Turning radius Geometry lesson

[hazmat]

I'm trying to compare specs as I research buying a tractor. I've been frustrated trying to compare the "manuverabilty" of the different models. From the posts I've read, I believe people have been using terms radius and diameter interchangebly.

Here's the geometry lesson: The diameter is all the way across the circle, the radius = 1/2 the diameter.

I will try to remember to bring my tape measure as I visit the dealers. In the meantime I want to know / confirm the turning diameter and uncut circle diameter (assume 60" deck) of the following models:

BX 2200 turn dia 195", uncut 75"
JD X575
JD 4010 (I know I'm not going to get any answers here)
JD 4110 (could subsitute JD 4100 here)
NH TC18 turn dia 166", uncut 46"
NH TC21D turn dia 182", uncut 62"

All numbers I've included are calcs based on manufacturers published turning radius I'm not sure that the calculations are correct (the published specs should be the largest arc created by any part of the tractor, I am assumming that the arc is created by the wheels), but here they are.

Turnind dia = (turning radius + deck protrusion) *2
uncut dia = (turning radius - width - deck protrusion) *2

The diameters should be easier to measure, make a circle with your tractor and then bust out the tape & measure the tire track circle. Be sure to add the amount that the deck sticks out beyond the tires. The uncut circle requires less math, but requires that you remember to do it before you cut the grass.

Think of it as an excuse for more seat time.
If your neighbors think you've lost it as you are doing donuts in the front yard, you can explain to them that you are participating in a nationwide study sponsered by TBN that will benifit the human race for years to come.

If you have another tractor model & want to post its measurements, I'm sure others will find it useful as well.

Proffessor Hazmat (sometimes being an engineer is a curse)

 

[TresCrows]

Dude, their are several threads on this already. yes, I know the difference but with two tractors and all the specs and others I have looked at it does get confusing. To the best of my memory my BX with 60MMM gave a 60 inch uncut diameter. My 2410 with 60MMM gave a uncut diameter of 72 inches. I have driven a 4100 and I would say it may not turn quite as sharp as my 2410 but really it is very close give or take. J

 

[hazmat]

trescrows,

Thanks for the info, I've read some of the other posts, and I had trouble figuring out if people were talking about radius or diameters. I'm probably overanalyzing, but I was looking for a quantitative comparison of the mobility of the BX vs. the small utilities. It appears that my math doesn't give the right answer.

Hazmat

 

[skipperbrown]

I measured the cut on my bx2200 w/ the 60" mmm and got about 72-74" minimum diameter circle. It was tough to tell exactly because the grass really didn't need mowing when I made my measurement and I had trouble finding the edges. I was a bit surprised it wasn't tighter.

mark

 

[glennmac]

The uncut circle with my B2910 and 72" mmm is 83".

 

[PowerMax]

glennmac,

Do you have R4's on your 2910? If I make a tight turn with mine - it leaves a major berm from the outside front tire. Do you have this problem?

Jeff

 

[glennmac]

PowerMax,

Yes, I have R4's, although I don't like them and wouldn't get them again if I had it to do over. Yes, scuffing can can happen when the front wheels are turned but they don't pull cleanly around in a circle, but instead are pushed into a sideways slide by the back wheels. I can eliminate all scuffing by the following:

1. Don't mow when the ground is soft from wetness.
2. Mow in 2wd, not 4wd.
3. Mow with the FEL off to lighten the front.
4. Don't try to stay in a tight turn all the way around a tree, bush or corner. Turn a little, back up a little, turn a little more, back up a little, then finish the turn. The turning and backing is made very easy with the HST and avoids sideways sliding by the front tires.

 

[PowerMax]

Glenmac,

Thanks for the response. I just wanted to confirm that this was normal and not just exclusive to my 2910. Unfortunately, I had to mow (6 times so far) when the ground was still wet in some spots. However, it even scuffs in the dry areas. I'm trying to remember not to flip right around trees and stuff to avoid the "pushing" effect. Those front wheels will turn very sharply and its easy to do with the power steering. I generally have it out of 4WD when mowing and never mow with the FEL on. I'm already onto the forward and back action to avoid the sharp turns - but, that is a pain in the neck. I wonder if its possible to mix the tire options - e.g. - mount turf tires and rims onto the front? I thought maybe I have read that this is not an option - due to 4WD windup or something. I guess I have to live with it now, but - I sure do have to do a lot of turning with all the obstacles I have to mow around. Hopefully, it will get less severe throughout the summer, as things dry out.

Jeff

 

[ronjhall]

Glenn
After seeing your post of 83” for your 2910. I thought I would measure mine again. Fist time I got a measurement of 72”. I had FEL on, rear wheel spacers and rear weight box and running at a slow pace.
Yesterday I did the same test with weight box, wheel spacers, slow speed and no FEL. My tractor has turf tires. Radius was 78”.
When I pick up it full speed at PTO rpm and mid-range rear the radius moves up to your measurement of 83”.
Like you I have found that driving in different directions at something I want to get close to is the best way.
I have started to use a weight box whenever I mow the lawn. It has cut down on the scalping by the front tires.
I’m going to take the rear wheel spacers off this week. I’ll check again to see what the diameter is.

 

[glennmac]

Ron, that's interesting. The diameter of the uncut circle decreases as weight on the front (the FEL) increases. And you are saying the diameter also decreases as throttle rpm's decrease?

I never thought about weight in the rear affecting scalping by the front tires, but I do have loaded rears and I dont have problems unless I try to cut a maximum turn.