1/2" Carriage Bolt Loading?

tomrscott · Jan 8, 2005

1/2\" Carriage Bolt Loading?

This should be simple for someone out there. I can probably find this somewhere, but off hand don't know where.

My JD790 rear R4 wheels have four 1/2" carriage bolt holes (square holes) for mounting wheel weights. I'm wondering what the load capacity of those carriage bolts are? I'd like to put about 500 lbs of homebrew wheel weights on them, but the JD owners manual doesn't say what the limit is. They say you can mount up to 3 of their cast iron wheel weights per wheel. The tractor manual doesn't say what their weights weigh, but they don't ever really say that the limit is the strength of the wheel or bolts. It may just be how long the bolts they supply are. Could also be an excess of caution over liability issues with as nutty as their lawyers have gotten.

Seems to me, just my mechanical intuition, those bolts ought to handle about 500 pounds each (~2.5 x my weight?). The wheel rim face is 3/8" thick steel. With four bolts, seems like 500 lbs per wheel ought to be safe? /forums/images/graemlins/ooo.gif

bobodu · Jan 8, 2005

Re: 1/2\" Carriage Bolt Loading?

If in doubt...buy grade 8s.. /forums/images/graemlins/grin.gif

ThistleKop · Jan 8, 2005

Re: 1/2\" Carriage Bolt Loading?

If in doubt...buy grade 8s 

Bobodu, They may be grade 8. He did not say what they are. That is a very relevant point. Can be determined by looking at the marking on the head of the bolts.

TK

Soundguy · Jan 8, 2005

Re: 1/2\" Carriage Bolt Loading?

Sure.. just straight load.. it would take quite a bit to have a failure on even a grade 2 bolt. Side loading and shear, and shock loading all effect that. However.. with 4 holes per wheel.. I'd guess you can bolt on as much weight as the tractor can handle with (4) 1/2" carriage bolts. if in doubt.. use grade 5 or 8. I'd guess 4 grade 8 bolts would carry as much weight than a scut tractor axle will be rated for. when you count both rears and even fronts.. etc..

Soundguy

PILOON · Jan 8, 2005

Re: 1/2\" Carriage Bolt Loading?

As far as I know, carriage bolts would not be available in the higher grades, like 8.
Only ones I have ever seen are the hardware store variety mild steel.

On the other hand 4 ea 1/2 bolts can take a lot of wt.

My concern would be the fact that in this application they would be in shear and also they will tend to wander and possibly wear through.

As suggested better to use grade 8 or better regular machine bolts and washers even if you have to get a helper to hold a spanner on the other side.

Probability is that JD have graded special PN's for that application.

My 2 cents.

justforme · Jan 8, 2005

Re: 1/2\" Carriage Bolt Loading?

mcmaster.com

has grade 5 carriage bolts listed on there site

additionally they have 8.8's if you need something in metric

tomrscott · Jan 8, 2005

Re: 1/2\" Carriage Bolt Loading?

I am surprised that carriage bolts are available in grade 5, but that is good to know, thanks!

Another consideration: I would rather the bolts snap than the wheel face get deformed at all if this is going to be pushing it, but I am really having a tough time imagining that it can be a problem. Still, maybe I am better off using cheap carriage bolts. The are surely not better steel than the wheel face, and if something is going to give, they'll shear and I'll know pretty quick. It's not like it is going to be a major catastrophe if a wheel weight starts clattering on two or three bolts cause one or two sheared off.

The weights I am making are out of 3/8" plate, about 20 pounds each, easy enough to handle one at a time.

I got to thinking that I have put my whole 200+ lbs of weight on a single cheap grade 1/4" lag bolt without snapping it. The more I think about it, I think even the lowest grade 1/2" bolts would probably each hold the 500 lbs, with four I am having a hard time getting worried about it.

If the wheel face were thinner material, I might worry about it deforming, but 3/8" plate is pretty stout. I am sure a John Deere wheel is good quality steel.

Soundguy · Jan 9, 2005

Re: 1/2\" Carriage Bolt Loading?

( As far as I know, carriage bolts would not be available in the higher grades, like 8.
)

The specialty fastener store that the GC I work for buys from can get just about any type of bolt.. any grade.. any material... and yes.. we have bought hard carriage bolts.

( this application they would be in shear )

My concern as well.

I think I would find some pipe to cut and use as a bushing or spacer.. and add a few large flat washers to that, and size the weights mount holes for those pipe sections. Either way.. 4 bolts are gonna hold alot of weight.. no matter what grade.

Soundguy

mrcaptainbob · Jan 9, 2005

Re: 1/2\" Carriage Bolt Loading?

I agree with that, Soundguy. Four 1/2" grade 5 bolts would hold a lot. Heck, that's only 125# per! I don't think, however, that these are really in shear and that the chance of the weight hanging from a couple on one side (should two adjacent actually break!) would stand a bigger chance of rim distortion by the time the last two gave way. I don't think any of that would really happen though.

JJT · Jan 9, 2005

Re: 1/2\" Carriage Bolt Loading?

No problems with the bolts and the load. Anybody see a problem with 500#'s per wheel on a JD790? Seems excessive to me. My larger Kubota only has 400#'s per wheel and that's CACL.

JerryG · Jan 9, 2005

Re: 1/2\" Carriage Bolt Loading?

Trying to place all of those weight plate on the wheel with 4 bolts is going to be a hard thing to do. You also have to drill a lot of holes for that many 1/2" bolts. Have you thought about just making a plate that bolts onto the wheel with one bolt for the weights. That way, you can just slip one weight on at a time and not have to try putting the whole stack on 4 bolts at once. Example

tomrscott · Jan 9, 2005

Re: 1/2\" Carriage Bolt Loading?

JerryG,

RE: "...one bolt for the weights"

Yeah I have thought about that. It is similar to what "EZ-Weight" does to use weightlifting weights:

http://www.ezweights.com/install.php

There are tradeoffs both ways. I've got a large drill press, so the hole drilling is not a large concern. I could also use the Plasma Cutter that I am going to cut them out with.

Mounting the plates is indeed going to be somewhat more tricky with four loose bolts, but I've given it some thought and believe I may have an approach that could work. The idea is to control the stack with some long alignment pins to give you some leverage, keeping the bulk of the weight up close to the wheel and not letting it slide away from the wheel. I don't know if I can describe this well enough without pictures, but the idea is this:

1) Park the wheel with two mounting holes up and down and two horizontally aligned, in a diamond pattern.
2) Use two "alignment pins." Two 1/2" hardened shafts, maybe something like 2' long and support them at one end in the two horizontally aligned wheel holes, and at the other end by a brace of some kind, maybe just a couple of 2x4s.
3) Slide the weights on the two pins one or two at a time, over the two pins. Perhaps with a pair of support braces, one at half way and one at the end, gradually building up the stack until you have all plates in place temporarily aligned by the two pins.
4) Insert two 1/2" carriage bolts through the top and bottom mounting holes, and tighten their nuts.
5) Remove the two alignment pins, and replace them with the other two carriage bolts.

I think this is a lot harder to say that it would be to do, but the tradeoff between the single pin and four bolts in my mind is, how often are you going to change weights. If I thought I was going to be adjusting the weight often, I would be inclined to use a single threaded rod, but if I am going to pretty much always want this weight, I would rather use four bolts. The single bolt requires a bit more work at first, but makes changes easier, but the four bolts is really not unmanageable.

Another minor concern: If you use the single adapter plate to adapt to one threaded rod, you cannot see the four carriage bolts as easily to know if anything goes wrong with them, but then I'm not very concerned about that.

Another approach occurs to me as I sit here typing. The problem you would have is preventing the carriage bolts from sagging and the weights from falling off the bolts.
1) Figure out the spacing between the inner wheel walls and the weight disks (about 3/8") and put an approriate diameter steel guide pin in the bottom of the wheel opening at the 5 O'clock and 7 O'clock positions, held in place by the weight of the first plate.
2) Insert the carriage bolts, maybe using a couple of extra long ones in two positions at first, just as a precaution to make it harder for the plates to slip off.
3) Proceed to stack the plates one at a time. The bottom rest pins keeping the stack from sagging excessively until all four bolts can be secured.

In both these cases, the key is using something to accomplish the stacking up of the plates in proper alignment until you can get the carriage bolts tightened.

I do agree that the single pin is easier. I just haven't become convinced yet that I will do this more than once per wheel.

tomrscott · Jan 9, 2005

Re: 1/2\" Carriage Bolt Loading?

JJT,

I arrived at a desire for this kind of weight from reviewing some of the studies of tractor weight that you can find online. The general consensus I came away with is that with a 4WD tractor, you want to have about 100lb/hp of total weight, and distribute it about 40% and 60%, front and rear.

I realize that this will vary a bit with ground conditions, and other factors, but the JD 790 is way underweight for its power. The 2000 model I have is a 30 hp machine and weighs just over 2000 lb. for about 70 lb/hp.

My primary task is to grade and groom a very steep packed gravel driveway with complex turn angles for which I am going to use a top and tilt kit and a box blade. I have already driven the driveway without ballast and it is nearly impossible to get any engagement going uphill at all without slipping.

My other primary tasks are loader work where the 1000 pounds is a bit more than the minimum I could get away with, but will still be helpful. I am not going to be mowing a lawn or anything like that. Probably eventually getting a rototiller.

If I were just doing work on flat ground, I would be happy with 600 pounds or so, but my driveway surprises everyone who drives it for the first time. We've never had a single door-to-door salesman in 5 years here. /forums/images/graemlins/smirk.gif

JerryG · Jan 9, 2005

Re: 1/2\" Carriage Bolt Loading?

Tom,
I understand what you are saying about how you aim to install the weights. But, it is going to be harder to put the weights on with 4 bolts anyway you slice it. With the plate in the picture, you just have to hold the the mounting plate by it's self to put the 4 short carriage bolts in. The plate has a square cut in it to accept the carriage bolts. After that your plates can just be slid on, no alignment, no busted finger etc. If you go ahead with the 4 bolts, good luck.

Soundguy · Jan 10, 2005

Re: 1/2\" Carriage Bolt Loading?

( I don't think, however, that these are really in shear )

With them perp. to the load.. I'd can't help but imagine that they would be in shear.. however as we have all pointe dout.. the shear stress will be much less than the limits even for a soft bolt.. let alone 4 of them. Tension will also play a role here.. but again.. we aren't building a 300mph machine carrying nuns and children... just a 10mph? thing driving in a pasture..

If you did have side by side top bolts fail.. hard to say what the bottms may do. If soft.. I'd be inclined to thenk them may deform.. and then it would come down to the strength o fthe metal in the rim, vs the bolt heads. If they were hard.. I'd guess they'd snap due to vibration and loading.... Either way i don't see any 'catastrophic failure' scenerios happening..

Soundguy

Soundguy · Jan 10, 2005

Re: 1/2\" Carriage Bolt Loading?

( Mounting the plates is indeed going to be somewhat more tricky with four loose bolts )

What about putting the bolt thru the back of the rm.. and then use a jambnut to hold the bolt stiff.. then slde the weights on.. then add your washers and locknuts/lockwashers.. etc.??

Soundguy

tomrscott · Jan 11, 2005

Re: 1/2\" Carriage Bolt Loading?

Soundguy,

Thanks! Great SuggestionI had forgotten that the wheel mounting bolts would allow some space for that. Thought about that briefly at one point, but when I was thinking that I might need Grade 5 bolts, I was assuming there wouldn't be any threads at the bottom. I've noticed that even some cheap bolts don't always have the threads all the way down to the head, but I'll look and see what I can find. I guess I could even chase the threads down the shank with a die if I can't find a bolt with threads all the way.

Soundguy · Jan 11, 2005

Re: 1/2\" Carriage Bolt Loading?

As with the others.. I think you will be fine with g2 carriage bolts.. and they come threaded all the way.

Alternately.. you could simply buy some all thread stock, and make em exactly the length you want. it would take a few more nuts / washers.. but that stuff is cheap by the pound..

You may find that some rims already have square holes in them for weight plates. My old fords have square holes that fit perfectly with a carriage bolt.. Just make sure the hole is on a flat.. otherwise you will have to get creative with keeping the bolts 'straight'. I've cut pipe sections at an angle to make bolts stand straight on a beveled surface.

Good luck.

Soundguy

keeney · Jan 11, 2005

Re: 1/2\" Carriage Bolt Loading?

To put things in perspective, even mild grades of steel are going to have a yield strength of say 50,000 PSI. The 1/2" bolt has a cross section of something like 3/16ths of a square inch, so on a very crude ballpark estimate, its probably good for something like 9,000 lbs of force. Each bolt can probably hold up your whole tractor.

Grade 5's are going to be pushing 120,000 PSI. That gets you up to about 24,000 lbs each.

I would worry a lot more about the nuts coming loose than the bolts busting. I would also worry about deforming the wheel face if you tighten the wheel weights down against something uneven.

One nice thing about the harder grades of bolts is that the threads hold up a lot better when trying to wedge the bolt through a stack of heavy weights that you have to somehow hold in exact alignment on the face of the wheel while you pound the bolt through.

Anybody see the commercial where they show a single bolt that they use to hold on the bed lifting up the whole pickup? I remember it looking to be less than 1/2".

- Rick

keeney · Jan 11, 2005

Re: 1/2\" Carriage Bolt Loading?

I used cheap carriage bolts myself to add wheel weights made from weight-lifting plates to my to my JD 4100. I only added 125 lbs per side (5 each 25lb plates per side).

The holes in the wheel were setup for 1/2 carriage bolt, but I actually put the carriage bolt head on the outboard side of things because I hated the idea of bolt ends sticking out the side of the wheel face where they could easliy snag my leg walking past the machine in the garage, getting on and off, etc.

Photo - Wheel Weights with Carriage Bolts

- Rick