6m 750a changing offset

[Simon Chiles]

Good point. Now I'm getting nervous that the thing still isn't square and it's out of warranty.

In the discussions we’ve had over the phone about this problem you’ve never mentioned that the frame wasn’t straight. Undoubtedly this is your problem ( or more correctly JD’s ). Easiest way to check if it’s square would be to park the drill on concrete and then with a plumb line and spray paint mark the position of the pivot pin on the drawbar and the outside centre point of the outside wheels and inside centre point of the inside wheels. Also mark the mid point between the axles ( ie centre of the drill on the axle line) once you’ve marked all the points with the spray paint ( needs to be a pin point for accuracy ) pull the drill forward so you can measure the four triangles, pivot point to axle centre point then inside and outside tyre centres for both left and right. I’m sure you can apply Pythagoras to quickly calculate whether it’s square or not.

 

[Wheatseeker]

The other thing is that our drill chassis was misaligned and had to go back to the JD dealer to be professionally re-welded. It looked like they corrected it, but maybe there's some residual problem. .

Have you tried testing the drill alignment on a hard surface in the same way you would test a tractor autosteer? If the tractor returns exactly down the same path in both directions and the drill does the same, that would rule out GPS errors and the rear wheel alignment. If it doesn’t you’ve found your problem.

 

[Will Blackburn]

I reckon if a wheel(s) is out of alignment then that would bring coulter pressure/depth changes into play with the variable alignment.

 

[Bman]

With my rapid on Gps it pays to check offset on every field, twice on big fields also good practice as checking depth at the same time, stop the drill and have measure up mid run. Never run at full width knock 1 or 2 cm off. Your bent back wheel is a constant in all conditions drilling depth and soil conditions are not which will affect things more. IMHO get read of your linkage attachment and pop a draw bar pin in it always seems to give a cleaner straighter pull but then that might not be an option on the drill design.

 

[Fish]

It's difficult to work out how the drill could be doing this because the 4m would be worse if it were down to their being 2 more coulters being right handed. Probably worth a quick measure from the draw bar pivot to the front corners on each wing.

This is simply not right, well on our 4m it ain't, we have 12 right and 12 left, the drill just pulls straight.

 

[Feldspar]

Has anyone measured their drill yet? @Timbo @Tractor Boy

Going to do it this week now we have cleared some grain storage space.

 

[Tractor Boy]

Has anyone measured their drill yet? @Timbo @Tractor Boy

Going to do it this week now we have cleared some grain storage space.

As far as I can see mine looks square( only done by chalk lines on a floor) it is,however 3.97 cm wide. I’ve reviewed my problem and think I need to tinker with the offset I’ve got on my tractor as I do appear to have 12cm joints one way and about 24cm the other side. This isn’t obviously helped by the CFX thinking the drill was 4m not 3.97.

 

[RTK Farmer]

Suggest if it hasn’t been said before that gps users do a (what Trimble call) Roll Calibration to check tractor travels accurately both ways on the same line before blaming the drill.

 

[Feldspar]

Suggest if it hasn’t been said before that gps users do a (what Trimble call) Roll Calibration to check tractor travels accurately both ways on the same line before blaming the drill.

Would that explain though why the offset required to leave no gaps changes from field to field?

Going to measure ours tomorrow so will have some idea after that.

 

[RTK Farmer]

No. If roll cal was out it would be the same everywhere. I just thought id throw that in though in case it hadn’t been considered. It probably should be checked at least annually or better once in spring and autumn.

 

[Robt]

James,
Roll cal is called mounting bias callibration and as ive advised it should be carried out at the start of each season or whenever you experience a problem to rule it out. The topcon screen will talk you through it. I have done it with you, its the one where we go up and down the same line three times, twice on auto steer.
Yours was done countless times last year to rule it out so i very much doubt its your issue.
You need to get it measured asap to ease your worry.

 

[Feldspar]

James,
Roll cal is called mounting bias callibration and as ive advised it should be carried out at the start of each season or whenever you experience a problem to rule it out. The topcon screen will talk you through it. I have done it with you, its the one where we go up and down the same line three times, twice on auto steer.
Yours was done countless times last year to rule it out so i very much doubt its your issue.
You need to get it measured asap to ease your worry.

Thanks. Have done mounting bias cal several times so know it's not that.

Measuring it right now.

 

[Robt]

dont forget.....Measure twice...cut once

 

[Timbo1080]

Has anyone measured their drill yet? @Timbo @Tractor Boy

Going to do it this week now we have cleared some grain storage space.

Sorry, missed this - I assume you meant me?!

We have not checked it yet. The tractor has not made it back on the drill since this was all questioned. We have some further mods to do to the drill before spring, so will absolutely let you know our findings when we hook it back on again. Sorry.

Tim

 

[Henry B]

Timbo we had a 6m 750 on demo last Autumn, and had the same problem as you. We noticed we had a bit of play in the tractor linkage, so set the GPS at 5.9m and then no gaps.

 

[H.Jackson]

I have bought a little laser line will mount it in the middle of the drill hitch to shine on the middle of the tractor, pto, to ensure the check arms are holding the drill dead centre.

 

[Feldspar]

Just a quick update to this issue. After spring drilling we had a spare fallow field in which to play around with the drill. Someone from the local JD dealer kindly came out to have a look whilst we did this. The exercise was extremely worthwhile and to my mind has solved the conundrum of the wandering offset. As might have been mentioned previously, the drill came out of the factory with a misalignment of at least the stub axle. This went back to be corrected, but in doing they shortened the distance from the main part of the frame to the axle. This in turn gave rise to an asymmetry across the two axles of the drill.

What became obvious to me in the field was that some of the time one drill wheel was in firm contact with the ground whilst the other was not. This of course creates a torque on the drill which in turn will tend to deviate the tracking of the drill. The full understanding came when we altered the coulter pressure. At very low coulter pressure the drill wheels are taking most of the weight of the drill meaning that all the wheels are firmly in contact with the ground creating no net torque. With the coulter pressure set to max most of the drill's weight is borne by the coulters meaning both drill wheels are off the ground. Where the problem arises is in the range of coulter pressures that we often use for cereal drilling. In this instance we saw the effect where one set of wheels was in contact and the other set were not. As the seed is used up this obviously will change slightly resulting in a different torque and in turn a different offset.

The above fully explains why we see a variable offset in different drilling conditions (no offset much when drilling into cultivated ground with low coulter pressure or with beans using high coulter pressure). It also explains the changing offset through the field (differing amounts of seed in the hopper and undulations in the ground causing one or both wheels to come in contact with the ground). It further explains why in the first year we did not see this problem in any big way. At that point, whilst stub axles were skew-whiff, the distance from the main frame the axle centres were nearly the same rather than an inch out.

So, overall, it's a bit of a relief to have solved the problem as I was really not prepared to shut our drilling width down below 6m. We have seen black-grass growing in the wider gaps and it has made our work look sloppy. The drill has now finally gone into the local JD dealer to progress the matter and I hope that JD will be sorting out the problem that was not rectified at the first attempt.

 

[Feldspar]

James,
Roll cal is called mounting bias callibration and as ive advised it should be carried out at the start of each season or whenever you experience a problem to rule it out. The topcon screen will talk you through it. I have done it with you, its the one where we go up and down the same line three times, twice on auto steer.
Yours was done countless times last year to rule it out so i very much doubt its your issue.
You need to get it measured asap to ease your worry.

The first thing we checked was GPS tracking. Drove up an AB line and then back down. First time we did it we were about 15cm out and I thought I was going to be extremely red faced having insisted it wasn't a GPS fault. Then remembered I'd still left the offset in from the last time we used the drill. Once that was taken out, it tracked absolutely spot on. Phew!

 

[SilliamWhale]

Whats the situation with you and the 750 nowadays then @Feldspar? Are you happy with it or is it not for you?

Reading a bit on here you seem to be saying the crops established with a 750 look crap all year but seem to come ok by harvest time etc.? Are you using then Claydon terroriser thing much? Are you doing much no till with it?

 

[Feldspar]

Whats the situation with you and the 750 nowadays then @Feldspar? Are you happy with it or is it not for you?

Reading a bit on here you seem to be saying the crops established with a 750 look crap all year but seem to come ok by harvest time etc.? Are you using then Claydon terroriser thing much? Are you doing much no till with it?

Very happy with the 750a apart from this tracking issue. As @Simon Chiles says, it is a very good drill for cultivated land. For more direct drilling situations, I much prefer it to our Claydon for cereals. Claydon is better at OSR and beans. Overall intend to keep it for the foreseeable future, but don't intend to do much more no-till. Some scratch till, but doing more cultivation. Have something a bit like Lemken Karat from Weaving at the moment which I like.

Some interesting yields coming out of this harvest. Going to wait until we're a bit further through before properly contrasting between different establishment technique. So far max-till land not doing as well as I had expected relative to shallow or no-till. No yields amazing though in cereals.