[TowerTalk] Brake Winches

Tue Jun 30 04:15:56 EDT 2015

Having used winches and worm gear/worm gear wheels in industry, and in 
ham radio for over 50 years I can only go by experience which shows far 
less effort to raise a given load using a good worm gear winch.  Yes, 
the worm gear has far more contact area between the worm gear driver and 
the worm gear wheel which would reduce the efficiency.  I have not seen 
any really good worm gear to worm gear wheels used in the ham world for 
raising towers including my Dayton.  Although it certainly makes raising 
the 1300# LM470 far easier.  The winch sees a far greater load than the 
1300#, but I've not measured the dimensions, or angle to calculate the 
loads.  It's just a 50:1 worm gear is far easier to use raising that 
1800# tower compared to a 15 or 20:1 spur gear.

A good worm gear to worm gear wheel has a finely machined and/or lapped 
interface that is polished.  The area of contact is sliding as it is in 
spur gears, but that area is far greater in the worm gear to worm gear 
wheel and 90 degrees to the movement of the driven gear.  Compare a 
precision worm gear to worm gear wheel (polished steel worm gear to 
brass worm gear wheel)   to those in the winches we use  Stamped steel 
on steel with a minimum of machining.  Without going into the 
manufacturing steps, the stamped gears are much less expensive to make.

I disagree with two points in the article.  You can reverse direction on 
a loaded worm gear/worm gear wheel and a high viscosity grease is no 
longer needed to lubricate the gear interfaces. Greases like BR2 are 
very slippery and of a viscosity used in standard grease guns like 
Alemite .  It's not clear, but he may be referring to the self breaking 
action, but depending on load, the worm gear can run under load in 
either direction. The friction varies greatly depending on the size of 
the gears and the load applied.  Large gears with heavy loads do indeed 
have substantial friction.

"Used to be"(I worked in maintenance for 26 years before earning a 
degree in CS), we used a black, thick, and gooey grease affectionately 
known as bear grease, or "similar" names. Get a little on your hands and 
you'd look like you had bathed in it by the time you got back to the 
shop and it was very difficult to wash off.  We used it on small worm 
gears and 45 degree beveled gears. Mainly it was used (in our operation) 
to prevent vibration, or mechanical resonance in sensitive areas.

Other than the vibration issue, we switched to the BR2 grease for 
reduced friction.

One shortcoming of the stamped, steel on steel gears, is they are often 
assembled with excess pressure between the worm gear and worm gear wheel 
and depend on the gears "wearing in". Winches using this approach can 
require a lot of effort to use with a notable reduction in effort over 
the first few hours of use.   (hours of use on a winch?)

In a more crude gear system, like the winches which use steel on steel 
rather than steel on brass, where they depend on wear to get the proper 
mating surfaces I'd like to try the proper mating of the gear 
interfaces.  If I had the time, money, and two working hands, I'd like 
to try lapping the crude gears with ever finer grades of lapping 
compounds until they give a proper, smooth, interface and use a good 
grease meant for a high pressure mating surface as in these winches. 
Lapping gears has a steep learning curve with a fine line between too 
much and too little.

One change I'd make would be to add zerks to the worm gear bearings so 
they could be properly lubricated.

Mating surface match, mating area, smoothness, and lubrication are 
crucial to the proper operation of the worm gear and worm gear wheel 
with minimum drag.

Quoting the article's conclusion:
"In Conclusion: Although a worm gear will always have a few 
complications compared to a standard gear set, it can easily be an 
effective and reliable piece of equipment. With a little *attention to 
setup and lubricant selection,* worm gears can provide reliable service 
as well as any other type of gear set." (bold is my change)

73

Roger (K8RI)

On 6/29/2015 5:10 PM, Richard (Rick) Karlquist wrote:
>
>
> On 6/29/2015 1:08 PM, Roger (K8RI) on TT wrote:
>> That's not correct!  It's the gear ratio! Not friction that makes the
>> worm gear winch self braking!  I can raise my LM470 tower to vertical
>> with one hand using my Dayton  worm gear winch.  With the double step
>> down spur gear winch I could barely raise it with two hands.  It was
>
> According to this reference:
>
> http://www.machinerylubrication.com/Read/1080/worm-gears
>
> "A second reason to use a worm gear is the inability to reverse the 
> direction of power. Because of the friction between the worm and the 
> wheel, it is virtually impossible for a wheel with force applied to it 
> to start the worm moving."
>
> The reference goes into a lot of detail about the many disadvantages
> of worm gears, which was my original point:  they have their place
> but are no panacea.
>
> My Fulton KW3000 has a 50:1 ratio.  It requires about the same effort
> going down as the previous Fulton KW2550 with only a 25:1 ratio. Going 
> up, the effort with the worm gear winch is double that of the spur
> gear winch.  And the effort scales with the load, just like friction. 
> We can argue whether it needs friction to work, but the fact of the 
> matter is that it has a boatload of friction.  I measured the handle 
> force with a torque wrench and it is over 60 foot pounds worst case.
> I really wanted the safety aspect of a worm gear winch, so I replaced
> the KW3000 with a motor driven 6000 pound winch with a 12 inch ring 
> gear.  IMHO, both of these winches are only good for about half
> their rated lift.
>
>> A good worm gear winch has more friction than a spur gear winch, but
>> turns "MUCH EASIER" than a spur gear winch for the same load. I have
>
> Again, that hasn't been my experience.  As always, YMMV.
>
> Rick N6RK
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk

-- 

73

Roger (K8RI)

---
This email has been checked for viruses by Avast antivirus software.
http://www.avast.com