chipper: heavier, 1000rpm flywheel better for smaller tractor? WC68, WM-8h, WC88

[orangetree]

Buying a PTO chipper. My rig is on the smaller end of viability with 21.7 pto hp. PTO lift is 1600lbs@2ft aft (also FEL + beet juice in all 4 wheels). My use case is primarily conifer (eg, soft), and mostly small (anything ~4" or larger becomes "firepit" firewood). The large input capacity seems great/necessary to reduce processing of larger branches, tree tops, etc - but I have no ambitions for 6" trees of any sort, and understand my tractor will require slow feeds on larger material anyway.

I am not understanding, *especially* for a ~underpowered use case: wouldn't the following not only chip well but actually be significantly more "kind" to my tractor:

• heavier flywheel: smooths out power demand (higher inertia), might transfer less impact to the PTO & 3-point
• 1000rpm vs 540rpm:
  • because it's belt driven (not direct drive) this should significantly ease wear on my pto drivetrain?
  • and it would have ~4x the inertia (rises with square of speed), even more effective than increasing mass

The common models recommended seem to be woodland mills WC68 and woodmaxx wm-8h. Then there is the WC88 which seems to combine the benefits of both (but is rated to require 50% more hp than the WM8h - ie more than my tractor has) I own implements from both companies, very satisified with quality of both. My pto is rated for both (on the lower end) wm8h/wc68.

• The WM-8h has both a heavier flywheel and belt-driven/1000rpm
  • it also has dual powered infeed and a lift-bar for the infeed rollers
  • but a clunkier design (much longer, and requires rear chute post). This matters for me, I am mostly thinning heavy pine/fir woods for fire (so i'm not driving on trails, but through the trees)
• BUT the WC68 folds (moves/stores smaller) and has easy flywheel access
  • it seems easy access to the flywheel will be very helpful (even ignoring blade access , cutting a lot of small stuff I understand I'll need to get in there to clean things out regularly?)
• enter the wc88 - which is NOT rated for my HP (35hp min) but would seem to combine some benefits of the WM8h (fast/belt slightly heavier flywheel) with the folding, accessible design of the WC68

Questions:

• am I thinking about the "wear on my tractor" correctly here?
• the WM-8h is rated for my tractor but the WC88 is not - they would seem to be nearly identical.
  • Is the WM-8h overly optimistic (understanding limits on larger stuff & feed rate obviously)? What are the downsides to the wc88 on my rig?
• practically speaking, even if the direct drive & mass of the WC68 is worse, would I notice any difference on mostly 4" softwoods with my rig?

Thanks!

 

[sea2summit]

The 1000 vs 540 is based on what you're tractor delivers for PTO RPM, nothing to do with the chipper per say. The flywheel of the chipper will probably have its own tac and recommended RPM probably close to 1200 rpm max.

The heavier flywheel will take some of the shockload off of the PTO and be more efficient overall, I would look there.

Having hydraulic feed with only 21 PTO HP is really going to take a lot of power, I'd look at a gravity feed chipper if I was using it on a tractor that size.

I have the Woodmaxx MX9900 and the difference between a 50 PTO tractor and a 60 PTO tractor is staggering, I was shocked it may double the speed. So moral of the story, PTO HP is still your friend when chipping.

 

[ericm979]

I have a Woodmaxx 8H which I run on a 37hp tractor with 32 hp at the pto. Chipping is one activitity where I wish I had a tractor with more power.

The flywheel intertia might help on a short branch that is too large for the tractor's power but with one more than a foot or so long the chipper will slow. When the chipper is slowed down because the engine can't keep it turning at full speed, the flywheel effect makes it take longer to speed back up.

Belt drive isn't going to make any difference. The belts don't slip and if they did they'd wear quickly. I don't see the chipper wearing the tractor unless you're trying to start the chipper with the tractor engine revved up, which will be hard on the clutch or PTO clutch.

The Woodmaxx WM8H and Woodland Mills WC88 are totally different designs with some common features like an 8" throat, belt drive, and being made in China but designed in North America. Woodmaxx's HP ratings are more optimistic, too much in my opinion.

There's video on youtube of a guy running a WM8H on a 21hp tractor. You can see (well, hear) how much it slows on what look to be fairly small branches.

 

[RalphVa]

If you have any hills you need to take the chipper up/down on, you need to also consider the weight. Our WC46 chipper is just over 500 #, and the weight is felt on the hill behind the house. In my mind the WC68 at 700 # would be too heavy for the B2601 Kubota or would have been on the 2025R JD.

I ran a MacKissic TPH-122 that take up to 3 1/2 inch stuff in the chipper chute for 16 years and a similar Troy Bilt Tomahawk for 10 years before that (a beast to maintain vs. the Mac a dream). The Mac did fine on the 18.5 engine hp JD 4010 (like a 2019E if they made them today). Think I stalled the engine once in 9 years operating it. The JD 2025R and Kubota B2601 just loaf along using the WC46 at 450 PTO rpm and 5 speed on the hydraulic feed (you'd really not want to use the 10 speed as it can really whip some tree parts around at you). Have had the WC46 for a couple of years. Have not rotated the chipper blades yet.

I take along a low lift hydraulic jack in the FEL to raise the input feed roller on the WC46 when it gets stuck. I've read that the Woodmax has something to raise its roller.

Chipping hp requirement only goes up by the square root of the wood diameter. So, your tractor could chip a fairly large diameter tree. Like I said, 18.5 hp is fine for 3 1/2 inches. Your 26 hp tractor could do up to about 7 inches. It would easily take the 8 inch machine at probably half input speed, but I doubt you'd want that much weight back there.

 

[ericm979]

Chipping hp requirement only goes up by the square root of the wood diameter. So, your tractor could chip a fairly large diameter tree. Like I said, 18.5 hp is fine for 3 1/2 inches. Your 26 hp tractor could do up to about 7 inches.

I think you are optimistic here. Chipping larger material takes a lot of power. My 37hp tractor can't chip 7" material, even when it's super easy to machine madrone.

 

[oldballs]

I can't address the physics of this technicality. I'd just say that 7 inches of any tree for a 21 HP PTO is too much. My Kubotas (B2620 & B2650) with 19 HP PTO work well with the WC68. But I don't feed anything larger than 3- 4 inches max thru it. As for hills and/ or woods for toting the thing around and operating.....My place is only moderaately hilly and there are no problems using or moving it around. I try to operate it on as level as possible seating....sometime using a plank to level it up behind the tractor. Setting the hydraulic infeed is important.

 

[orangetree]

I'd just say that 7 inches of any tree for a 21 HP PTO is too much. [...] 19 HP PTO work well with the WC68. But I don't feed anything larger than 3- 4 inches max thru it.

Yes, definitely. I envision the vast majority being 2-3" branch stalks with leaves/needles. No way I would expect my tractor to do well (or at all) on 6,7,8" wood, even if that's softwood.

 

[orangetree]

The 1000 vs 540 is based on what you're tractor delivers for PTO RPM, nothing to do with the chipper per say. The flywheel of the chipper will probably have its own tac and recommended RPM probably close to 1200 rpm max.

As I understand it, the WM-8h and similar have a 2~to~1 belt drive: tractor still operates at 540, pulleys ~double that.

Is this incorrect?

looks correct to me from the pictures: (see much larger lower pulley)

 

[orangetree]

Having hydraulic feed with only 21 PTO HP is really going to take a lot of power, I'd look at a gravity feed chipper if I was using it on a tractor that size.

Yes, it definitely takes power ...

I (anticipate) I'd rather be limited to (say) <= 4" fir or <=3" maple AND have feed, vs add an inch to those practical capacities but have to hand-feed *everything* - the vast majority of what I'd even want to shred fits in the smaller size range.

 

[sea2summit]

As I understand it, the WM-8h and similar have a 2~to~1 belt drive: tractor still operates at 540, pulleys ~double that.

Is this incorrect?

I would assume that is correct, really haven't researched it at all and didn't consider flywheel speed when I purchased.