Winch calculations

[tree grower]

I am fabbing a M6 Braden winch into a psuedo-Farmi for firewood skidding. If I Google Braden winch, there is an excellent 40-page manual. On page 39 is a table which includes max input RPMs and line speed in Ft per minute for many Braden models, but not the M6. I emailed Pasccar, the current manufacturer of Braden, and they sent me an old M6 brochure with some specs, but not all. Soooo, we resort to extrapolation.

With a worm gear reduction of 34:1, I assume 34 revs of the worm = one rev of the gear = one rev of the winch drum. With a 5" winch drum diameter, one rev = 16". At 300 RPM input speed, that is 4800" or 400 ft per minute. I think 100-200 ft/ min is plenty fast enough for a log to be travelling behind a winch, so I would need to cut my input speed in half--easy to do with a jack shaft and a small sprocket. (PTO speed 300 rpm to jack shaft, 12 tooth sprocket #60 chain to 24 tooth sprocket on worm)

Request critique of my assumptions and calculations. Thanks in advance.

 

[rogerius]

I am fabbing a M6 Braden winch into a psuedo-Farmi for firewood skidding. If I Google Braden winch, there is an excellent 40-page manual. On page 39 is a table which includes max input RPMs and line speed in Ft per minute for many Braden models, but not the M6. I emailed Pasccar, the current manufacturer of Braden, and they sent me an old M6 brochure with some specs, but not all. Soooo, we resort to extrapolation.

With a worm gear reduction of 34:1, I assume 34 revs of the worm = one rev of the gear = one rev of the winch drum. With a 5" winch drum diameter, one rev = 16". At 300 RPM input speed, that is 4800" or 400 ft per minute. I think 100-200 ft/ min is plenty fast enough for a log to be travelling behind a winch, so I would need to cut my input speed in half--easy to do with a jack shaft and a small sprocket. (PTO speed 300 rpm to jack shaft, 12 tooth sprocket #60 chain to 24 tooth sprocket on worm)

Request critique of my assumptions and calculations. Thanks in advance.

Not sure if I understood corectly but here is my interpretation:

- the PTO(@300RPM) engages with a worm gear from the winch (reduction 34:1) and will result in an outlet of 8.82RPM conected to the winch drum. Based on this, you will have a speed of 16"*8.82 = 141"/min or 11.76ft/min for 300RPM. But I assume you can adjust the RPM if you need more speed.
- how I said, not sure if I understood correctly, so don't blame me.

 

[tree grower]

Well-that's what I needed-another set of eyes. You are correct-300 PTO rpms = 8.8 rpm of the winch drum x 16" = 12 ft per minute. Pretty slow. If we assume a desired line speed of 150 ft/ min, that is 1800" / 16" = 112 rpm of the winch drum. At a 34:1 reduction, my input needs to be 3800 rpm. To achieve 3800 I need to multiply maximum 540 rpm x 7, or comfortable work speed of 300 x 12. Seems like an awful increase--too many moving parts moving too fast.

I think the first question to be answered is " does a 34:1 reduction rate actually mean 34 turns of the worm to one rev of the drum?" I suppose I could start turning the input sprocket with heavy gloves on, and count revolutions.

 

[David Devuono]

Its one thing to be in the cab of a tree farmer hauling in some logs at 150ft per min into a log cradle. Its another thing to be standing beside a braden winch with your hand on a lever, standing anywhere near the cable. My experience with a high speed winch is the Warn 8274 at close to 75 ft\min (no load) and it was fast but at least you had a 10ft remote. So at 540 rpm PTO you could get 20 ft\min on the 5 inch drum. Realistically though you may have 3 wraps of cable left on the drum for shorter pulls so effectively you have an 8 inch drum now with 1/2 inch cable and your 540 rpm line speed may be 30ft\min. Just guessing, 11 inch wide drum with 4 cable layers, 3 layers give 30ft\min with 22x(8x3.14) \12. I am trying to say that you might be able to realize 30ft\min on the first 45 ft of cable played out. I spent many hours hauling logs for my last project without a winch. Get in as close as I could, hook up chain to log, back up till tractor spins tires, use loader to inch log forward, drop loader and back up again until stuck, etc etc.

 

[Chilly807]

To get a realistic look at what the factory winches are capable of, I'd suggest looking at a parts list for a logging winch. It might have the gear ratios or gear sizes. As far as I can see, all a factory built winch has is a small input sprocket driven directly from the PTO, and a chain driving the large drum sprocket.
I have no idea what the actual ratio is, but I'd say 70-100 fpm recovery speed is about right under ideal conditions. If you can achieve that at 540 rpm, then you're golden, since slower is often better in many cases.

From the Wallenstein parts lists, it looks like the main drum sprocket is 60 teeth, and the drive sprocket is 10 teeth, so that would give you 6:1 reduction. 540 PTO = 90 drum. That's an FX 65 winch.

Sean

 

[easygo]

I'm in the process of building a similar winch that will have a former tow-truck winch as the power. It has 40:1 gear reduction and I calculated that if I use a 20 tooth drive sprocket and a 10 driven socket that will give me about 35ft/min on the bare drum and about 65 ft/min on a nearly full drum recovery speed depending if I run the PTO at 540 rpm. However. I do not intend to run the PTO at full speed but more like in the max torque range that is about 1600-1700 engine rpm. I don't know exactly what PTO speed that will give me but I would guess around 300 rpm.

 

[Gordon Gould]

Sean is pretty close. On my Farmi the input sprocket is 14 teeth The drum has 66 teeth. The drum diameter when full is 8". If I run at 1600 RPM or 320 RPM on the PTO it is plenty fast enough for me which looks like 140 ft/ min if I did it right.

 

[plumbstraight]

Be aware that you will have to operate the winch from the tractors seat. As there is no way to stop it unless you declutch your pto.

I can also tell you that with that gear reduction, a 20 hp tractor will part a 3/8 cable with ease if you have any sort of blade to hold the tractor in place.

The other problem with this winch is that it will not unwind without it in freespool. If you pull up tight it will not release your load without slack in the line.

I have built many winches for 3pt hitches. Good luck with yours.

One thing to consider if you have a good hyd sys. Run it with a hyd motor, that way you can back it off if need be. The other thing is it might give a bit more speed, less pull, but if it will pull the tractor backward with the brakes on that is enough.

 

[tree grower]

Thanks for all the input. The free spool issue is one I will have to work with to get a proper feel. I have considered hydraulic drive, but i have no experience with hydraulic motors. The winch will be used on a Ford 850 or Ford 1700. Both have 1800 psi operating pressures, and I can't find the flow specs. The auxilliaries on the 1700 operate a FEL, and to add another hydraulic attachment would probably result in poor performance of all. Regarding engine / PTO / winch speed I think engine speed of 1200-1600 is my goal, with PTO speed of 300 for calculations. Keep it coming--I would rather get my knowledge from reading this computer than suffering accidents in the woods.

 

[Chilly807]

Plumb's got a good point about the ability to disengage the winch quickly. If something binds up solid, and the odds are it will, you have to go to the tractor to kick the PTO out of gear, which is the last place you should be if something breaks. You may find the PTO won't disengage easily if it's under a lot of strain as well.
The other option is to sit on the tractor with a foot ready for the clutch, and again if something breaks, that's where the cable's going to go.

I think it's worth researching the hydraulic drive options, or shop for a good used forestry winch. The pull cord that comes with them is 20 feet long for a good reason.

I've thought about piecing together a winch myself, but stopped at the clutch stage. If I were building one, it'd be hydraulic.

Sean