I saw that there is a reference to ISO 730-1:1994 so I looked at that. Appears that they are identical - so that doesn't help.

What I think they are trying to state is the minimum lower hitch points that the +/-5° mast inclination range can be measured at.

- Low point: Note that the "Mast adjustment height, lowest position" is the same as the "lower hitch point." Looking at a CAT-I this means that you must to have the ability to adjust mast inclination at least +/-5° at 200mm above the gound. If you can still get +/-5° at a lower point its gravy. Realize that due to the geometry, the lower you go the harder it is going to be to get the +/-5° range.

- High point: Again looking at CAT-I, you must have the ability to adjust mast inclination at least +/-5° with the "lower hitch point" at 508mm or more above the gound. And similarly, due to the geometry the higher you go the harder it is going to be to get the +/-5° range. The geometry is designed to kick the rear of the implement up at the high lift range to facilitate transport of long implements (i.e. plows).

ISZ

Dear IceStationZebra,

thanks a lot, with your explanation I have understood it perfectly. The ISO standard is equal to the ISO you looked at. What a pity ISO didn't provide any picture for it.

Cheers

Your welcome. ISZ

Hi all,

another question regarding to the ISO 730-1 or the ASAE S217.12. Are they mandatory? Do companies have to design a three point hitch in according to this standard or not? I haven't found any refereces so far.

thanks

Pietro

"ASABE Standards, Engineering Practices, and Data are informational and advisory only. Their use by anyone engaged in industry or trade is entirely voluntary. The ASABE assumes no responsibility for results attrib-utable to the application of ASABE Standards, Engineering Practices, and Data. Conformity does not ensure compliance with applicable ordinances, laws and regulations. Prospective users are responsible for protecting themselves against liability for infringement of patents."

The SAE, ASAE nor ISO can make standards a requirement. Realize that all of these organizations use people in the respective industries to come up with the standards that they will use. What this basically means is that there is very little outside oversight, unless it concerns the public good. (automobile crash regulations, engine emissions, etc.)

This is where homologation comes in. What you need to do is find out if the country where you want to sell your equipment makes them mandatory. Individual governments can make them mandatory, or go above and beyond!

The EU is a prime example. There are the "directives" that cover any machine sold in the EU. A few of the main ones are:
DIRECTIVE 2006/42/EC - machinery directive
DIRECTIVE 2005/88/EC - noise directive
DIRECTIVE 2002/44/EC - vibration directive
DIRECTIVE 74/151/EEC - tractor directive
In theory these are all you have to meet, but in reality some countries go beyond this, often contradicting ISO standards and directives. Italy is a good example of this. If you are going into Europe I would strongly suggest getting a company like TUV involved.

And then there are countries like the USA where standards may not be required by law, but if someone gets injured and you don't follow the "voluntary" safety standards you will loose a lot of money in court cases.

ISZ

Hi IceStationZebra,

thanks for your reply. I got it. In the directive you have mentioned, any ISO standard isn't mentioned about the three point hitch, but few companies in their tractor datasheet write the three point hitch category, so it should mean the most of them don't follow any standard, right?

Best regards

Pietro

It would help a lot if you told me which country or countries you are interested in. They probably don't mention it because it has been the standard so long that it is assumed, but as far as I know all the large tractor manufacturers in Europe, Australia and Americas follow the 3pt standard.

In reality it is probably tough to meet all the 3pt requirements considering all the other options and tire choices that are offered in the various markets. I wouldn't be surprised if they cut corners a little, but you would have to measure very carefully to find out.

ISZ

thanks for your reply, I'm interested in the whole EU. But isn't a tractor sold with only one front and rear radius index?

What do you mean by radius index? ISZ

Hi IceStationZebra,

I'm sorry for the delayed reply I was on holiday. By the way for the dynamic radius index I mean the radius that it is used exclusively for the calculation of forward ground speed during homologation procedures.

OK, you are talking about the tire rolling radius. I have never been involved with the homologation of a tractor, but my assumption is that you would have to take whatever the worst case is for the size of tires offered. Some aspects of homologation will be worse off with tall tires, others with short ones. This is what I had to do for a articulated loaders.

You also have to consider other options. Will you see different performance with a "quick hitch"? What about two wheel drive vs. MFWD, claw vs. ball ends, 540 vs. 1000 rpm PTO, etc. Some tractors have multiple holes for the top link, meant to increase the tipping action with long implements like plows. Many tractor chassis also come with different classes of 3 pt. hitches, depending on the power. For example, it is very common in North America to find tractors with class 3 and 4 narrow.

ISZ

Hi IceStationZebra,

thanks for your reply, does the rolling radius change on the several configuration for a specific tractor?
what do you mean for " to increase the tipping action with long implements?".

thanks

Pietro

The rolling radius will only change for different tire configurations (size, brand, ply/radial, mpa, wear, duals, etc.). There of course will be minute changes due to gross vehicle weight differences, but they will be minor. And if you are taking measurements will real tires, you will have to account for variations amoung tires, even of the same brand & model. (and it can be significant)

My comment about the different configurations is that you will have to review if, for example, the pin center for attaching the implement to the lower arms moves between configurations. Different tire configurations will alter the pitch of the tractor. Some tractors have both 540 and 1000 rpm PTO shafts, at slightly different heights.

As far as tipping action goes, I am specifically talking about how the geometry tips the implement forward as it is raised. If you have a long implement like a 6 bottom plow you may want to increase the tipping action to increase road clearance for the last bottom during transport.

ISZ

Thanks IceStationZebra, I got it. why is the regulation of the lift rod pivot point on the lower links introduced?

It appears mainly so they could introduce the idea of adjustable lift rods. ISZ

But lift rods are adjustable. weren't they in the past?

I wouldn't be surprised if there were a few tractors without, but the vast majority have had at least one adjustable rod. But what I was really getting at is that to define adjustable lift rods you first have to define what a lift rod is.

ISZ

Hi IceStationZebra,

I was again on holiday. Btw the lift rod regulation was introduced in order to enchance the three point hitch connectivity, right?

I think the main reason for adjustable lift rods is so you have some adjustment when plowing with one wheel in the furrow. I have never used it for any other reason. I guess you would probably use it on any implement that is nonsymetrical.

ISZ

Thanks for your reply. Regarding to the three point hitch design, I have found this paper, https://kb.osu.edu/dspace/bitstream/handle/1811/49...

where a CAD tool has been created to help the designer to design a three point hitch able to follow the ASAE S217.12 standard. In the three point hitch design I think it is also necessary to take into account the lifting perfomance measured in according of the OECD code. There I created a tool to design a TPH. Would it be useful for designers to take into account to design a three point hitch?

I have another doubt regarding the three point hitch. I'm looking to nebraska test report of some tractors and I noticed the three point hitch can lift a load higher than the tractor stability limit. (As example check the CASE IH Puma 155). This sounds weird to me, since it's not a safe working condition. Why are three point hitch designed to develop so high lifting loads?

thanks

Pietro

I have seen the test done with a bare tractor frame with no engine or tires bolted to the floor. There are no stability limits in the testing so the tractor manufactures keep pushing the limit so they can claim to have the strongest tractor. Which, like you pointed out can get silly.

In reality you don't want a lack of lifting force to be lowest limit in your system. This will make customers think you have a weak tractor. Farmers will add weight to the front of the tractor to offset the lack of stability. (water/salt mix in tires, iron weights) I have seen large water tanks mounted to the front just to add ballast. On the negative side this is stressful to the tractor structure, adds to soil compaction, and burns extra fuel.

ISZ

I noticed all companies are set up to a similar lifting force for the same tractor type. I was wondering why just that lifting force was choiced by producers. I think somehow it's the force necessary to lift the implement at a specific vertical acceleration. Do you think it's a good argument?

Many tractors have the ability to adjust the lift/lower velocity, especially with automatic draft control. Of course the acceleration rate comes into play with this control loop, but I can't recall ever observing any significant acceleration/deceleration control ramp. They are usually fairly abrupt.

I'm not suprised that similar tractors from different manufacturers have similar lifting forces. As customers compare specifications nobody wants to appear lacking. There are always the 1% of customers that will push the limit, but like you suggested previously there is a practicle limit that most customers will not exceed.

ISZ

Thanks for your reply. I got the point. So when designers design a three point hitch, what do they take into account?

Being cynical, I would say the competition! ISZ

mmm but how can they beat the competition?

By the way...I found an old paper, where it's written it is necessary do apply two times the gravity force of an implement to remove it out from the ground. Taking into account the heaviest implement , I get the same order of size of the maximum lifting force for a specific tractor size

Hi IceStationZebra,

I have just realized that in a normal implement the CoG is moved rearward than the one used at the OECD test. Therefore in normal working condition the lifting force is lower than the one measured with the OECD test. What do you think about it?

thanks

One has to realize that these standards are created by representatives from the companies who are selling these products, not independant engineers or scientists. And as such they all have an interest in making their products look good. They could have chosen a distance that was farther back, but then the number would be smaller and infer less strength. Sometimes the standards come from a group that already has a standardized process, maybe has done some comparative testing, and the others just agree to adopt it. In this case it may have come from the Nebraska tractor test, but I don't really know.

I can tell you from experience that some things are very black and white while other aspects are not. One example is taking production varience into account. If you did a statistical analysis of your 3pt hitch design there is probably a +/-0.5% possible varience. Though the difference is small, what number gets put into the sales literature?

ISZ

IceStatioZebra, thanks for your reply, you're right, also to understand there no information to understand why the ISO or the OECD choosed a specific test set-up. About the variance no number is put in the sales literature...