Weights outside of wheels affecting balance

[fishydeals]

We have a 165d yanmar however for this question the tractor type/make is irrelevent. I got a post pounder for this tractor which is maxes out the capacity of this tractor but we don't have miles of fence to do so it works for us. The post pounder works fine and the tractor carries it around fine but I have a sense that it is very tippy as the post pounder is quite a bit taller than the tractor. So i wanted to add rear wheel weights to the tractor. I already have about 120# on the front which keeps the front on the ground and the manual allows for 110# on each rear wheel. I wanted to make concrete weights as others have done but the problem is that they would stick out about 5 inches past the outside of the tire. Weight is weight but i was wondering that if the weights stick so much from the wheel whether that would not really help the tipsiness. I don't know whether I'm making something up or this is an actual concern. From a center of gravity perspective it won't change anything but in practicality I feel it might.
Any thoughts?
Luke

 

[oldnslo]

Since weight would be same on both rear wheels wouldn’t the weights kind of cancel each other for tipping?

 

[rScotty]

A wonderful tractor. We sure miss ours. I don't think that adding those weights will make it more tippy. The weight you are adding has a CG below that of the post pounder.
Now if you do manage to tip it over, having weights will increase the moment since you would be swinging a larger mass through a greater arc... but practically I don't think that should be something to worry about.
I'd add the weights.

The YM165D had several ways to widen the rear stance - including reversing the wheels - which required that the left and right wheels swapped side, and made the hub fixing bolts end up on the inside rather than conveniently on the outside. There are pictures in the ownerss manual.

At max. width, the wheel & hub are reversed with the hub to the inside so that from the side of the tractor it looks like the photo below. If you do that, be sure to reach inside between the wheel hub and fender to check and keep those two wheel-to-axle set bolts tight. Those set bolts should stay tight eough to take up all of the play between the wheel hub and that six-sided axle. The springs Yanmar put around the bolts work like lock washers to keep the bolts snug.
luck,
rScotty

 

[fishydeals]

Since weight would be same on both rear wheels wouldn’t the weights kind of cancel each other for tipping?

Thats what I thought but I was doubting myself...
Probably if someone did all the physics it could have some effect in extreme circumstances but in practically your both probably right.

The YM165D had several ways to widen the rear stance - including reversing the wheels - which required that the left and right wheels swapped side, and made the hub fixing bolts end up on the inside rather than conveniently on the outside. There are pictures in the ownerss manual.

At max. width, the wheel & hub are reversed with the hub to the inside so that from the side of the tractor it looks like the photo below. If you do that, be sure to reach inside between the wheel hub and fender to check and keep those two wheel-to-axle set bolts tight. Those set bolts should stay tight eough to take up all of the play between the wheel hub and that six-sided axle. The springs Yanmar put around the bolts work like lock washers to keep the bolts snug.

Actually when we got the tractor the hubs were inverted and set to their widest stance. However I narrowed them because I was afraid it would strain the bearings too much. In the manual it doesn't show the hubs inverted and sets the max width at 33.5 in. If the hubs are inverted you can obsviously get way more than this. Currently I have I 36.5in and could increase by 5 in more if I went to the max. I'll do the weights and maybe in very rough terrain I'll push the wheels out to the max width. I probably won't work much on hills but in a pristine meadow that is full of holes and soft spots and that is the concern.
And increasing the moment would be a positive because it would tip slower providing more time for an escape... not that I want to try
Ok thanks guys, I'll give it a try and always take it easy. But so far I love the tractor.

Luke

 

[fishydeals]

Actually my wheels are bolted on the outside of hubs which means there is no lip for the wheels to rest and they rest on the bolts alone, probably not the best but so far they stay tight...

 

[rScotty]

Actually my wheels are bolted on the outside of hubs which means there is no lip for the wheels to rest and they rest on the bolts alone, probably not the best but so far they stay tight...

Bolting in that way does give a little less support, but should be OK. The wheel to hub bolts should be tight enough to prevent any motion between hub and wheel...and therefore no problem.

The thing to keep an eye on are those two compression set bolts with the springs around them - and the 14?mm safety with its lynch pin or cotter If the set bolts loosen, all that holds the wheel on is that safety . It does prevent the wheel from leaving, but allow the axle to wallow out the broaching in the hub. That wear can slightly increase the lack of concentricity between the wheel and the axle. But that is a pretty heavily built little tractor.

I hear you on the axle loading being something you are concerned about when moving the wheels out. However, those outer axle bearins are pretty big and I don't believe that the outer axle bearing is acting as a single cantilevered pivot. Issn't there an inner bearing on the differential that also supports the axle? I don't have my old parts book, but moving rear wheels out even a few inches does gain you a lot of stability.

I finally went to turf tires on ours just for the extra stability. Living in the mountains we can't avoid slopes.
rScotty

 

[fishydeals]

Probably there is more than one bearing in there... Honestly don't know but considering a post pounder is more stationary than mobile it should be fine. We live in a plateau so not much mountains but we're still developing our property so lots of ruts, holes, bumps, mud, rocks, and stumps... Dangerous as you can't always anticipate. Ours can with turf tires which I don't complain about. Will keep an eye on those set bolts
Thanks

 

[SmallChange]

Since weight would be same on both rear wheels wouldn’t the weights kind of cancel each other for tipping?

They cancel each other as far as making one side of the machine heavier than the other. But, they will probably lower the center of gravity. It is very likely that for tipping purposes you could model the mass of the tractor as being at one point somewhere around the middle and higher than both axles. If you are on a slope that is so steep that that point is outside of the footprint of the tires on the ground, the machine will tip. Adding wheel weights will lower that point. In the limit as you put infinite weight on the rears, the point will approach the center of the rear axle from above. So, wheel weights would tend to make it harder to tip the machine.

A better way to lower the center of gravity would be to mount a heavy skid plate on the very bottom of the machine, lower than the axles. If you max out the machine's weight capacity with such a plate it would be pretty hard to tip.

If you had a special purpose machine that always wants to tip one way, such as for driving down the right shoulder of the road with a mower out on a boom to the right, you could definitely improve tipping resistance with weight on just one of the rears.

 

[California]

On my YM186D (about the same size) I sanded the 'wrong' side of the hub flanges to make them flat and found they were already machined flat. Apparently Yanmar anticipated the wheels might be installed that way, outboard beyond the hubs.

This improved the width of the tread to maximum.

Then I added wheel weights from Craigslist - origin unknown - that fit outside the shoulders in the rims.

Geometry - I think more weight on the uphill side of a potential rollover has far more effect than equal weight on the downhill side since it has farther to travel. That downhill side is only a couple of inches beyond the fulcrum (tire).

Note adding weight on the wheels avoids the stress on axle bearings that is increased, if weight is bolted on/under the tractor chassis.

 

[Mike1955]

On my YM186D (about the same size) I sanded the 'wrong' side of the hub flanges to make them flat and found they were already machined flat. Apparently Yanmar anticipated the wheels might be installed that way, outboard beyond the hubs.

This improved the width of the tread to maximum.

Then I added wheel weights from Craigslist - origin unknown - that fit outside the shoulders in the rims.

Geometry - I think more weight on the uphill side of a potential rollover has far more effect than equal weight on the downhill side since it has farther to travel. That downhill side is only a couple of inches beyond the fulcrum (tire).

Note adding weight on the wheels avoids the stress on axle bearings that is increased, if weight is bolted on/under the tractor chassis.

It might work better, if you can set it up each time you move the machine. And also if the machine is moved for working and hit a small low place. Katie Bar the Door