Hydraulic Dune Buggy Design: Is My Math Correct?

[turbo]

I just read through this thread. Wish you had posted a few months back because an old friend of mine that died recently built an all-hydrostatic drive vehicle about 30 years ago. It was a tube-framed buggy with big wheels and all-wheel drive. He made it so that he could go fly-fishing in places that normally you'd have to walk to, wade through mud, ford streams, etc. Clever guy. He made custom gold jewelry using the lost-wax method, crafted some of the nicest hunting knives I've ever handled, and retrofitted Winchester lever-action carbines and rifles to shoot common handgun ammunition. It would have been a good excuse to get back in touch with the old genius and see what problems he ran into when making his buggy.

 

[larkinja]

I just read through this thread. Wish you had posted a few months back because an old friend of mine that died recently built an all-hydrostatic drive vehicle about 30 years ago. It was a tube-framed buggy with big wheels and all-wheel drive. He made it so that he could go fly-fishing in places that normally you'd have to walk to, wade through mud, ford streams, etc. Clever guy. He made custom gold jewelry using the lost-wax method, crafted some of the nicest hunting knives I've ever handled, and retrofitted Winchester lever-action carbines and rifles to shoot common handgun ammunition. It would have been a good excuse to get back in touch with the old genius and see what problems he ran into when making his buggy.

Sounds like quite a guy!

 

[turbo]

Sounds like quite a guy!

Very smart. He was about the first guy around to learn the ins and outs of VHF antenna sensitivity and directionality, and apply it in this very hilly rural area to help people get TV back in the '50s. He had a very successful TV antenna business when I was a kid, and he kept enough stock on hand to demonstrate on-site what they could expect with antenna A vs antenna B or C. Hell of a businessman.

His buggy was not fast IIR, but it could get him into places that Jeeps could not go, and he had a hydrostatic-drive winch to haul himself out if he got mired. The buggy was a two-seater with an over-head pipe rack to carry a canoe. He and his son had good times with that, I'm sure.

He was a very clever and artistic guy. One time when I dropped in he was carving a red wax positive model of a ring for a very prominent man in town. The guy's daughter had commissioned the ring to reflect her father's activities in the Masons, the Shriners, the Rotary, Lions Club, and other social organizations. I never saw the finished project, but it must have brought a smile to the old guy's face when he got it. The mold looked a bit busy, but well-organized. Val's work was top-notch.

 

[larkinja]

Very smart. He was about the first guy around to learn the ins and outs of VHF antenna sensitivity and directionality, and apply it in this very hilly rural area to help people get TV back in the '50s. He had a very successful TV antenna business when I was a kid, and he kept enough stock on hand to demonstrate on-site what they could expect with antenna A vs antenna B or C. Hell of a businessman.

His buggy was not fast IIR, but it could get him into places that Jeeps could not go, and he had a hydrostatic-drive winch to haul himself out if he got mired. The buggy was a two-seater with an over-head pipe rack to carry a canoe. He and his son had good times with that, I'm sure.

He was a very clever and artistic guy. One time when I dropped in he was carving a red wax positive model of a ring for a very prominent man in town. The guy's daughter had commissioned the ring to reflect her father's activities in the Masons, the Shriners, the Rotary, Lions Club, and other social organizations. I never saw the finished project, but it must have brought a smile to the old guy's face when he got it. The mold looked a bit busy, but well-organized. Val's work was top-notch.

Wow, that is very cool. You just don't meet people like that very often. I imagine for him, similar to me, its not about having the buggy, its about building it. There is something very satisfying about building something with you own hands, and the challenges it poses that makes it fun. Especially when it is something some people say can't or shouldn't be done. For me its also about learning new things. Short of the hydraulics on my plow truck, and a couple repairs on a bobcat, I don't know that much about hydraulics, so something challenging like this is a reward in itself. There are many things on my list to build, and each time I do one, I gain more knowledge and experience. My son is 6, and he is now starting to take interest in these projects, and I hope it evolves into a father/son activity that can last a lifetime and make memories. I remember one of my best friends in school did things like this with his father, and I remember thinking that I wish I had something like that with my Dad.

 

[drankin]

Did a little more work on the schematic. Added a flow divider and high-speed circuit.

 

[larkinja]

Its looking really good! One question. I have a Symbols chart here, but some of the symbols don't match exactly. Do you have a chart for the exact symbols you are using? I am attempting to put together a parts list as you add things to the schematic, and this would help me.

Also, as far as the schematic goes, this design uses a variable disp pump. What would be the implications of using an actual hydrostatic pump? Are they basically the same thing only with some of the circuitry built in? I was kind of looking at this pump as a possible candidate.

https://www.surpluscenter.com/item.asp?UID=2228012107004480&item=9-6557&catname=hydraulic

Looking at this as a possible motor. Seems to mathematically fit the bill .

https://www.surpluscenter.com/item.asp?UID=2228012107004480&item=9-7490&catname=hydraulic

Let me know what you think.

Thanks

 

[drankin]

The gerotor motor looks like it will work. The RPM range is there. Working pressure is a tad lower than ideal but I'd say it's a go.

The pump in the schematic is the symbol for a hydrostat (simplified). The Sunstrand that you picked out looks like a perfect fit. Make sure the counter-clockwise input rotation will work with the engine output. See if you can find the cut-sheet and/or manual for the pump.

I'll spec out the valves for you. I plan on designing the manifolds for the valves. Most will be cartridge valves. They are inexpensive and easy to maintain. "www.sunhydraulics.com"[/URL]

Because of the lower pressures we're working with, <3000 PSI, we can use aluminum body components. Brings the weight down.

Just let me know what symbols you have questions about.

I've come up with some ideas for dynamic hydraulic braking I'll include in the next schematic.

 

[RonL]

Its looking really good! One question. I have a Symbols chart here, but some of the symbols don't match exactly. Do you have a chart for the exact symbols you are using? I am attempting to put together a parts list as you add things to the schematic, and this would help me.

Also, as far as the schematic goes, this design uses a variable disp pump. What would be the implications of using an actual hydrostatic pump? Are they basically the same thing only with some of the circuitry built in? I was kind of looking at this pump as a possible candidate.

https://www.surpluscenter.com/item.asp?UID=2228012107004480&item=9-6557&catname=hydraulic

Looking at this as a possible motor. Seems to mathematically fit the bill .

https://www.surpluscenter.com/item.asp?UID=2228012107004480&item=9-7490&catname=hydraulic

Let me know what you think.

Thanks

I have used the surpluscenter for a lot of things and have never been dissapointed.

I would also like to pass this link on to you guys, find out if they have a store near you and if not, you might contact one and order the design manuals that most apply to what you are working on.
The manuals give good rule of thumb examples for calculating use of hydraulic, air and electric power design needs.

http://www.womack-machine.com/education/textbooks.aspx

Ron

 

[larkinja]

I have used the surpluscenter for a lot of things and have never been dissapointed.

I would also like to pass this link on to you guys, find out if they have a store near you and if not, you might contact one and order the design manuals that most apply to what you are working on.
The manuals give good rule of thumb examples for calculating use of hydraulic, air and electric power design needs.

http://www.womack-machine.com/education/textbooks.aspx

Ron

Thanks for the referal on surpluscenter, definitely good to know. Thanks for the education link. I had been looking at getting some books for general knowledge on the subject.

 

[larkinja]

The gerotor motor looks like it will work. The RPM range is there. Working pressure is a tad lower than ideal but I'd say it's a go.

The pump in the schematic is the symbol for a hydrostat (simplified). The Sunstrand that you picked out looks like a perfect fit. Make sure the counter-clockwise input rotation will work with the engine output. See if you can find the cut-sheet and/or manual for the pump.

I'll spec out the valves for you. I plan on designing the manifolds for the valves. Most will be cartridge valves. They are inexpensive and easy to maintain. "www.sunhydraulics.com"[/URL]

Because of the lower pressures we're working with, <3000 PSI, we can use aluminum body components. Brings the weight down.

Just let me know what symbols you have questions about.

I've come up with some ideas for dynamic hydraulic braking I'll include in the next schematic.[/QUOTE]

Just to make sure, the motors will be ok? I am thinking about ordering 1 for now just to do some test fitting with. We are in the process of finalizing the a-arm design, and figuring out the best way to couple the motor shaft to the cv axle, so I would like to have one of the motors in hand to do that with.

Helping us with the valves would be a huge help. Thank you! We had an idea that we are not sure if would be possible/practicle. Thought I would run it by you. I might have mentioned it before, but we are contimplating using a hydraulic steering cylinder to steer the front wheels. Could a single joystick control be used to control both the motors and a steering cylinder? The control would have to be able to steer while the forward and reverse control were in any position. Similar to a computer gaming joystick. Is this possible, at least without costing a lot?

CW rotation shouldn't be a problem. We are going to gear down the engine before going to the pump, so we can reverse rotation if needed.

What exactly do you mean by designing the manifolds?

Lastly, for the valves for free wheel, and hi-speed, will those be dc solonoid type? I would assume that would necessary for timing when switching modes.

The last question of the night is about the resevoir. Am I assuming right that this is still a open circuit? So some sort of tank will be required? How small can this be? Obviously space and weight is an issue. Just trying to figure out where this may need to go. Also, is it possible to do a closed loop, or does that complicate things?

Again, thanks so much for everything you are doing for us. You have no idea how much I appreciate it. We'll have to figure out some way to repay you for your efforts.

 

[drankin]

Just to make sure, the motors will be ok? I am thinking about ordering 1 for now just to do some test fitting with. We are in the process of finalizing the a-arm design, and figuring out the best way to couple the motor shaft to the cv axle, so I would like to have one of the motors in hand to do that with.

Helping us with the valves would be a huge help. Thank you! We had an idea that we are not sure if would be possible/practicle. Thought I would run it by you. I might have mentioned it before, but we are contimplating using a hydraulic steering cylinder to steer the front wheels. Could a single joystick control be used to control both the motors and a steering cylinder? The control would have to be able to steer while the forward and reverse control were in any position. Similar to a computer gaming joystick. Is this possible, at least without costing a lot?

CW rotation shouldn't be a problem. We are going to gear down the engine before going to the pump, so we can reverse rotation if needed.

What exactly do you mean by designing the manifolds?

Lastly, for the valves for free wheel, and hi-speed, will those be dc solonoid type? I would assume that would necessary for timing when switching modes.

The last question of the night is about the resevoir. Am I assuming right that this is still a open circuit? So some sort of tank will be required? How small can this be? Obviously space and weight is an issue. Just trying to figure out where this may need to go. Also, is it possible to do a closed loop, or does that complicate things?

Again, thanks so much for everything you are doing for us. You have no idea how much I appreciate it. We'll have to figure out some way to repay you for your efforts.

The motor looks like it should work fine.

Yep, a hydraulic pilot operated joystick will work in for you. They use these on hydraulic excavators. Look into picking one up at a heavy equipment dealership (Deere, Case-Linkbelt, etc.) parts department. Might be a bit spendy new so see if you can find one used.

Because the circuit is going to require a lot of valving we're going to need a manifold to pack all the cartridge valves in. Otherwise you end up with a bunch of individual valves that you have to hook together with tees/fittings/hose/tubes. It gets really ugly really quick. A single manifold can house several hydraulic circuits into a small package. I'll send you an example later.

All solenoid valves would be DC. Preferably 24VDC but we can go 12VDC.

Never intended this to be an open circuit. I think this would work best as a closed circuit. An air/oil cooler and small reservoir would be req'd.

As far as repayment, you could start by being a contributing member of PF (top, second to left button, "Upgrade"). I think it's around $15/yr. Post some pics so the rest of us here can follow your project.

 

[larkinja]

The motor looks like it should work fine.

Yep, a hydraulic pilot operated joystick will work in for you. They use these on hydraulic excavators. Look into picking one up at a heavy equipment dealership (Deere, Case-Linkbelt, etc.) parts department. Might be a bit spendy new so see if you can find one used.

Because the circuit is going to require a lot of valving we're going to need a manifold to pack all the cartridge valves in. Otherwise you end up with a bunch of individual valves that you have to hook together with tees/fittings/hose/tubes. It gets really ugly really quick. A single manifold can house several hydraulic circuits into a small package. I'll send you an example later.

All solenoid valves would be DC. Preferably 24VDC but we can go 12VDC.

Never intended this to be an open circuit. I think this would work best as a closed circuit. An air/oil cooler and small reservoir would be req'd.

As far as repayment, you could start by being a contributing member of PF (top, second to left button, "Upgrade"). I think it's around $15/yr. Post some pics so the rest of us here can follow your project.

Great, I will start looking for one of those. I would think it would have to fall in a particular gpm range correct? What values do you think I would be safe with? Seems the pump may be pushing close to 70gpm at times. Is there a particular kind that I would need that will work with both the motor circuits AND a steering cylinder?

Is there a disadvantage to using 12v vs 24v. The engine ignition and charging system, headlights, radios, etc. will all be 12v, so it would seem to make the most sense to use 12v, but if there is a big disadvantage, we can implement a 24v system as well, just complicates things a little, and adds another battery to the vehicle.

I am officially a contributing member now. :) I will get pics up soon. I intended to take some shots when I was out there Thursday (We work on these projects every Thursday), but I had not realized the battery in my camera had died, so I will get some soon, promise.

 

[drankin]

Great, I will start looking for one of those. I would think it would have to fall in a particular gpm range correct? What values do you think I would be safe with? Seems the pump may be pushing close to 70gpm at times. Is there a particular kind that I would need that will work with both the motor circuits AND a steering cylinder?

Is there a disadvantage to using 12v vs 24v. The engine ignition and charging system, headlights, radios, etc. will all be 12v, so it would seem to make the most sense to use 12v, but if there is a big disadvantage, we can implement a 24v system as well, just complicates things a little, and adds another battery to the vehicle.

I am officially a contributing member now. :) I will get pics up soon. I intended to take some shots when I was out there Thursday (We work on these projects every Thursday), but I had not realized the battery in my camera had died, so I will get some soon, promise.

Because the pilot operated joystick is used for piloting (signalling larger components/valves), it is a low flow component. It will drive the pump swash plate with the forward and reverse operation and the steering valve (that in turn drives the steering cylinder) with the right to left operation. It is basically four variable pressure reducing valves, one at 12, 3, 6, & 9 oclock. All it does is regulate pressure, the flow capacity is very low in the area of .25-.5 GPM max in the 0-500 PSI range.

12VDC is fine. I usually work with 24VDC components when working on mobile hydraulics. It's typical with mobile hydraulic equipment. The solenoid coils are smaller, wiring is gauge can be smaller, etc.

Welcome to contributor status!

 

[larkinja]

So would this be the type of componant?

https://www.surpluscenter.com/item.asp?UID=3524012417295912&item=9-7720&catname=hydraulic

or mor like this one?

https://www.surpluscenter.com/item.asp?UID=3524012417295912&item=9-6704-JS&catname=hydraulic

Then this would control 2 different valves? One for steering and one for the motors? I don't know if any of the valves on that site will work. The pump has a 12vdc solonoid on it. What does that do? Does that operate the swashplate, or something else?

 

[drankin]

So would this be the type of componant?

https://www.surpluscenter.com/item.asp?UID=3524012417295912&item=9-7720&catname=hydraulic

or mor like this one?

https://www.surpluscenter.com/item.asp?UID=3524012417295912&item=9-6704-JS&catname=hydraulic

Then this would control 2 different valves? One for steering and one for the motors? I don't know if any of the valves on that site will work. The pump has a 12vdc solonoid on it. What does that do? Does that operate the swashplate, or something else?

The first one, https://www.surpluscenter.com/item.asp?UID=3524012417295912&item=9-7720&catname=hydraulic, is the one you want. See the 4 buttons on top? That's the four reducing valves. GOOD PRICING.

I need more info on that pump, spec sheet. Don't know what the solenoid is for. I'm pretty sure we can hydraulically actuate that swashplate. A single joystick will control the pump and steering. The two buttons at 12 & 6 oclock control the pump and the 9 & 3 oclock control the steering. We need spec sheets for all these components so we can verify everything will work together.

 

[drankin]

Here is the spec sheet for that joystick. This shows the handle and buttons as well but I just need the hydraulic performance information. If you can find spec sheets like these for the other components it would help a lot.

 

[drankin]

Found out what that solenoid is for. EDC stands for Electronic Displacement Control. So the hydraulic joystick won't work for it as is. Depending on how the pump uses EDC we may be able to disable it and go direct hydraulic. Need more info though. Because Sunstrand is no longer around you might have to try a pump repair shop for info on that pump. I couldn't find anything with Google.

 

[larkinja]

Found out what that solenoid is for. EDC stands for Electronic Displacement Control. So the hydraulic joystick won't work for it as is. Depending on how the pump uses EDC we may be able to disable it and go direct hydraulic. Need more info though. Because Sunstrand is no longer around you might have to try a pump repair shop for info on that pump. I couldn't find anything with Google.

Ya, I'm having trouble finding info on the pump too. I'l keep digging to see what I can find.

 

[larkinja]

I called about a half dozen places today with no luck. The pump has been discontinued. One guy told me that parts were not available for it. Would this mean I should stay away from it? I'm worried that if we have to replace parts, we won't be able to get any. Do you know of any pumps that might work that aren't such a mystery that would be in the same price range?

 

[RonL]

I called about a half dozen places today with no luck. The pump has been discontinued. One guy told me that parts were not available for it. Would this mean I should stay away from it? I'm worried that if we have to replace parts, we won't be able to get any. Do you know of any pumps that might work that aren't such a mystery that would be in the same price range?

That is one problem with buying from surplus dealers, too often they bid on product lines that for one reason or another have been discontinued and most of the time repairs or replacment parts can't be found.
For expirmenting or one off design work its not anything to worry with and the prices can save a bit of money.
If the plan is to build a business and sell product, you have to find and use parts and suppliers that will be around to keep your business going.

Ron

 

[larkinja]

That is one problem with buying from surplus dealers, too often they bid on product lines that for one reason or another have been discontinued and most of the time repairs or replacment parts can't be found.
For expirmenting or one off design work its not anything to worry with and the prices can save a bit of money.
If the plan is to build a business and sell product, you have to find and use parts and suppliers that will be around to keep your business going.

Ron

I'm not after selling anything, I just want to make sure I don't spend $1100 and have to toss it in the scrap pile 3 months from now. I'm curious what the reference point is though? What would a similar pump cost that is current? If I can buy three of the $1100 ones for one of the current pums, then it is worth getting the old one. If it's a smaller difference or something, then I would go with a newer one.

Maybe I should go about it this way. What would a typical life of a pump like this be. Or how soon before it needs rebuilding? Because at that point it would be time for a new one since parts aren't available.

 

[drankin]

I'm not after selling anything, I just want to make sure I don't spend $1100 and have to toss it in the scrap pile 3 months from now. I'm curious what the reference point is though? What would a similar pump cost that is current? If I can buy three of the $1100 ones for one of the current pums, then it is worth getting the old one. If it's a smaller difference or something, then I would go with a newer one.

Maybe I should go about it this way. What would a typical life of a pump like this be. Or how soon before it needs rebuilding? Because at that point it would be time for a new one since parts aren't available.

Look into a newer one. Check with some fluid power houses in your area. Berensen or Hydrapower Systems are reputable. Usually they have some competent techs to help you out with your application. A good pump will last years if the system is designed well and it's not abuse.

 

[drankin]

Updated Schematic

Haven't gotten to the controls yet.

 

[larkinja]

Look into a newer one. Check with some fluid power houses in your area. Berensen or Hydrapower Systems are reputable. Usually they have some competent techs to help you out with your application. A good pump will last years if the system is designed well and it's not abuse.

You had said that the pump we were looking at was of good size. Do you think it is to big? Someone made a comment to me yesterday that the pump was to big for what I want to use it for. They mentioned that it could produce 300 peak hp. Since the engine driving the buggy is only around 200, am I oversizing the pump to much. The math says it is about right, I'm just wondering. If I am going to be looking at a more expensive pump, there is no reason to spend more than is necessary.

Thanks for any input you may have on this.

 

[larkinja]

Updated Schematic

Haven't gotten to the controls yet.

The schematic is looking good. I think I am following it :) For the manifolds, I take it when you said you will design it, that means once everything is set to go someone will manufacture the manifold for us based on your design?

Thanks again.

 

[drankin]

You had said that the pump we were looking at was of good size. Do you think it is to big? Someone made a comment to me yesterday that the pump was to big for what I want to use it for. They mentioned that it could produce 300 peak hp. Since the engine driving the buggy is only around 200, am I oversizing the pump to much. The math says it is about right, I'm just wondering. If I am going to be looking at a more expensive pump, there is no reason to spend more than is necessary.

Thanks for any input you may have on this.

It comes down to flow and pressure (and RPM range). You want 60-80 GPM @ 2500-3000 PSI. That's a HP requirement of 87-140 HP. That pump was a little big but the price was nice.

 

[drankin]

The schematic is looking good. I think I am following it :) For the manifolds, I take it when you said you will design it, that means once everything is set to go someone will manufacture the manifold for us based on your design?

Thanks again.

Yep, I plan on designing the manifold and drawings. I would suggest "www.hpsx.com"[/URL] to manufacture it. They've made dozens of manifolds for me over the years and have a top notch machine shop.

 

[larkinja]

Yep, I plan on designing the manifold and drawings. I would suggest "www.hpsx.com"[/URL] to manufacture it. They've made dozens of manifolds for me over the years and have a top notch machine shop.[/QUOTE]

Excellent. Any ballpark idea on what it costs to have that done?

 

[larkinja]

It comes down to flow and pressure (and RPM range). You want 60-80 GPM @ 2500-3000 PSI. That's a HP requirement of 87-140 HP. That pump was a little big but the price was nice.

What do you think our chances are of properly making the pump work without any additional data? A comparable pump locally is about $3800. We could buy three of the surplus pumps and still have money left over in comparison. Do you think we should think about trying it, or would that be opening a can of worms?

 

[drankin]

Excellent. Any ballpark idea on what it costs to have that done?

Maybe around $1000.