I thought I would go ahead and start a new thread for this instead of hogging the other screw chunker thread. I am debating on what bearings to use on the 2” screw shaft. I can turn the ends down to 1 1/4” and use two pillow block bearings I have, or I can use these.
These are the bearings from the old machine that I robbed the 2” shaft from. They have grease zerks that go to a grooved 1/4” thick bronze bushing. They also have a 1/4” thick bronze thrust bushing. What do you guys think?
My 2 cents worth says that pillow blocks (at least on the feed side) would be less obstructive (in the way). The thrust bearing on the back side might be necessary.
Thanks Don. That big bearing is actually smaller than the flights, so I don’t think it will be in the way, we’ll see. I just don’t know how they would hold up. It will only be going 125 rpm and I will probably only be using it 2-3 hours per week.
I chucked up the flights in the lathe and got them true with a little bit of bevel to cut down on the grinding.
Don’t underestimate the power requirement and forces involved. I posted a lot about the screw chipper I made roughly decade ago. I turned the screw from solid bar. I drove it with a tractor. My tractor has a weak engine. It was rated for 32hp on a 540 rpm pto. It didn’t work. I added a transmission with 4:1 reduction. It still was only able to chip 1" square hardwood. I’d like trying a larger tractor just to see if more power could make it run even partially like I had envisioned.
Ron, thanks for the reply. How are you doing? It was nice talking with you at argos last year. I found the pictures of your auger you made. That is one beautiful piece of machining. I am wondering if the reason it was taking so much power was the diameter of the shaft between the flights. It looks like the wood had nowhere to go and would jam against the shaft? This is only speculation as I have zero experience with this. Anyway, it is fun to experiment with this stuff since I have the time now that I am retired. After bending my flights and trying to line them up on my shaft, I can see why you chose to machine yours. I don’t know if it was because of the old steel robbed from an old boiler having different hardness in different areas, or me not putting the flights in the bender EXACTLY the same for each one, but my flights were not all bent the same. Still trying to figure out what is going on.
Hi Ron,
I used to design pressure vessels, including a few boilers. The steel we used was 516-70. It is corrosion resistant, has good weld characteristics, and is tough. Toughness is measured by Charpy impact test. If you manage to complete your project I suspect you’re great, great grand kids will still be useing it.
Rindert
Maybe I don’t understand the situation. The beveled edge makes me think you will want to weld them in the orientation in the first picture. Anyway, I would took for a way to weld them before final stretching.
Rindert, thanks for the reply. I had seen that video and doing it that way had crossed my mind. The problem is the edges need to be the same distance apart all the way from one end to the other and then they will all have the same pitch. When I tried to make that happen with my flights the spacing and pitch angle varied a lot.
Johan, I really like that idea, but then I looked at the branch being fed in. If we had different spacing on the flights, we would be trying to feed the branch in at different rates, which would cause binding (I think). I am no expert here on this, but I am stubborn enough to keep trying till I get it figured out.
You could be right, I as well as Wayne have no experience with screw chunkers, having the same spacing until it’s cut off which you know exactly where it would be and then directly step up the spacing a notch, and have the screw feed out the cutoffs a little faster. A two different spacings screw if you will, probably easier to make instead of all the wings being different.
I’m just afraid chunks will get stuck in the flights instead of being transported out
Edit: I think the second spacing should be bigger than the diagonal measurement of the thickest chunks you are going to feed in.
I’ve only seen in action and the resulting chips made from conical screw chippers:
This a video put up by a members for-sale Laimet HP21 in the DOW for-sale section.
Other Laimet sponsored videos can be searched up to show that the conical screw types actually from the decreasing diameter surface down cut, then peal-off layers of wood chips progressively. Then those being sucked up a to be blown transferred out, by a separate blower section.
Non-tapered flight section would seem to being have to work-bite across the whole log inserted at one time. Actually completely different. I can’t help but think this will need multiples greater power and torque to operate.
Steve unruh
Note: I did edit out my suggestion for stationary fingers to clear between the flutes. GarryC.
pointed out that that would not work with the moving spiral motion. S.U.
If I was going to increase the space between the flights, it would be the thickness of the flight. Most of the handmade screw chippers, I don’t think are perfectly spaced.
As far as building the flights, probably the easiest is to get them spread like you have, then weld them together, slide them onto the axle, attach one end, then beat with a hammer into position. You can also attach a come along or winch at one end to help pull the whole thing and tack weld them when they get in position one at a time until you get to the end.
And here is one showing the dramatic diffnerces created by Inputs-In vesus Results out.
Watch the chipped “dusts” flying at behind the working man when not pre-cleaned of all whiskers beforehand. Versus the bouncing large fuel grade chips made from a bare log section:
Hope the “Can Woodchips Be Woodgassed?” guy see’s this. Once all mixed from a just-reduce-it-all-down operation then the sorting/classifying separation must be done.
Better off at chipping instead of blowing all mixed up; dropping into a sloped rotating screened separator like PeteS. shows. Or onto a grid mesh conveyor for separation.
S.U.
Steve, where do you see these? I can’t see how you could have anything stationary between the flights without the flights shearing them off as the shaft turned.
You are correct Garry. Apologies.
I am mis-remembering from over a decade ago, now.
Sigh. Mis-remembering again. Getting old ain’t for the feint of heart.
S.U.
