hurth / zf input rotation direction?

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guyd

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Minehead
bossingtonhall.co.uk
how do i tell which direction a smaller (hbw100 150 etc) zf or hurth gearbox is set to? they are available in both rh and lh (clockwise or anticlockwise) and i know from past experience that i need the right version.... i need a clockwise as looking fwd from the stern whereas most are anti.... mine works, but sounds horrible and im anticipating a replacement soon....and i can find plenty on ebay etc but with no direction information its an expensive gamble.

my engine is a lister SR2.
 
Surely they will reveal the rotation if asked? Though if they haven't revealed that in their advertisement on eBay it is a bit of a worry. (would they know?)
 
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They can be operated in either direction - ie with left or right handed prop, but the reduction ratios may differ and the torque rating is slightly different. Normally ahead (gear lever moved forward) requires a right hand prop.

My ZF10 was running in 'reverse' with a left hand prop when I bought the boat and had been with no problems for years. (When I discovered this, it did explain the whine from it)
 
input, not output direction, but thanks.

most sellers dont seem to know. i would have thought that the serial number might be 'a' and 'c' or something, or L and R.... But i have yet to see any documentation to tell me.

if you put a lh on a rh engine, it just about turns the prop but you can stop it with your hand.
 
guyd said:
how do i tell which direction a smaller (hbw100 150 etc) zf or hurth gearbox is set to? they are available in both rh and lh (clockwise or anticlockwise) and i know from past experience that i need the right version.... i need a clockwise as looking fwd from the stern whereas most are anti.... mine works, but sounds horrible and im anticipating a replacement soon....and i can find plenty on ebay etc but with no direction information its an expensive gamble.

my engine is a lister SR2.
Click to expand...

So the Lister turns the opposite way to most engines?
 
annoyinginly, yes. looking forward, from the transom, it turns clockwise. So the input shaft, as lookingat the gearbox input shaft from the bow, turns anticlockwise.

edit. just double checked with a photo of the engine. picture shows an arrow going clockwise on the casing. ignore statement above.
 
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guyd said:
annoyinginly, yes. looking forward, from the transom, it turns clockwise. So the input shaft, as lookingat the gearbox input shaft from the bow, turns anticlockwise.

edit. just double checked with a photo of the engine. picture shows an arrow going clockwise on the casing. ignore statement above.
Click to expand...
The standard rotation of the ZF10 according to my manual/data sheets is RH - clockwise engine rotation / clockwise input shaft looking at it towards the stern.

LH input rotation version is a special option at extra cost apparently.
 
guyd said:
input, not output direction, but thanks.

most sellers dont seem to know. i would have thought that the serial number might be 'a' and 'c' or something, or L and R.... But i have yet to see any documentation to tell me.

if you put a lh on a rh engine, it just about turns the prop but you can stop it with your hand.
Click to expand...
 
Don't know if this thread is still "live" but here goes...

Please note, to avoid confusion, all directions of rotation mentioned below are given looking aft in the boat. ie looking at the free end of the engine.

I have what I think is a ZF-Hurth MS12 which came to me fitted on the back of a "new" Volvo Penta and I have the same problem in that the input from the (clockwise) engine is not correct for the gearbox, which requires an anti-clockwise input for the servo-mechanical clutch mechanism in the gearbox to function.

I've had all the assertions that changing the prop or inverting the control lever will do the trick, even from some very experienced people, but they clearly don't understand the functioning of the gearbox.

It would seem that you may have what I need and I may have what you need. Looking at the literature and with the knowledge that the majority of marine engines are clockwise rotators that would make mine somewhat rare.

If you still have the problem (or the old gearbox) perhaps we could do a swap/trade, assuming that the splines, couplings etc. are compatible.
 
Gearbox input shafts normally match the engine rotation which is always clockwise look aft from the front of the engine. I have yet to come across an engine which rotates in the opposite direction which is the only time you'd need a gearbox that requires anticlockwise input shaft rotation.

Have you tried the engine with the MS12 gearbox and had no drive?
 
It used to be quite common to have "handed" engines for marine applications. Mostly on larger diesels and admittedly less common now, but they do still exist.
I have opened up the gearbox (MS12) and there is no doubt that it only operates one way. Not easy to find, but buried in the ZF literature there is a mention of "handed" gearboxes, presumably a rarity and by special order no doubt, but I just happen to have inherited one! I'll find the reference and post it here when I have time.
When fitted, and with the engine running the shaft will turn ahead and astern when selected, but hop down into the engine room and hold the shaft and you can stop it easily, no matter how high the engine is revving.
The wee balls that travel in tapered slots to wedge the clutches in engagement are oriented in the wrong direction for a RH engine.
 
1. Description
1.1 Brief description
ZF-HURTH Marine boat reversing gearbox units of the ZF M line are servo-automatically controlled helical gear transmissions developed for use in pleasure craft and commercial craft. The servooperated multiple-disc clutch requires only minimum effort for shifting, making the ZF M transmission suitable for single-lever remote control via a rod linkage or shift cable.
In emergency situations the ZF M permits direct reversing at engine speed above idle rpm.
The torque capacity of the clutch is exactly rated, preventing shock loads from exceeding a predetermined value to ensure maximum protection of the engine and thus providing the effect of a safety clutch.
The transmission units are characterized by low weight and small overall dimensions. The gearbox castings are made of a high-strength, corrosion-resistant aluminium alloy, chromized for improved seawater resistance and optimum adhesion of paint.
A choice of gear ratios, a high efficiency rating and low-noise operation are other prominent features of the ZF M gearbox units.
The transmissions are immersion-lubricated. Maintenance is restricted to oil level checks (see «Maintenance», chapter 4).
The shafts are supported by heavy-duty taper roller bearings and the gearbox is designed to take the axial propeller thrust (for permissible values see «Technical data», item 1.2).
Transmission sizes are available for right-hand (RH) and left-hand (LH) rotation of the input shaft, the direction of rotation being specified as seen by an observer facing the input shaft. In gear lever positions A, the engine shaft and the propeller shaft rotate in opposite directions, in position B in the same direction (Fig. 1). On model ZF 15 MIV, the directions of rotation are the other way round (Fig. 2).
Engine manufacturers should note that the direction of rotation refers to an observer facing the flywheel, so that lefthand rotation of the engine corresponds to right-hand rotation of the gearbox input shaft.
 
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