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Hydraulic PTO?
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Bernoulli
posted
Dear everyone,

I am working on my final bachelor project and I have a few questions about hydraulics...

I want to design a standalone PTO cart that can be pulled behind an ATV. I have found there is a reasonable demand for this. But I am wondering what would be the best way to power it. One of my ideas was to put a stationary diesel engine on the cart that will be connected to a hydraulic pump and motor. The hydraulic motor will be connected to agricultural machines to power them. The output of the hydraulic motor should be around 15-20 hp. I am not very familiar with hydraulics so I am wondering what your thoughts about this are. How much hp does the diesel engine need? Is a hydraulic transmission practical in this case? Would you advise it to do it differently and how? If this is a good idea, what parts would I need to get it all properly working? Any of your thoughts are very welcome.

Kind regards,

Lyor van Vliet

This is the concept in CAD
 
Posts: 3 | Location: The Netherlands | Registered: 10 June 2011Reply With QuoteReport This Post
Pascal
posted Hide Post
Do you want a constant RPM of 540 on the PTO? If yes you will probably find that a gear box will be less expensive and also less complicated. Would also suspect will be smaller and weigh less.


Roy
 
Posts: 249 | Location: Winnebago, IL | Registered: 26 April 2010Reply With QuoteReport This Post
Bernoulli
posted Hide Post
Thank you for your reply.

I would like to have a variable RPM so the PTO can be connected to any agricultural tool (from hay balers to hay bobs). Would it be a good solution in that case? The machine should be as light as possible since the most powerful ATV's can only pull 500 kg max and a hay baler is already 385 kg.
 
Posts: 3 | Location: The Netherlands | Registered: 10 June 2011Reply With QuoteReport This Post
Pascal
posted Hide Post
Not familiar with the netherlands but here in the USA PTO speeds are either 540 or 1000 RPM on ag equipment. Varible speed is done with the engine. The Amish use diesel engines mounted on carts to operate their equipment. It sounds like you want to do something similar except pull it with an ATV.

I guess a really dumb question but why use the ATV Vs a small farm tractor? They already have the PTO,3-point hitch, hydraulics, etc and are meant to be used for this type of work. There are several companies that make Ag tractors in the 25 HP range and these also have FWD also. These Only advantage I can see with an ATV would be road travel speed.

You will find that using hydraulics will cost you around 20 - 25% or more loss in power transfer. A rule of thumb for reference is that it takes one horse power to pump one GPM at 1500 PSI. So based on this if you want 20 HP output from a hydraulic motor you will need 25 HP or more input into the hydraulic pump. You will also need a reservoir and potentially some form of oil cooler.

For this a closed loop hydrostatic transmission would probably be the easiest to build since they would have infinite speed control and potentially be semi-self contained for speed control. Adjust pump control to give desired RPM of the motor and unless your load changes significanty your RPM should stay relatively steady.


Roy
 
Posts: 249 | Location: Winnebago, IL | Registered: 26 April 2010Reply With QuoteReport This Post
Bernoulli
posted Hide Post
Again, thanks a million for your reply. I am not very familiar with all of this, I've been trying to read up on most of it but it's hard to remember all of the details, so your posts are worth a lot to me (I don't have a lot of time to search for everything on my own).

The question is not dumb at all; the ATV won't be there to replace the small farm tractor. My idea was to make the ATV more functional. Hitches already exist for any brand of ATV, and they are being used for a lot of purposes as well. The product is meant for people who already have an ATV and don't really need a tractor. They can use it to make small hay bales for their cattle (in my imagination horsey people could be interested in it) or power other equipment with it. It is not meant to be used on a large piece of land to replace the tractor. I've done some market research and I have found there would be a decent demand for such a product, if the price is right of course.

I was not aware that PTO speeds are either 540 or 1000 RPM. I've googled it and there are actually only 3 speeds for PTO's: 1000, 750 and 540 rpm.

But there was another reason I thought a hydrostatic transmission would be practical. A lot of ag. equipment also need hydraulics... I thought it would be easier to take a hydrostatic transmission and drive the PTO and the hydraulics with it. Would that be possible? And if so, how would you recommend it?

This message has been edited. Last edited by: vanVliet,
 
Posts: 3 | Location: The Netherlands | Registered: 10 June 2011Reply With QuoteReport This Post
Pascal
posted Hide Post
Is the 750 RPM PTO popular in Europe? Here in the USA I have never seen an implement designed to run at 750.

Here the 540 RPM is used on equipment of less then 100 - 125 HP so I would suspect similar findings in Europe.

Yes, I think a gear box would be a better choice for this application. Is the Netherlands getting stricter on oil leakage onto the ground? If yes then gear box gets another vote in its favor.

This message has been edited. Last edited by: oldnslo,


Roy
 
Posts: 249 | Location: Winnebago, IL | Registered: 26 April 2010Reply With QuoteReport This Post
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