OutdoorKing Repair Forum Forums Restoring, Customising and Modifying Unusual Customisation Projects ZTR-X1

G'day Folks,

With the most recent testing having been completed, Lockheed Martin and the other development stakeholders announce development thus far of the ZTR-X1.

Seriously, I reckon I'm ready to show you what I've been playing with off and on for the past couple of years. Work as been slow because of available time.It's still basically still a proof of concept mockup.

The story goes back to....well, before 2015 at least. Started with standing in the shed looking at the drive of my Greenie with ale in hand and a good few under the belt. . Why couldn't a zero turn be based on two greenfield drives?!

Treasury permitted limited funds to be spent on a modest collection of old Greenies as donors. Ah, I hear you say, that's why he's got all those bits and a disturbingly detailed knowledge of these machines.

Initially a vertical engine was investigated but dropped due to the difficulty (impossibility?) of getting the belt runs while maintaining balance and ground clearance. Although it looks like it was cobbled up in an afternoon, it took hours of CAD sketching and days of drawing full size mock ups of the belt runs and component clearance and position details. It was tough (!) to get the belt runs, engine placement, tensioner setup, etc. designs has allowed for cutter belt placement. Rework of the drives and axles also took a bit. Couldn't have done it without the lathe I got last year.

Clearance or the pullies and belts etc at the back are assuming clearance for a 30 degree incline which is the Australian Standard for longitudinal stability.

All intentions were to complete it to 'grass cutting' status but I was getting bogged down with the cutter deck mounting and clutch design and realised that while it would work in theory, I still didn't know how 'driveable' it would be. I.e. I was concerned it would be twitchy. To that end it has been finished to proof of concept with little attention to niceties. The front end is purely a mockup.

The G65 is the only horizontal shaft engine I have so it's the test engine. When it's at grass cutting stage I can go to the treasurer for funds for a new engine.

First run was last weekend. Initial suspicions were right! It was twitchy! Reminded me of some horses I've ridden!

I've just given it another run with spring bungees in the pedal linkages. It's much better! Need to mess around with spring stiffness a bit and maybe the engine pulley size cause it's a bit fast. Also, I'm keen to get the weight of the deck on it to calm the front end a bit. Basically balance is good.

Work will continue.

Cheers

P.S. Guards etc will be fitted. I'd also do a video but I'm struggling with file size.

Now That is not something you see every day!

Believe it or not I have had the idea for exactly this floating around in my head for Years! I just never fount the time or a couple spare greenfield to make it happen..
Very cool that you've made it compact & based on a standard chassis. I was always worried that it would end up all very bulky.

So looks like you're using foot pedals, have you considered hand levers in the conventional ztr fashion? I know foot pedals are keeping with the Greenfield theme, but I suspect it would take some getting used to. I would possibly try a set of dampers off a Hustler, the more resistance on you're pedals the smoother you will get it.

To top it off you need to find one of the very rare 1000mm double spindle greenfield decks!

A Vanguard V Twin on the back would look and sound the part I reckon..

Cant wait to see more!

G'day nath,

Compact was something I worked very hard on. It was initially designed to be 28" wide ( to suit a 28" deck). The frame widens by 50 mm at the back to accomodate the drives. I also offset the drives to keep it narrow and for other clearance issues.

I did consider levers in the beginning but opted for pedals for a few reasons:
Easier to design and build.
The weight of levers would have to be carefully balanced so they didn't overcome the springs in the clutch packs. The springs in the clutches could be strengthened but I figured that the pedals were an easier option.
I'm used to driving machines with pedals so didn't figure I'd find it too foreign.

I've since acquired a 32" deck which if great! The situation is that this place has a lot of wide open grass to cut but also a lot of tightly spaced trees that I need to get around so to be honest 32" is probably ideal.

I popped the deck on this afternoon and that's helped heaps. Having some weight up the front has settled it down quite a bit. Basically it's quite driveable now. I'll muck about with fine tuning a bit and do some more testing but basically I think it's ok. Also, to be honest, I'm probably just getting used to it too.

Cheers,

Hey prd

That makes sense with the extra weight, even hydro ztr's are a handfull without the deck under them

Any idea what you are going to do up front panel wise? kind of a shame the engine is out back when it would probably have fitted where it normally would go.. Damn Belts!

I'll be on the lookout now for a couple of cheap frames!

Excellent work prd, I will bite how did you split the rear drive

G'day prd, nath and Norm
This is one to follow for sure. I love clever custom projects.
I understand the sensitivity and all - I mean Lockheed Martin!

I think ZTR and Greenfield drive belong together, and I don't know why
Theo never went down that garden path.

The first ZTRs were friction drive and date to about 1969.
I have fond memories of the first ZTRs sold here - a USA Dixon, c1980 (I think).

All the best with the ZTR-X1 project.

-------------------------------
Jack

It going to be obvious that I don't know anything about the Greenfield drive.

This setup to looks to be a nightmare to repair but that depends to reliability the drives. Also how system does achieves anytime reverse of the drive wheels independently of each with the simply change of the pedal motion from forward to reverse. Basically how does it keeps from destroying the fiction drives when going from full forward to full reverse in a split second. Here on ZTR with hydrostatics I can literately go from full forward to spinning the drive tires in reverse in a single motion.

I think this why most manufactures have gone hydrostatic drives as they are highly reliable, reverses on the fly, and only use one drive belt to drive either a single pump and multiple pumps with wheel motors or two independent hydro static transaxles.

As in most cases that will depend on the operator. The standard greenfield mowers have the same issue, if you are jamming them in full forward full reverse all the time you will kill the corks. In saying that, I do the house yard with a Hustler fastrak, as a general rule I dont hit reverse much with the levers, it tends to rip the grass up. The other thing though is with the greenfield drive there is no built in braking when you let off like a hydro, you have to touch reverse to slow/stop. In saying that, if you are kind to them they are a very robust drive system and can last a very long time.

In principal it is the same concept as the early Dixon friction drive

Ultimately I don't think production is what prd has in mind, just a very cool exercise to see if it can be done

Morning Folks

Nath, I did cosider putting the engine mid ship because I thought it might make the belt runs easier but weight on the front end becomes a problem. I even considered shifting the drivers position aft to counteract this but decided to go with the engine and driver position recipe used on almost all ZTR's. Front cowling will be completely new. Fortunately I have access to a guillotine and folder.

Norm, it's very literally two drives and two axles. Imagine bolting two frames together side by side having first cut th inner wheel off each. That's the principle. ..........and I did mess with the idea of doing just that but the machine would be very wide indeed!

Jack, I was very fortunate to get the the backing of Lockheed Martin. It means we have a foot in the door with the Mars manned flight project. .
I wondered many times, rather nervously why Greenfield had never done it. I say nervously because perhaps they did I try it and abandoned it for some reason that I would only discover after putting in all this effort. Who knows, that might still happen!
I didn't know that Dixon had used friction drive also.

AVB, you raise a couple of good points.
Access for maintenance is not as hard as it looks. I worked hard to make it easy to get the clutches in and out and accesss the tensioners etc.
I like simple elegant engineering and am annoyed that the back end looks like a rats nest but it's impossible for so much stuff to be in such a small space and not have it look that way.
The greenfield drive allows instant forward/reverse changes. Every kid who's ever driven one has put marks up and down the back yard trying to spin the wheels by charging forward and then stomping on the reverse. .
Drive clutch plate reliability is something I've thought a lot about. A normal Greenfield being manoeuvred in and out amongst trees and shrubs for example is subject to a lot of direction changes and clutch slippage and in my own case I've only just replaced the corks for the first time on my own daily drive after 34 years!
Increased cork wear is inevitable but given how long it lasts on a normal machine I think it'll be ok. That said, this is an experiment and working all this stuff out comes with the territory.

Cheers,

prd, I must admit my head is hurting regarding this drive, because at this stage I am unable to really get my head around how it is working.To obtain this zero turn are you able to stop one wheel (or even have one going forward and the other in reverse?) as I said my head is hurting

It's really simple, there are 2 complete drive assemblies, one for the left wheel, one for the right. The wheels aren't connected to each other in any way. So at any given time either wheel can be going either way. Think of it as 2 machines side by side but with only one wheel on each.

Prd, I wish every engineer would think about the ease service ability. Good for you for thinking along these lines.

Some the riders I service can be a real problem to service. I just replace the steering shaft on a Cub Cadet LT1042. It took me 3-1/2 hours to do it as you got half disassembly frame. Remove the rear fender pan and the operator tower just get the shaft out and back in. If the engineer was thinking of the ones that must service later they could made it a 15 minutes like many other mowers that I change these shaft out on.

Sometimes I would like to find the penny pincher that decided the hex head bolts are just as good carriage bolts under these fender pans too. Strange the square is still there but using the hex head bolt makes it necessary remove the pan just to get a wrench on the head.

Prd if only you had got together with Lou a year or so ago you may have helped prevent Greenfield from going bust. Their machines were the best built small rider but the turning circle was always a problem and with them being able to build a zero turn without huge manufacturing changes then it might have just saved the day. I take my hat off to you for this.
AVB I'm with you on some of those bolts/nuts you can only get to from one side, easy on an assembly line but hell later when you need to do maintenance

well done sir! the heart is happiest when the head and hands work together,thank you for sharing

G'day gml,


Im sure that's a very old truism and I'm sure I'm old enough to have heard it before but I haven't. And it's spot on! Absolutely spot on!

It completely explains what I did and why I did it.

A less enlightened person would say, 'If you wanted a ZTR, why didn't you just buy one' which completely misses the point!

That one goes on the office wall tomorrow!

Cheers