What the Cr*p! cracking frames when plowing?

[Pruittx2]

My SnoWay will rise up on it's own as you push into a pile,, I have made 7-8' high piles, in the McD's lot I plow,, I also have the Down Pressure feature, that will push the blade down hydraulically and relieve all the weight on the front suspension there by scraping the plowed surface cleaner then just the weight of the plow itself. No problems here.

 

[Joey D]

Boy that crack in the first photo post #1 is way too close to those 'Timbrens' that were talked about.. The frames were made to load at the tortion x-member... Not up front there at the BUMP STOPS..

The frame see's no load at the t bar cross member, it's all at the area where the lower control arms attach to the frame.

 

[3500GMC]

Just plain and simple too much abuse on the frame horns up front. 'Stacking' the 'Timbrens', crap roads cold temps all that 'stuff'..

It's a good guide on *what not to do* to a good truck...

 

[figment]

It's probably the same as with the 6.5. you only hear of the bad.

The gussets would help distribute the stress farther out, (stress from the weight of the plow). The apex would be at or behind the wheel. A fish plate would be better in my opinion but not as easy.

I see similar stress with bale decks on trucks, they break the frame behind the cab at the front deck mount. Welded a few frames up in that area.

I completely agree. I'm convinced fish plating is the only way to go when modifying a truck to handle loads that could or can stress the frame in any way. Don't think that the engineers at the big three factored in all these things the frames would be as heavy as the heavy spec semi's. They build them as lite as possible and as cheap as possible. The dump trucks where I work all have fish plates where the stress is the greatest when dumping a loaded box, and extend a couple feet on either side of the hydrolic rams and in front of the hinge points at the back, from the 1 ton's to the hiway plow rigs, the fish plates are on both inside and outside of the frame, right to the front of the cab. Sure it's a lot of expense but the boss says it's all good in the end. In his words "I would rather pay a mechanic and welder to be bored than see them over worked from doing repairs."

 

[racedaymechanic]

The way I fixed it was to sell the GD snow plow and move 800 miles south, worked like a charm

 

[3500GMC]

^^ I like it.

 

[DieselSlug]

I wouldnt mind that one bit. But the rest of the family is here, and at 23 and in college it just inst feasable.

 

[SnowDrift]

I completely agree. I'm convinced fish plating is the only way to go when modifying a truck to handle loads that could or can stress the frame in any way. Don't think that the engineers at the big three factored in all these things the frames would be as heavy as the heavy spec semi's. They build them as lite as possible and as cheap as possible. The dump trucks where I work all have fish plates where the stress is the greatest when dumping a loaded box, and extend a couple feet on either side of the hydrolic rams and in front of the hinge points at the back, from the 1 ton's to the hiway plow rigs, the fish plates are on both inside and outside of the frame, right to the front of the cab. Sure it's a lot of expense but the boss says it's all good in the end. In his words "I would rather pay a mechanic and welder to be bored than see them over worked from doing repairs."

In their defense, I guess, they can't really design for every possible scenario. The number of breaks vs. the number without breaks is tiny and since we're human, we can all find a way to break something, given enough time and creativity to do so.

Speaking on your "fish plates," though, the situation your describing concerns me if I understand what you're saying. It sounds as if you're saying the load from the cylinders is vertical and the fish plates are vertical also, on the frame web. Is this correct? A picture would be good.

The reason I bring this up is because the fix for these frames, we're seeing earlier in this thread, isn't an efficient one if the only thing happening is fish plating the sides of the frame (the web). Heavy lateral loads might bring about a need for this type of plating, but the loads described here are vertical. This requires straps on the top and bottom (the flange, essentially). Ideally, the ends are cut off at an angle and there are no sharp edges, so a stress riser isn't created from transitioning from a large cross section to a small one, suddenly.

 

[RayMich]

It's probably the same as with the 6.5. you only hear of the bad.

The gussets would help distribute the stress farther out, (stress from the weight of the plow). The apex would be at or behind the wheel. A fish platewould be better in my opinion but not as easy.

I see similar stress with bale decks on trucks, they break the frame behind the cab at the front deck mount. Welded a few frames up in that area.

I completely agree. I'm convinced fish plating is the only way to go when modifying a truck to handle loads that could or can stress the frame in any way. Don't think that the engineers at the big three factored in all these things the frames would be as heavy as the heavy spec semi's. They build them as lite as possible and as cheap as possible. The dump trucks where I work all have fish plates where the stress is the greatest when dumping a loaded box, and extend a couple feet on either side of the hydrolic rams and in front of the hinge points at the back, from the 1 ton's to the hiway plow rigs, the fish plates are on both inside and outside of the frame, right to the front of the cab. Sure it's a lot of expense but the boss says it's all good in the end. In his words "I would rather pay a mechanic and welder to be bored than see them over worked from doing repairs."

Sorry for being ignorant, but what is a FISH PLATE, and how does it reinforce the frame? :???:

Any pictures?

Thanks.

 

[racedaymechanic]

I have been operating and fixing heavy equipment and trucks most of my life, I for the life of me dont know what fish plate is, I know and say fish mouth it can be a gusset cut at 90 degrees, or a chamfer ground for welding Ect. But fish plate? Long John Silvers Special??

 

[NVW]

LOL, must be a term not everyone uses.

It's a plate, usually the depth of the frame that can run any length required. It can be on one or both sides of the frame. If it is cut at 90* at the ends I don't weld the ends, only the top and bottom. If the end is cut at 45* I will weld the ends. The reason for this is it creates a stress riser if it is welded perpendicular to the frame and will crack at the vertical weld. Most frame breaks occur at a crossmember or or a mounting bracket.

I hope this helps.

 

[SnowDrift]

LOL, must be a term not everyone uses.

It's a plate, usually the depth of the frame that can run any length required. It can be on one or both sides of the frame. If it is cut at 90* at the ends I don't weld the ends, only the top and bottom. If the end is cut at 45* I will weld the ends. The reason for this is it creates a stress riser if it is welded perpendicular to the frame and will crack at the vertical weld. Most frame breaks occur at a crossmember or or a mounting bracket.

I hope this helps.

Yeah, good explanation. To take this one step further, a fish plate is, indeed, the portion placed on the web of the member being modified. For a channel, the web is the portion of material separating the flanges. For beam, it's the same function. Beam strength is, generally, a function of the flange mass and the distances to the mass at the most extreme fibers of the material. This is the reason that anytime you see a structural beam or channel, you'll notice the flanges are thick in proportion to the web material. The reason is that the web material only has to resist the shear forces through the center plane. This is the reason you've seen access holes and such that are usually toward the center of the web - there's not much happening at this point and the shear is at or near zero.

Leo welding the ends of the fish plate only when angled is wise. Otherwise, he has to determine the shear forces at the point where the transition is made if it's vertical. If the shear is very high, then drops suddenly, a crack and/or break can occur. This isn't a simple task when we're talking about dynamic loads. Ideally, if a fish plate has to be used, it looks like this: >< where the ends taper up and down toward the flanges and the center is the narrowest place (assuming the flanges are horizontal).

Sometimes a fish plate is the only way to do the work due to the physical space requirements. But, as I mentioned earlier, it's not an efficient way to connect members. The best strength/weight ratio will be had by putting the straps at the flanges, like I mentioned. Judging by the photos I've seen, I think this would be entirely possible with the frames we're looking at.

I'll see if I can dig up some photos of an example from industry.

 

[SnowDrift]

The one photo shows this machine in its raised position. You'll see the cylinder on each side was used to lift this whole assembly into position. Another photo shows it in the down position. The challenging part was that the cylinder had to lift it from near the center of the frame mechanism, pivoting at the front. There was a tremendous amount of force on the frame beam portion being lifted. The stress was too high on this standard beam at the contact point for the cylinder, but it didn't require a heavier beam to accomplish the job, much like the truck frames are adequate, but might just need help in some areas for a specialized job.

To add strength to the beam, I added a strap to the top and bottom of the flanges at the place on the beam where the stress was highest. I've outlined each end of the strap and you may be able to see in the photo that it tapers from nearly the width of the flange at the high stress point, down to near nothing at the ends - and the ends are rounded out with no sharp edges. Note that I had plenty of space available, so I chose the more effective method of adding beam strength by increasing the flange cross sections and not the web. This same method is true if splicing beam or frame sections together.

This assembly that moves weighs in a little over 20,000 lbs. (10 tons) to give a perspective.

 

[RayMich]

Are the fish plates those black brackets that look like 'X' inside a black square on your pictures?

 

[ak diesel driver]

no they are on the top flange of the beam. You can see them if you look carefully. middle pic is the best

 

[racedaymechanic]

No Its This

 

[SnowDrift]

No Its This
View attachment 30731

Ours don't smell, though.:thumbsup:

What is shown in the middle photo is a strap. I didn't use any fish plates on this machine. There was one on the top of the top flange and one on the bottom of the bottom flange at the same location, as AK mentioned.

I think the black piece you're talking about, Ray, is (if you're talking about the part that has one on front and one on back) a bracket I made to hold the screen in place. The large square box looking part is a vibrating screen and it sits on steel springs. Gravity is the only thing that holds it down, so it would roll off when folded down into the transport position, like what is shown in the first photo.

 

[btfarm]

Those cylinders look mighty darn small to be lifting that structure. 2.5"-3" bore at 3000 psi?
I assume that is some sort of mobile crusher/separator rig.

 

[RayMich]

no they are on the top flange of the beam. You can see them if you look carefully. middle pic is the best

Oh! OK, I see it now.

Thanks.

 

[SnowDrift]

Those cylinders look mighty darn small to be lifting that structure. 2.5"-3" bore at 3000 psi?
I assume that is some sort of mobile crusher/separator rig.

They operate at around 2500 psi. They worked perfectly and are still in use today.:thumbsup: