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Building a simple PTO Drive for a ZENA® mobile welding system or a PTO driven DC battery charging/battery boosting system.

Our standard model PTO drive welding system is a rather exotic and, therefore, somewhat expensive product.

It comes in only two models -- a 200 amp system and a 400 amp system.

It is built to specifications defined by military and commercial underground mining customers. These specifications define a self contained unit built almost entirely from corrosion resistant air craft aluminum in which all pieces are CNC machined for assembly by means of threaded stainless steel fasteners.

The result is that the enclosure and drive system cost much more than any model of welder that will be installed into the enclosure. Perfect for customers who need a product that can easily be air freighted anywhere in the world and for which perfectly fitting parts can be obtained easily -- and installed by an individual armed only with basic hand tools.

However, building a do-it-yourself PTO drive welding (or DC power generating) system is fairly easy -- using scraps of steel and other parts that can be obtained from Agricultural Supply Retailers. And, rather than being limited to to sizes, you can build a unit that can drive a 150 amp, a 200 amp, a 240 amp, or a 250 amp ZENA welding power generator -- or a dual generator 300, 400, 500 amp, or larger PTO drive welder.

To this end, we offer the following information which contains general instructions on how to proceed with the project as well as some suggested sources of key parts that can make the process of building your PTO drive welder simple.

For do-it-yourself (and even factory built) PTO drive systems we recommend building a simple transmission made up of a frame assembly mounted to a 3 point tractor hitch platfform -- cradling two shafts mounted to the frame assembly with raised pillow blocks -- one with a PTO spline on one end and the other a plain shaft. Both shafts are also fitted with stop collars to prevent front to back motion.

The two shafts are mounted on elevated pillow blocks -- with the splined shat fitted with a single large diameter double 1/2" V or serpentine pulley (a serpentine pulley drive, although a bit more complicated and expensive, is recommended for OEM applications). The pillow blocks that support the plain shaft are mounted so that they can be moved outard from the plain shaft to tighten the 1/2" drive belts.

The plain shaft mounts parallel to the splined shaft and holds two 1/2" double V pulleys, one large (two large ones for a dual generator system) and one small -- with the small one being driven by the large pulley on the splined shaft. The large pulley (or pulleys) on the plain shaft drives one (or two) ZENA® welding power generator(s).

Optionally, one can use a spring-loaded belt tensioning system to insure proper belt tension -- and to avoid the necessity of moving pillow block/pulley shaft position.

Spring-loaded tensioners will work for both serpentine and for V belts (though the type of pulley fitted to the tensioner will differ).

Note that if spring loaded belt tensioning is NOT used in the design (required for serpentine belt drive -- optional for V Belt drive) some mechanical means should be included in the design to allow the position of the two shafts to be adjusted for belt tensioning,

By adjusting pulley diameters -- we can easily have the welding power generator turning at our target speed for welding (between 6500 and 7500 rpm) with the tractor engine running at a speed at or near its 540 rpm PTO speed.

For example, below we show suggested pulley sizes for a drive system that will allow the generator to reach welding speed when he tractor PTO shaft is rotating at about 500 rpm. When this same pulley set is used on a tractor with a high speed (1,080 rpm PTO), and a reasonable amount of available power at lower engine speeds, the engine speed necessary to drive the unit can be much lower.

Other ratios are possible -- giving the ability to have the welding power generator tuning at its operating speed at virtually any tractor engine speed desired.

The specific V pulleys that we would use for the example above when driving a 200 amp generator factory fitted with our standard dual 2.8" V pulley would be:

  • two (or three for a dual generator system) double bushing bore 1/2" V pulleys 11.35" OD (pitch diameter 10.6" when used with 1/2" bottom cog automotive V belts)

  • one double bushing bore 1/2" V pulley 3.75" OD (pitch diameter 3" when used with 1/2" V belts)

These pulleys yield a drive ratio of approximately 13.37:1 -- driving the generator to 7000 rpm when the tractor engine is running fast enough to produce a 523 rpm PTO speed.

Most of the parts needed for a unit as described above -- other than a quantity of 5/16 and/or 3/8" angle for building brackets and pillow block mounts onto a PTO frame equipped carryall -- are available from Agri-Supply and McMaster Carr.

See the following list:

Major Components --

Do-It-Yourself PTO Drive Assembly for ZENA® Welding System

Item Name/Num Description Est. Unit Cost Qty Total
AS 65060 3 Pt Hitch carryall Fork Attachment 109.95 1 109.93
AS 18151 1-3/8" X 6" X 12" Shaft with Spline End 47.49 1 47.49
AS 17955 1-3/8 " Cast Iron Pillow Block Bearing 14.49 2 28.98
AS 14562 1-3/8" SHAFT SET COLLAR 2.99 4 11.96
Mc 1497K601 Keyed Steel Drive Shaft, 1-3/8" OD, 5/16" 51.14 1 51.14
Mc 6361K42 Iron Pillow Block w/HS Steel Ball Bearings 7.066 2 141.32
Mc 6209K135 11.35" OD SK Bushing-Bore 1/2" V-Pulley 58.45 2 116.90
Mc 6086K522 1-3/8" Bore, SK Bushing 30.35 2 60.70
Mc 6209K111 3.75" OD SH Bushing-Bore Dual V-Pulley 26.40 1 26.40
Mc 6086K32 1-3/8" Bore SH Bushing 16.73 1 16.73

Suppliers for the parts noted above are indicated by part # prefix:

AS = Agri-Supply (800) 345-0169

Mc = McMaster-Carr (404) 346-7000

ZENA is a trademark owned by ZENA, Inc. for its welding systems and related products.

Protected by US Patent 6,512,199. Other US & Foreign Patents Pending

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