Turning radius Geometry lesson

hazmat · May 3, 2002

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 · May 3, 2002

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 · May 3, 2002

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 · May 3, 2002

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 · May 3, 2002

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

PowerMax · May 5, 2002

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 · May 5, 2002

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 · May 5, 2002

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 · May 5, 2002

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 · May 5, 2002

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.

TresCrows · May 5, 2002

I am pretty sure you cannot mix R4 and turf, there may be a possibility with rear bar turf and turf front.
I should think the radius would increase as speed goes up and that scuffing would increase also as speed increases.
Perhaps try reducing your front tire pressure a bit. I reduced mine. I remeasured my 2410 diameter today. I can get as low as 68 inches but that is turning slowly and with the wheel hard over. It does not seem to tear my fescue/clay lawn. Sometimes my turn leaves an elliptical (slightly) uncut grass area--this could well be front tire slipping or me just letting up on the sateering wheel a tad. Please don't take this the wrong way but I think a 2410 size machine is about as big as I would want on my lawn and it is really to big--of course it is my lawn so I get to decide--others may vary. Of course, now, if it is wet the 2410 and BX will both make a big mess. I am thinking also that R4 tires are nice but I think I would have preferred turfs and may buy a set. J

bubenberg · May 5, 2002

time to sell and join our ranks ... you are already an honorary pter ... our squadron commander will give you a few lesson on the way down to tazwell and on the way back home you can come by my place and qualify to drive your new aquisition with two wing mowers in tow (kunz eng. acrease 57 inches wide swat each).

ronjhall · May 6, 2002

Glenn
The diameter of the uncut circle decreases as weight on the front (the FEL) increases 

I think this is because the added weight gives more traction.

 And you are saying the diameter also decreases as throttle rpm's decrease? 

Not throttle, but how fast tractor is moving forward. Slow down and the diameter gets smaller.

 but I do have loaded rears and I don’t have problems unless I try to cut a maximum turn. 

Slowing down seems to help to stop the scuffing.

When measuring the circles cut. The radius only changes from my minimum to your maximum diameter by a radius of 5 ½ “. There are only a couple of places on my lawn where that is going to make much difference.

I run with pedal to the metal all the time unless I’m close to something I don’t want to hit. /w3tcompact/icons/eyes.gif

ronjhall · May 6, 2002

TresCrows

I am thinking also that R4 tires are nice but I think I would have preferred turfs and may buy a set

When you get the price. You may decide to buy another tractor. /w3tcompact/icons/laugh.gif

hazmat · May 6, 2002

As a point of reference, I measured my 1978 John Deere 316 garden tractor (48" cut) uncut diameter, It was a whopping 11 feet. It has manual steering making the forward / reverse shuttle that much more difficult. My dad's honda 4514 lawn tractor (38" cut) uncut diameter was about 40".

It looks like anything is going to be an improvement over the 316.

Hazmat

looch · May 6, 2002

B7500 with 60" RFM, uncut circle 10'2" /w3tcompact/icons/grin.gif

TresCrows · May 6, 2002

I might just do that, all things are possible. I know some teens that steal stereos and mag wheels, maybe I could just hire them to steal yours /w3tcompact/icons/shocked.gif , but I would not do that. J

PowerMax · May 6, 2002

B7500 with 60" RFM, uncut circle 10'2" 

Now try it in reverse and see what you come up with. /w3tcompact/icons/laugh.gif

Jeff

Anonymous Poster · May 9, 2002

Leave it to old 3-crows to point out other threads on the subject. If your going to point out threads give us the name and date, otherwise just answer the question. What is uncut radius???