[TowerTalk] Worm gear winch

Fri Apr 4 16:29:39 EDT 2014

On 4/4/2014 3:00 PM, Mike Reublin NF4L wrote:
> I bought a Fulton KW3000, and I think it's a true worm gear drive. It has a 51:1 ratio. I plan to use it to raise my fold over tower. I'm powering it with a wheelchair motor.

It is a well constructed winch, but look at the large gear.  It's a 
shallow spur gear, not a worm gear wheel.

Technically it is a worm gear drive but all worm gear drives I've seen 
the teeth were cut at an angle to match the worm for the best strength, 
durability and smooth operation.

In addition many, but not all worm gear wheels are cut to match  the 
radius of the worm, so it sets down into the wheel. Using a spur gear 
reduces the contact between the two gears to a small point that has to 
bear all the load This can increase wear and friction compared to a 
larger, smooth, well lubricated surface.

The first photo on http://www.rogerhalstead.com/Gears.htm shows a worm 
gear wheel (Ignore the dirt). Note the angle at which the teeth are 
cut.  This one also has the radius cut to match the worm.  A large 
portion of the face on each tooth bears the load/contact area.

73

Roger (K8RI)

>
> In one of the views here http://www.etrailer.com/Winches/Fulton/FKW30000103.html you can see the gears.
>
> 73, Mike NF4L
>
> On Apr 4, 2014, at 2:13 PM, Roger (K8RI) on TT <K8RI-on-TowerTalk at tm.net> wrote:
>
>> On 4/4/2014 12:26 PM, ftravanty wrote:
>>> The only type of hand winch I would trust is one like a Fulton 1500 or 2500 that has a self actuating brake, and is in good working condition. A winch with a re moveable handle which is part of the self actuating brake, or one that can free wheel, being held by muscle power, can be very dangerous for tower work.
>> I like the latch on mine and other than a lapse in judgement feel it's quite safe.  Going up or down, the latch only lets you go in one direction and if you let go, it can't freewheel.  Noisy, but adds little friction to the work.
>>
>> I'd like to get a worm gear drive and convert it to a real worm gear, worm gear wheel type drive. They take very little effort on the crank, but the gear ratio is such that it can't freewheel when the driving force is applied from the output end. I think it'd be worth the extra money.
>>
>> A single flute worm with a 20 tooth worm gear wheel would have a 20:1 ratio, while a 2 flute worm would have a 10:1 ratio with the same size worm gear wheel. The conversion is fairly simple as you only need a worm gear wheel of the right diameter and pitch which should be the same # of teeth you have in the original setup.  They do need a fairly rigid mount.  (no play in the gears and they should be fully meshed).
>>
>> If you really want to know if it will be self locking it  "depends on the lead angle, the pressure angle, and the coefficient of friction; however, it is approximately correct to say that a worm and gear will be self-locking if the tangent of the lead angle is less than the coefficient of friction." (Wikipedia) <:-))
>>
>> 73
>>
>> Roger (K8RI)
>>
>>
>>
>>> Frank W9JCC
>>>
>>> On 4/4/2014 11:00 AM, towertalk-request at contesting.com wrote:
>> When using digest replies, please include the subject other than digest number.
>>
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