be opposite of the 'sag' you mention. The whole point of this jacking pad is to keep the weld from crushing and distribute the jacking load to the rest of the frame rail so it doesn't crush. Personally, I think welding on any part of the frame tube section would be a mistake and weaken the tube structure for torsional strength. A strip of weld to the tube would create some localized stress risers and that could lead to longitudinal cracks which actually would compromise the torsional strength.
 
Re: My latest project

Grant 302 said:
I believe you're overestimating the impact of two 5/16" holes in the pinch weld to the overall strength of the outboard frame rail. Putting a couple holes in a connection that's spot welded together isn't a big deal. Most of the strength comes from the 'tube' or 'box'. The pinch weld just holds the sections of the box together and is a convenient place to put jacking loads on the front and back ends since it keeps the loads off the 'tube', and why it doesn't matter if it gets a little crushed there. Just don't drill out any of the individual spot welds. While this plate is installed, the clamping on the pinch section should actually make the tube a bit stronger, akin to the strength of seam welding at that location.

Ah, okay. My mistake, then. I was attributing more structural strength to the pinch weld than is apparently there.

Though I'm not sure that the clamping forces are going to be nearly high enough to add any real strength to the pinch section...


Ironically, the only real bending loads in the center would be created by choosing the center of the rail as a jacking point and be opposite of the 'sag' you mention. The whole point of this jacking pad is to keep the weld from crushing and distribute the jacking load to the rest of the frame rail so it doesn't crush. Personally, I think welding on any part of the frame tube section would be a mistake and weaken the tube structure for torsional strength. A strip of weld to the tube would create some localized stress risers and that could lead to longitudinal cracks which actually would compromise the torsional strength.

I thought of that, and I agree. It's why I was thinking that spot welding the pad in place would be the proper approach. I suppose there might be other possible attachment methods that could be used, too, e.g. adhesives, if one remains concerned about the effects of drilling a couple of holes in the pinch weld.
 

Grant 302

basic and well known psychic
Re: My latest project

kcbrown said:
Ah, okay. My mistake, then. I was attributing more structural strength to the pinch weld than is apparently there.

Though I'm not sure that the clamping forces are going to be nearly high enough to add any real strength to the pinch section...

That's why I said 'a bit'. Fairly certain it's not weaker. It's probably similar adding two spot welds in the seam. Not a significant increase, but 'better'.

kcbrown said:
I thought of that, and I agree. It's why I was thinking that spot welding the pad in place would be the proper approach. I suppose there might be other possible attachment methods that could be used, too, e.g. adhesives, if one remains concerned about the effects of drilling a couple of holes in the pinch weld.
Installed per Mike's instructions, I think adhesives or the spot welds to the pinch wouldn't be better. Adhesives would be trouble to remove if you wanted to take the plate off. Tack welds to the pinch could work okay if the plate is loaded/seated like Mike has it in his directions. But to me, that's the same effort as needing or wanting to plug the holes when the plate comes off. I'd rather have the bolts, and I think Mike has this pretty well thought out.
 
Re: My latest project

Nice! I like how you stuck the decal to the door. I stuck a vinyl stripe on the lower black trim and the finish is very rough. Vinyl does not stick to it very well.
 
Re: My latest project

06mach1 said:
Nice! I like how you stuck the decal to the door. I stuck a vinyl stripe on the lower black trim and the finish is very rough. Vinyl does not stick to it very well.
Thanks Mike. Very happy with your product. Yea they don't seem to stick to the plastic painted parts very well either. I had some Ford blue ovals on the front clip, but first time through the car wash they were gone!
 
3,945
3,999
Re: My latest project

OOOHHH OOHH I have to throw in a gratuitous plug for my website......

http://www.blacksheep-1.com/jackplates.html
 

TymeSlayer

Tramps like us, Baby we were born to run...
3,755
2,625
Exp. Type
HPDE
Exp. Level
3-5 Years
Brighton, Colorado
Re: My latest project

Just an update.

Been using these jack plates for quite some tyme now without issue. They work as advertised and make jacking the car up much easier now. Certainly a worthwhile investment. I do lose a bit of paint on these the more I use them but it's all mostly out-of-sight cosmetics and no big deal.

2012%20Boss%20302%20Mustang%20909_zpsxzvsdu8t.jpg

And yeah, I need to better locate my location sticker!
 
Re: My latest project

Yes, the paint takes a beating between the jack and the road debris from the front tires flying at them. Maybe a coating of bed liner on the bottom would be the way to go.
 
Re: My latest project

Flyboygsxr said:
Are these still available?

Starting another batch of five sets this week. Will be at least a month before they are ready to ship though. Let me know if you want a set.
 
1,022
97
Exp. Type
HPDE
Exp. Level
10-20 Years
Texas
Re: My latest project

Just a thought, but have you thought of including the decals i.e. lift here, or something like that with the kit? Just a thought

Adam
 

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