clogging chute on brush chipper...

[A_DAB_will_do]

Couldn't find a better topic to post this under, so I put it here.

My customer(tree-trimming business) has a chipper that is suffering from frequent clogging. I need someone with experience trouble shooting this type of equipment to offer suggestions. Recognize that the equipment in question is tired and has been repaired countless times in the past...

The chute on the chipper has had several repairs made to it; some by me and a few by someone with apparently poor welding skills.

Most recently, I was called to re-weld the chute, which had broken into 2 pieces.

Debris exits the chipper vertically, and immediately enters a rectangular tube that makes a 90° bend. From there the tube continues horizontally for about 5-6 feet. The chute had cracked all the way around at the junction from the elbow to the straight tube.

The tube had snapped off at the exit from the bend. A previous repair had been made using MIG/FCAW welding. At the repair, 2 flaps were located inside the chute, that lapped the weld joint on either side of the chute. These flaps may help funnel debris past the repaired joint; or they may be original equipment. I can't tell which.

Anybody seen these flaps in this type of equipment before? Or are they a hack that my customer's former welder put in place to make up for some shortcoming in his repair?

I'm not on the hook to fix this issue, I'm just trying to help out my customer.

I've suggested making a new chute, but this idea is a distant second choice for him. (He's frugal)

If it comes to makeing a new chute, anybody every custom fabricated one of these before?
I've debated the merits of making a new chute with round tube, instead of rectangular tube...It seems that the smallest projection inside the current chute causes debris to accumulate and eventually clog the whole chute up. I'm thinking that a round chute would be less likely to have this problem.

Thoughts, past experiences? Thanks.

[mla2ofus]

My thinking is the round tube would concentrate wear in a smaller area, therefore wearing thru sooner. I don't understand why the original design was for a totally enclosed chute unless it was for strength for the overhanging load. If you built a chute open on the bottom, wouldn't inertia keep the chips in the chute? If it was built w/ an open bottom, could you run a couple of braces from the point where the chute attaches to the chipper out to near the end of the chute to support the overhang? I've seen lots of these chippers in use but never paid attention to the chute design. Maybe the reason for the enclosed chute is to keep sawdust and leaf particles from drifting outside the the truck or trailer they're being blown into, tho w/ the velocity of them, I'd think plenty would wind up on the ground from being blown out of the truck/tlr.
Just my thoughts,
Mike

[Dualie]

The original chute was most likely a radius that had no sharp bends in it. I would venture to guess that the knives have been re sharpened so many times that the chips their making are to large to clear the chute adequately and just bind up in the choke point. i would say a new machine is in order but if you can beat a patch over it to make the 90 a larger radius i would do that.

[RWS WELDING]

i agree with dualie, also some more questions, is the engine running at full throttle? when the clutch is engaged does it feel positive? are the belts from the clutch to the chipping wheel adjusted correctly? on some of the newer models there is a dgital display of chippjng wheel r.p.m. is it to spec.?could possibly be engine is just so tired that when the wood leaves the feeder into the chipper wheel it lugs down too far not able to clear or launch the chps fast enough and end up getting caught in the chute.

[A_DAB_will_do]

Dualie, I must not have been too clear in my original posting. The bend in the chute is a curved radius, but the chute has a rectangular cross section. The radius in the bend is about 10", I'd guess.

My customer said something about re-sharpening the knives in the chipper, and checking some other things on the equipment....

According to my customer, the clogging problem has become more frequent since the last repair to the chute. Funny thing is that there's nothing either of us can see about the repair job that has affected the contour of the inside of the chute. We both agree on this fact...

I know his crew drops the chute when they take it off to clear a clog. I welded an angle iron frame around the exit of the chute several months ago, and it's all battered and bent now. I wonder if any of the slight dents or buckling in the chute could be accumulating to the point of creating this problem. This is why I was considering suggesting a complete replacement of the whole chute. I was also thinking that a round tube wouldn't have any corners for things to stick in. Seems as though the smallest accumulation of material eventually builds to the point that the chute is completely blocked.

My customer also had me lengthen the chute by about 18", about 6 months ago. I remember worrying that it would be easier to clog up if the chute were longer. I didn't hear any complaints after that modification, but I'm starting to wonder if this problem doesn't extend back to that change in design? Is this just an accumulation of old age and wear that his finally reached a critical point?

RWS, I haven't checked out the equipment while it's running. I don't know enough about this kind of equipment to make any judgements about how well it's running.

The chipper is a brush bandit, and while I don't know how old it is, I'd say it's been around for a long, long time...There aren't any digital gauges on this thing and it's got enough rust and bent metal on it that it looks like it's been through a war... It's got a diesel engine; but that's all I know at the moment.

I'll relay your questions to my customer as suggestions for where to look next for a solution to the problem.

Originally Posted by Dualie

The original chute was most likely a radius that had no sharp bends in it. I would venture to guess that the knives have been re sharpened so many times that the chips their making are to large to clear the chute adequately and just bind up in the choke point. i would say a new machine is in order but if you can beat a patch over it to make the 90 a larger radius i would do that.

[MarkBall2]

You said something about "flaps inside the chute" to help locate the bend. Depending on where the clog occurs, I would suspect that chips hit the flap & causes a disturbance that allows the build up of chips, which then causes a clog once enough chips have accumulated.

Is there a way to remove the guide flaps to the outside of the chute? That would make it smoother on the inside of the chute & possibly reduce the accumulation of chips.

When you lengthened the chute, is there still enough velocity with the chips to overcome that length? I would think a length increase should decrease the velocity, possibly allowing an accumulation of chips that lead to a clog. I'm also betting it's going to be a combination of things that is causing this.

[transit]

A photo of the chipper would be a nice place to start, I had a problem with my chipper and the flail/hammer screen bending. I welded reinforcements to the flail screen and all is well.

[Sandy]

My guess, and a guess only, is those flaps may be there to direct and concentrate the exiting flow of chips while not using an extension. There is usually some form of constriction at the exit point so the chips don't come out of there like confetti out of a shot gun. A choke so to speak. As chutes do tend to cause clogging issues it can be desirable to operate without the bolt on extension when doing clear and spread operations. If chip removal is necessary then 99% of the time the extension is required so then those flaps become un-needed and possibly problematic. Especially if the client has extended the tube beyond the original design of the manufacturer.


How about running around till you bump into some local "Davey Tree" type of guys, the ones that do trimming for the pocal power co.? If anybody can tell you the ins & outs of chippers, those guys can. They have to live with them 8 hours a day, good design or bad. If nothing else they can tell you what they would like to see in chute design.

[the hat]

As was mentioned earlier the chips may be too large to flow smoothly.The blades HAVE to be sharpened by someone is has the proper equiptment and knowledge to do them right.There are 4 blades mounted in pairs 180 Degrees apart and in the bottom of the drum housing is an anvil that must have a clean,wll formed 90 deg edge that is adjusted
as close as possible to the blades without hitting them.The service manual has a templete
for the anvil.If the blades are not sharpened all the same you can't get a good adjustment on the knives=large chips.Also I have never seen any flaps on the inside,it should be smooth with nice transitions. HTH Bill

[A_DAB_will_do]

Transit, I'll snap some photos the next chance I get....

Mark, Sandy, the hat:

Thanks for the confirmation about the flaps. I suspected that my customer's former welder may have added the flaps to cover up some rough spots created by shoddy welding technique. Or maybe they were there when there was no chute extension, to "choke" the stream of chips and keep them from going everywhere. So far as I know, my customer always uses the extension to funnel chips into a truck for disposal.

The chute swings from side to side, and I think it used to be adjustable up and down. that adjustment is gone now. Thanks for confirming my suspicions that there may be several contributing factors to the overall problem.

As to sharpening technique; I'll pass your comments along to my customer, and let him take it from there. I don't know what his level of expertise is when it comes to maintaing this equipment...Right now, I'm just caring for sheet metal, boxes, hinges, and other miscellaneous structural repair work. He has someone else that does engine maintenance, and I think he handles the detailed equipment maintennance, like sharpening blades and adjusting the machine, himself.

If adjustments and maintenance of the blades/anvil doesn't solve this problem, I'll cut out the repair I just made and remove the flaps. Then I'll smooth any defects out of the inside, and re-attache the chute. Given what I've seen while making other repairs, I may also end up rebuilding/reinforcing the elbow in the chute too. I've already patched a hole in the outside radius where years of chips wore a hole in the steel...I should say I removed a shoddily made patch that had failed. There are lots of thin spots in teh whole chute; which is another reason to consider rebuilding the whole thing from scratch.

If we go down that road, any more opinions on whether or not a round chute made from pipe would serve better than a chute with a rectangular cross section?

[transit]

Just remembered another thing I had to fix. A good deal of the chip ejection depends on how much air is blown to carry the chips along, any chance the blower is worn?

[MoonRise]

Pretty much what has been said:

- chip size (blade sharpening);
- chute length and 'condition' (dents in the chute could have altered the 'flow' just enough that in combination with a bunch of other worn-out conditions that the flow isn't flowing);
- sufficient air flow the chips through the duct (worn blower perhaps);

Rectangular duct shape shouldn't really matter. Usually the duct is waaaay bigger than any chips!

Primo for the duct radius would be some hard plate smoothly bent or some smooth 'mild' hardface. Cause as you've seen and know, that's where the chips are slamming into and rubbing most on the inside of the duct.

[lars66]

Has anybody set the anvil clearance after the knives were sharpened??? Another suspect would be anything inside the chute after being worked on, suprising how little can cause them to plug.