Project "Snow Drift"

[Oldskool 6,585]

Just now, Handy Don said:

With this power, I'd anticipate either more grunt at low speeds (pulling or climbing) or supporting a higher gear ratio (speedier)

Just looked at Hydro Gear's current offerings and their most powerful ZT drive can do "up to 300 lb-ft." -- not sure if that is peak or intermittent (but it's marketing so probably peak!)

 

 

Sorry, misread this. 

Yes, 125 continuous, 250 peak EACH. 500 to make the machine break inertia and "stiction" and move.

 

Know anyone with a blown-engine, rusted out deck, flat tired, high-end ZT that can be a new donor?

I dont but I've been looking at hydraulics.

[Handy Don 10,702]

Horsepower = torque in ft. lbs. x rpm ÷ 5,252

 

What you have (estimated): 160 rpms and 125 ft-lbs = 3.8 HP (right where we were guessing)

 

The Chief: 600 rpm and 2124 torque = 242 hp (this is nonsensical so the torque value must be inch-pounds)

so 600 and (2124 ÷ 12) = 21 hp (yes, this makes more sense)

 

This would be PER SIDE, so probably more motor than you need.

 

Seems like you need about 10 hp per side and you also want bi-directional motors (you do what to go backward sometimes )

What RPM do you need at the screws? 

What range of ratio can you accommodate from drive to screw?

That'll give us what we need to seek out motors that would work. From there we can see what pump will be needed.

 

[DennisThornton 4,769]

44 minutes ago, Oldskool said:

Interesting. I think I had read somewhere earlier in the build that these were 15:1 but maybe not. Not having exact numbers it's hard to calculate. Somehow I have to get a baseline rpm and torque output to move further.

Maybe I'm getting confused.  Nope!  I'm getting confused with ft/lbs vs lb-in

 

figured that each drive was supplying about 125 ftlb at the output shaft

vs

Torque, Output

• Continuous - 14 Nm [120 lb-in]
• Intermittent - 20 Nm [180 lb-in]
• Peak - 27 Nm [240 lb-in]

[Oldskool 6,585]

23 minutes ago, Handy Don said:

Horsepower = torque in ft. lbs. x rpm ÷ 5,252

 

What you have (estimated): 160 rpms and 125 ft-lbs = 3.8 HP (right where we were guessing)

 

The Chief: 600 rpm and 2124 torque = 242 hp (this is nonsensical so the torque value must be inch-pounds)

so 600 and (2124 ÷ 12) = 21 hp (yes, this makes more sense)

 

This would be PER SIDE, so probably more motor than you need.

 

Seems like you need about 10 hp per side and you also want bi-directional motors (you do what to go backward sometimes )

What RPM do you need at the screws? 

What range of ratio can you accommodate from drive to screw?

That'll give us what we need to seek out motors that would work. From there we can see what pump will be needed.

 

I was thinking that may be inch pounds. It seemed high for ftlbs.

 

I can go up to a 30 tooth on the drive but I kinda have to stay with the 40 tooth on the screw.

[Oldskool 6,585]

If the 2124inlbs converts to 177ftlbs and the rpms are more then triple  even with the gear ratio I have now wouldnt it go a bit more then 3 times as fast?

[Handy Don 10,702]

1 minute ago, Oldskool said:

I was thinking that may be inch pounds. It seemed high for ftlbs.

 

I can go up to a 30 tooth on the drive but I kinda have to stay with the 40 tooth on the screw.

Ok so I'm building a Google sheet for you.

I'll figure 15-30 in 5-tooth increments for the drive.

I'm assuming 10 or 12 hp per side required

What RPM do we need on the screws to get the speed you're looking for? Or, alternately, what is the forward distance per turn and desired speed and I'll have the sheet calc the rest?

[Tractorhead 8,620]

15 minutes ago, Handy Don said:

what is the forward distance per turn 

 

Think that and the wished speed give a good base to calculate the required rpm a little more.

i asked allready, but i see no answer for now or i maybe missed it

[Oldskool 6,585]

36 minutes ago, Tractorhead said:

 

Think that and the wished speed give a good base to calculate the required rpm a little more.

i asked allready, but i see no answer for now or i maybe missed it

Sorry if I missed that. It's been hectic today.

 

[Oldskool 6,585]

The screws are loosely based on the original tire.

Not including slippage  50in of travel per rev of screw would be a good starting point for me.

 

[Tractorhead 8,620]

48 minutes ago, Oldskool said:

Sorry if I missed that. It's been hectic today.

 

No problem 👍

[Wheel Horse 3D 3,646]

Love this project and all the math thrown at it! I keep wanting to pitch a thought in, but ya'll got it covered lol!

Edited February 20, 2021 by Wheel Horse 3D

[Oldskool 6,585]

3 hours ago, Wheel Horse 3D said:

Love this project and all the math thrown at it! I keep wanting to pitch a thought in, but ya'll got it covered lol!

Thank you. Toss something in. Every bit helps.

[8ntruck 6,445]

13 hours ago, Wheel Horse 3D said:

Love this project and all the math thrown at it! I keep wanting to pitch a thought in, but ya'll got it covered lol!

I was thinking about this while walking the dog, thinking about starting with the desired screw speed and working backwards from there.  Handy Don went down the same road I was going to and beat me to press with it.

 

Oldschool - this has an 18 horse motor, right?  Figuring about a 1 horse loss through each drive, that leaves 8 horse pre side to drive with. 

 

[DennisThornton 4,769]

I just can't imagine that there isn't more than enough HP.

[Pullstart 59,957]

I don’t know about all the figures.  What I do know, is AWESOME WORK!

[Oldskool 6,585]

1 hour ago, 8ntruck said:

I was thinking about this while walking the dog, thinking about starting with the desired screw speed and working backwards from there.  Handy Don went down the same road I was going to and beat me to press with it.

 

Oldschool - this has an 18 horse motor, right?  Figuring about a 1 horse loss through each drive, that leaves 8 horse pre side to drive with. 

 

Yes it does have 18hp.

[Oldskool 6,585]

I think its enough HP. It's the drive units themselves.

[Handy Don 10,702]

 

1 hour ago, 8ntruck said:

thinking about starting with the desired screw speed and working backwards from there.  Handy Don went down the same road I was going to and beat me to press with it.

 

 

Yesterday I put together a Google sheet showing the current situation (using the Hydro Gear specs) and why the existing units won't do what we were all hoping to do (need a lot more RPMs at the current torque or a lot more torque at the current RPMs). Not gonna get there from here. (Yes! I get to use a famous "down east" saying!)

 

Added to the sheet a separate grid with goals for speed and possible final drive gearing to see what RPMs and torque those would call for (per side). That led me to researching reversible hydro motors that met that spec, assuming 10 or 12 HP available to each side (to account for asymmetric operation while turning).

 

If all that is good for @Oldskool and he wants to move ahead, we'll look at a pump that can supply the motors and then controls

 

Edited February 20, 2021 by Handy Don

[Handy Don 10,702]

One trick to this is that ZT hydros are unitized--variable output pump, fixed output motor, reservoir, and relief/check valves all in one.

To use a single pump for two motors requires two relief valves to make sure there is always full pressure for the other motor even if one motor's control is in bypass (neutral). Like water, oil will follow the path of least resistance!

 

[wallfish 15,981]

Pump output to a flow divider then to 2 independent control valves. The pump and flow divider would have to have double the GPM capacity to handle both motors full open.

Lots of options and stuff here to look at. Prices aren't too bad but hydraulics can get expensive when it all adds up.

  https://www.surpluscenter.com/Hydraulics/  

 

 

[Oldskool 6,585]

2 minutes ago, wallfish said:

Pump output to a flow divider then to 2 independent control valves. The pump and flow divider would have to have double the GPM capacity to handle both motors full open.

Lots of options and stuff here to look at. Prices aren't too bad but hydraulics can get expensive when it all adds up.

  https://www.surpluscenter.com/Hydraulics/  

 

 

I think it's going to be the  direction I'm headed. I have a catalog from them. That's where my sprockets came from.

[8ntruck 6,445]

I think a pressure compensated variable pump, fixed volume motors, and variable control valves would work.  Not sure you need a flow splitter.  Should be able to do that with plumbing.

 

The pump would need to be big enough to run both motors full out.  The pressure compensated pump is a variable displacement pump that uses pressure feedback from the system to increase pump displacement when pressure falls and decrease pump displacement when pressure rises. 

 

With a system like this, you need to size the plumbing between the pump and motors to minimize pressure drop at the motors.  Lower pressure for a hydraulic motor means less torque.

[Handy Don 10,702]

3 hours ago, wallfish said:

Pump output to a flow divider then to 2 independent control valves. The pump and flow divider would have to have double the GPM capacity to handle both motors full open.

Lots of options and stuff here to look at. Prices aren't too bad but hydraulics can get expensive when it all adds up.

  https://www.surpluscenter.com/Hydraulics/  

 

 

At least double the GPM and while maintaining adequate pressure. I'd try to size the pump at 110 or even 115% of the calculated motor loads at their continuous output ratings to account for starting and accelerating and hills! And up the motors and pump even more if there're thoughts of higher speeds (I used 10mph in my spreadsheet but that may be too slow for some folks!) or towing. Those values can be adjusted in the worksheet that he has.

But I did work the numbers keeping within the 18hp power budget--getting too much pump will be wasted unless a bigger engine was planned!

Of course, once you've got a pump, you may want to add other hydraulic gadgets!

Edited February 21, 2021 by Handy Don

[Wheel Horse 3D 3,646]

My only 2 thoughts are, maximum surface area to the ground,(minimize ground psi)

And ideal pitch for screw to balance ground torque against screw, vs forward momentum should be 45 degrees. A steeper pitch, while increasing forward thrust per rev, increases forces acting perpenndicular against the screw.

A lesser pitch looses forward momentum, but decreases that opposing torque.

[Tractorhead 8,620]

Another thing i found out when i searched a fitting hydraulic motor for my Sicklebar hedgecutter project,

the bigger the motor‘s the slower their output RPM.

 

when i do my equations, to estimate what i need on torque i use a torquewrend to get a feeling of what 

torque i will need estimated to work that thing.

therefore i get a 2 cm thick piece of woof i try to cut.

 

 

with the torquewrench on the sicklebar i try to find out, how much torque shall be enough to cut that.

after i got my value i double the result + adding 10%reserve for any unknown i may overseen.

 

On a sidenote:

That thing works like a charm and Hedgecutting is now a just act of Fun and Seattime instead before.

 

 

Because of the needed flow on the pump i would calculate both motors on max flow (peak) 

i like the idea of the flow divider. But that also consumpts a bit of the given input force.

i found on my search, that there exists a dual steering valve for such purposes but i missed the link.

This valvesystem with integrated divider wasn‘t much more expensive than a normal dual valve.

will do a research,i hope i find the source again.

Edited February 21, 2021 by Tractorhead