ok been wanting to ask this for quite some time...I noticed when I got my new 2320 how much bumpier it was than my 345 trying to mow my lawn..since it was late in the season and mowing was just about over with I never really got to use it much.... but even now when I take it our for a joyride waiting for some snow I find it is so rough to ride over uneven ground.....now my question is this when mowing season finally gets here again (removing FEL and with 62 inch deck only) can I lower my tire pressure for a more comfortable ride....and if I do what is the recommended tire pressure....also is this just the way it is going to be with this tractor....I'm telling you this tractor shakes the Be-jeebies out of you....
Shake and Bake...tire pressure recomendations
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oh gee good question how about this... mowing speed best I can come up with...or as fast as I can with out being shakin to bits....I can tell you this the 345 is alot smoother ride than the 2320...
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Do you mean that it is rougher when traveling at the same speed for the two machines?
Now, let's move onto tires. Turfs on the 345 and R4s on the 2320? This will yield a different ride as well.
And here is tire pressure reading.
http://www.greentractortalk.com/forums/showthread.php?1879-Tire-Pressures&highlight=tire+pressure
I should have. Mentioned. These. Are turf tires
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Newton's Second Law of Motion, F=MA, Force = Mass * Acceleration
The key figure here is the Mass. Your 345 weighed 700+ lbs. The 2320 is 1700+ lbs (both are base weights). Every bump you hit is going to be magnified as your tires absorb bumps and attempt to return to their original shape (volume). Short of installing a suspension system, you'd probably be left with letting a substantial amount of air pressure out of your tires to reduce this effect. Of course then you're at risk of popping a tire bead.
Suspension seat?
The key figure here is the Mass. Your 345 weighed 700+ lbs. The 2320 is 1700+ lbs (both are base weights). Every bump you hit is going to be magnified as your tires absorb bumps and attempt to return to their original shape (volume). Short of installing a suspension system, you'd probably be left with letting a substantial amount of air pressure out of your tires to reduce this effect. Of course then you're at risk of popping a tire bead.
Suspension seat?
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As long as we only mow with our 4110 (with turfs) we keep the tire pressure low in the back. With them at the upper range of the recommended pressure, the machine felt bouncy. It was almost like you were bouncing side to side. We do not mess with the fronts much as we put on the loader and don't want someone to blow a bead using it. This machine is used by three people, otherwise I would lower the front also.
This interesting point deserves amplification.
Tractor tires being both large and lightly inflated, they act as springs. So the whole tractor's mass is sprung weight, excepting the tire tread area. True, there's no formal shock-absorbing system, but there is quite a bit of loss in sidewall flexing and air heating. The tire always returns to net shape, but a lot of energy is lost in the process. In one kind of language, there is nil geometric hysteresis, but a relatively low coefficient of restitution - how high the ball bounces, so to speak.
The issue with not having a car-type suspension shows up with repeated bumps, as in driving fast on rough ground. Even without the perfect resonance that corrugated roads can produce (and that feeds back to deepen the corrugation), bounces can add up or cancel, and we notice the ones that add up. More sprung mass means more stored energy, so the bounces can be harder, especially since since hitting the next bump before returning to "neutral" means compressing a stiffer spring. At the same time, the increased mass can damp motion: a ten-ton machine will be shaken less by any given bump. So it may not always be a simple analysis.
Driving just a little faster sometimes takes the vehicle out of the resonance regime, if you feel safe trying that. Adding well-fixed weight front and rear increases both the total mass and the pitching moment of inertia, and a little might help a lot. With my previous tractor, I found that a BH in back and full loader bucket in front actually let me drive smoothly at much higher speeds over rough ground. Another reason to have an FEL even on a tractor mainly used for mowing?
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With my 2210, I run the turfs at max PSI for the loader (~26 front/~14 back). Once I am locked into mowing I drop the fronts to ~16 and the rears to ~10. Makes a big difference in the ride and traction is actually a little better. No problems with the tires coming off the rims or leaks, etc. Been doing this for 9 years with no problems.
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Kimqi,
I appreciate your response (no engineering pun intended) though I don't think we're really looking at anything particularly cyclic and certainly not resonant. For argument's sake, in this case, it's really more of a simple spring system. So, to expound on my original point, the smaller and lighter tractor has smaller tires and less air volume as opposed to the larger and heavier tractor with larger tires. The tires, as you concur, are acting as springs and the 2320's springs are simply larger (aka a higher spring constant "k" in the equation F=kx). Further, they are undamped so the effect on the 2320 is more pronounced.
With regard to adding weight, I wouldn't suggest this casually as a remedy. By adding weight just to combat the amplitudinal effects you are sacrificing control over the tractor in an emergency situation and also imposing more wear on bearings, bushings, structural members, etc by having to absorb the additional loading. Instead, I think I'd favor going slower, even though it's not as much fun...
And yes, RGD, having filled tires should reduce these effects and give you a more docile ride. Unfortunately, I don't think your lawn will be as enthusiastic about this solution since it has to bear more pressure from the additional weight. I don't know about your lawn, but mine definitely shows me its disdain for a heavier tractor.
My point was that a vehicle with a critically damped (in the formal sense) suspension experiences each bump as just a bump. In an under-damped system, like a tractor, successive bumps can sum constructively or destructively (again in the formal sense) to give more extreme displacement or impulse, or to cancel at least partially. Like any other sprung mass, the tractor certainly oscillates; most of us have experienced uncomfortable oscillation in pitch, and sometimes in roll or yaw, though people who aren't engineers or pilots might not mentally label them that way. Some people here know what it looks and feels like to "bounce" the fender of a car with shot shock absorbers; the resonance is quite apparent, though still highly damped. Tractors have only the damping of sidewall and tire-fill hysteresis losses. But since tractor tires are stiffer springs than those used in light passenger vehicles, the "bounce" is harder to excite with just hand pressure.
I don't wish to be argumentative, but a lot of people may read this thread, and extract misleading generalizations from a technical discussion they might not want to take the time analyze critically. Although a more-or-less rigid and bilaterally symmetric tractor on unsprung tires is not a very complicated dynamics problem as they go, I respectfully suggest that it *is* somewhat more complicated than you suggest. I'd be happy to take the discussion offline with other engineers/scientists who really want to explore these themes.
I wouldn't either. My point was that in a system of this complexity, it's not always obvious on casual inspection how adding a little more weight in specific places might affect dynamics in real-world situations, under a given operating regime of speed, loading and surface roughness. It's certainly the case that small changes in stiffness (e.g. tightening hitch links, adding transit pins to BH) can have a major effect on comfort and stability/safety. And it has been my experience, and that of many people I know, that sometimes going a little faster takes the machine (tractor, car, truck, whatever) out of a "bouncy" condition and into a smoother one where vehicle dynamics and surface roughness were badly matched at a lower speed. There is no substitute for (careful) experiment.
Naturally, this depends on the damage mechanism. I don't mow with the tractor, but have done a lot of heavy loader work across my most delicate lawns. At least for me, pressure effects on dry ground seem to self-heal after the first rain. The real damage is when a wheel spins, even just an inch or so. I've usually had best results working heavily loaded and in 2WD, so the driven wheels never spin.
YMMV...
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