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Author Topic: What are the limitations of z-drives?  (Read 3805 times)

RipSlider

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What are the limitations of z-drives?
« on: June 04, 2008, 12:45:28 pm »

Hello all.

I was just wondering if there is a reason why z-drives are not more commonly used? They seem to be quite an efficient way of propulsion - all the force goes directly backwards - and also you can turn it to any angle you like.

I was thinking that the issue would be that there are two gear systems in the system, but a lot of cars have this, and they seem to do OK.

Is there an issue with performance, maintainance etc?

I'm referencing both model- and full sized - ships here.

Thanks very much

Steve
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grasshopper

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Re: What are the limitations of z-drives?
« Reply #1 on: June 04, 2008, 12:57:31 pm »

I've had a play with the Graupner z drives - there is a flex drive and then two sets of gears - and the usual thing with these is power loss throught the gears and they don't like reverse!

They look good though and if can supposedly handle a 700 size motor - but then without chopping it about you're restriced in prop diameter.
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Martin (Admin)

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Re: What are the limitations of z-drives?
« Reply #2 on: June 04, 2008, 01:05:56 pm »


From the modellers I've spoken too, high wear and maintenance,
noisy and tend to eat quite a bit of engine power.  :-\

There's a nice on on ebay at the moment! - http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&rd=1&item=180248603606&ssPageName=STRK:MEWA:IT&ih=008
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towboatjoe

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Re: What are the limitations of z-drives?
« Reply #3 on: June 04, 2008, 03:03:32 pm »

Martin, is that a z-drive or an outdrive in the photo? :-\
Looks to me like it mounts on the transon instead of underneath.
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Martin (Admin)

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Re: What are the limitations of z-drives?
« Reply #4 on: June 04, 2008, 03:17:25 pm »

Isn't an out-drive a z-drive then?  :embarrassed:
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towboatjoe

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Re: What are the limitations of z-drives?
« Reply #5 on: June 04, 2008, 03:28:31 pm »

From what i understand a z-drive can rotate 360 degree and an outdrive is the outer unit on an inboard/outboard boat. Jet drives have outdrive units as well which is limited in their turning radius.

I've been debating on going to the expense of installing z-drives on my at/b, but from the info I gathered here I may just go with straight shafts. I'm building this one for me so changing the arrangement wouldn't matter.

Always find a lot of interesting reading here. Glad to be part of Mayhem.
Keep the posts coming!
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catengineman

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Re: What are the limitations of z-drives?
« Reply #6 on: June 04, 2008, 05:02:13 pm »

I think what you refer to as Z drive are Graupners ASD units or shottle drives, the sort that are used on Tito Neri and Garth tugs.

The only problem I have found on the model side is control of the 360 revolution but it has been done by other modelers with laptop control (I think) as for the real thing no real big problems and the idea is employed on some big vessels "PODS" have the same idea 360 control.

Harbour tugs seem to err on the VS drive system which is easier to operate and slightly more versatile

IMHO

R,
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DickyD

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Re: What are the limitations of z-drives?
« Reply #7 on: June 04, 2008, 05:06:31 pm »

This is an English/American thing  towboatjoe over here we call them Z drives because of the way the drive shafts go when engine and outdrive are mounted on the transom (Z) if you see what I mean. O0
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towboatjoe

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Re: What are the limitations of z-drives?
« Reply #8 on: June 04, 2008, 06:37:06 pm »

This is an English/American thing  towboatjoe over here we call them Z drives because of the way the drive shafts go when engine and outdrive are mounted on the transom (Z) if you see what I mean. O0


Yep I see what you mean. I've got brochures from manufacturers of the "shottel" drives and they refer to them as z-drives here. Just like the transom mount units they also go out the gearbox, 90 degree down, and 90 degree out to wheel. So I guess they're all really z-drives, huh!
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banjo

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Re: What are the limitations of z-drives?
« Reply #9 on: June 04, 2008, 08:58:18 pm »

 O0
I have "Z" or "schottle" drives on my Tito Neri.

The mk 1 units had a problem with the gears stripping when over driven by 900 series Graupner motors.

The gears are now made of sintered bronze and accept the 900 series power without problem.

Their use is a matter of expense.   The units cost an arm and a leg, 900 series motors are not cheap either.   The servo has also got to be a top class high performance jobby as well, to move the unit against the thrust of the prop sometimes. 

Users in the USA, reported failures in some of the unit structure, but I have had no problem there; I think it was one of those self perpetuating faults, technical experts solving a problem that didn't exist.

They really do do what it says on the tin, nothing else like them; that is if you need them.

BTW a Futaba/Robbe F14 Navy twin stick is a must to get the full benefit, especially if you fit an extra twin stick on the right hand side!!

See what I mean about the money!!
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catengineman

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Re: What are the limitations of z-drives?
« Reply #10 on: June 04, 2008, 09:05:08 pm »

Same for me and my Tito, though I did go down the route of modified servos to get 360 deg rotation on the drive's (as in real life) but had the problem of where the drive was when I let the stick go. The only way to tell was to drive and that gave some very strange movements of the tug, so it was back to the std servo ops and fwd rev operation on the drive motors.
Other than that trully a fantastic drive system

R,
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banjo

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Re: What are the limitations of z-drives?
« Reply #11 on: June 04, 2008, 09:13:56 pm »

The only problem I have found on the model side is control of the 360 revolution but it has been done by other modelers with laptop control (I think)

I have computer control on my Tito.
It was an experiment thrust upon me by my son, he had a car computer loafing about spare that fitted into the Tito hull and the thing snowballed.
I have almost 360 control, and a panel on the laptop shows the angle of thrust.
Its an adventure operating the whole system; not to be undertaken on a busy pond!   Anticipation is the key  ;D
I now know how Tanker skippers feel when faced with the inevitable!!

BUT its a magic bit of kit & if I can get it all to work at once then who knows  where it could take me!!!!!!!!!!!!!!!!!!!!
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RipSlider

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Re: What are the limitations of z-drives?
« Reply #12 on: June 06, 2008, 02:31:19 pm »

hmmm.... confused.

If your using the z-drive as a PODS system, what is the need for a computer to control?



Thanks for all your responses chaps.  - Does anyone have any metrics on how much energy loss comes from a z-drive?

I was thinking of using one on a racing boat - I can't see that there will be much more loss in a liberally doped z-drive system, to a long flxi-drive system, but then again I'm a very clever chap.

Steve
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