My Bandmill Build Thread

[Brmorgan]

Well guys, I'm finally getting around to working on the bandmill project. I don't know how long it'll take me as my work schedule is really up and down, but I'm pouring as much spare time as possible into it right now. This week I got the main frame of the carriage built and squared up really nice. Spent way too much time welding in a T-shirt once - had a bit of sunburn the next day. Anyway here are a few pics:

Just laid the bandwheels out on the floor to take some measurements and get a feel for the size and scope of what I wanted in a mill. The wheels are 26.5" diameter. I want at least 24" clearance between the wheels at the narrowest point, and this would still allow me to cut a ~3' diameter log after squaring cuts are made. Anything larger I'll haul out the CSMs again to split it down. I don't have equipment to move logs that size at the moment anyway. If I build it for 24" center clearance, that would put me almost exactly in the right spot to use the 15'4" WoodMizer blades. Just trying to build it so the blades are a fairly standard size to make them easier to get, rather than have to have custom-made.

Got the frame put together. It's all 2" squaretube that I've salvaged over the years. It's square front to back and top to bottom, and accurate to within about 1/16". Believe me it took a lot of cutting, twisting, and re-welding to get it to sit nice and flat and plumb. It measures 48" between the side posts, 60" tall between the top and bottom rails, and 26" deep front to back total.

Here I've attached the secondary upright post that I will run the powerhead up and down on. It's 2" square Telespar, more commonly seen used as sign posts. It's available in many sizes in 1/4" increments, such that each size slides nice and snug over the next smallest size. I wanted to guide the powerhead on separate posts from the main frame posts, since they are much more difficult to keep square and aligned than two central posts. I had originally thought of going with a two-post design like the WoodMizer LT15, or better yet a single-post like the larger WoodMizers, but ultimately for my first build I decided to keep it simple and reliable, and possibly over-engineer rather than build too skimpy and have something that isn't nice and solid or expandable in the future.

This is how the post is attached to the carriage at the bottom - it's a 6" section of 1-3/4" Telespar welded to the frame, and the actual post slips over this and is held by (ultimately three) bolts. They hold it rock-solid.

A view of how the post is held at the top end. Basically the same idea, but since I want the post to be removable in case I need to remove the powerhead from the carriage, I couldn't weld this end on. So I welded a 12" section of the same 1-3/4" Telespar to a 4" X 12" X 5/16" piece of plate steel. I got everything lined up and plumbed perfectly, clamped it in place, and drilled out two 1/2" holes through the plate and the top rail. A couple more bolts hold the post to the top mount. That post is just as solid as the ones that are welded in place, so I'm not worried about strength at all. The mill powerhead will ride up and down on the 2" tube using a piece of 2-1/4" tube running overtop. There is a small piece on the post in this photo, but I have a longer ~18" piece that I will use, or at least as much of it as I can before running into top/bottom clearance issues. It slides very smoothly and I'm hoping it will work well. An added bonus of this stuff is that the holes are exactly 1" apart, so one could use them as positive stops for a depth adjustment, or just to put a stopper pin to prevent the mill from being dropped too low and wrecking a band on structure steel. Ultimately, I think I may install a second post staggered a half-inch from this one, and have a set of solenoid pins so I could have switch-controlled positive depth stops every 1/2". Or even a third post for 1/4" stops.

 

[Brmorgan]

Just a couple more pics -

To guide the mill at the far end, I am going to try using some rack-and-pinion gear track I had lying around. I tack-welded a length of 1-1/2" squaretube in and plumbed it relative to the other post, and tack-welded the geared track onto the inside. I had four sections, so I used the fourth to line up the toothing at the joints, since they were not all cut the same. The corresponding gear rolls up and down it nice and smooth. I will likely use a very stiff spring (truck valve spring or the like) to hold the guide gear assembly tight against the track - this should allow for any minor inconsistency in the parallel of the two end guide posts.

I guess I should point out that I will be building the powerhead such that it is also stabilized by at least the front two carriage frame posts, as I just feel it would be a more secure build that way. But the main cut accuracy and head lift will be determined by the center posts. As far as lift is concerned, I have two options - I could actually drive the gear in the track rather than just let it freewheel, or I could use a closed-loop chain hoist setup like the LT15 uses. Or, I could use a combination of the two, though getting the lift rate of the two different systems synchronized could be difficult. At this time, I'm leaning strongly towards the chain lift method since the chain also holds the brunt of the weight of the mill, and the closed-loop nature prevents a runaway fall of the carriage head while also pretty much negating the need for any kind of ratcheting mechanism etc. to hold the lift at a desired height.

I had this hand-crank winch kicking around and am looking at it as a possible option for a manual lift mechanism right now until I get a powered option figured out. I just had to take a picture of the "not for lifting humans" part though. Incidentally, the pitch of the big gear on this winch matches up with the pitch of the gear track, so I might try turning the gear directly with this just for kicks. I have a 0.9HP 12V starter/generator from an old snowmobile engine that could work, though it is very high RPM. Not sure how fast it would spin up under a heavy load like the weight of the mill - I don't want something too fast that it's hard to be accurate, and I don't want to have to play around with a bunch of big pulley reductions to make it work. I think just a small, cheapo electric winch would be best since it's slow and has built-in up/down, but I'd need one that I can remove the cable drum and install a sprocket or belt drive on. I have a 2000lb winch kicking around that I might pull apart a bit to see what I can do with that, but I'd rather get a smaller 1000 or 1500lb for the mill and keep the 2000 for the log arch project.

Anyway more pics likely to come early next week, probably won't have time over the weekend to work on it.

 

[mtngun]

Looks like a fun project.

Like the use of scrap metal. Pretty much the way I do things, though steel prices have fallen so this is actually a good time to buy metal for a bandmill project.

I hope to build a bandmill someday, though by the time I get around to building it, most of my home construction projects will already be complete and I will no longer "need" a mill. But "need" is beside the point.

 

[Coalsmoke]

Nice work on the mill. Nothing wrong with keeping everything manual and adding power options later on down the road.

 

[Metals406]

Looks like a good start!

 

[texx]

i like the rack and pinion idea a lot .
a rack each side and a rod ( shaft )going from one side the other so both sides are moved at the same time same amount .
filling that away for if i ever build a band mill.

 

[Brmorgan]

Yep that was the first idea i had, until I looked into prices... I salvaged the track and the single gear I have from the sawmill I worked at. I went to a local machine supply company, and just a single gear the same as the one I have - 16T, 7/8" ID bore - is $50 plus freight, and that was with a bit of a "store loyalty" discount. I didn't even ask about the track sections. If I were to do it though, I would run a chain horizontally across the top of the mill, with two 1" Acme rods vertically down each side, with a worm gear or some such right-angle drive conversion to drive the track gears.

I already had a bunch of #40 roller chain sitting around (about half of what I'd need), two matching drive gears w/ 1" ID bore, and two matching idler gears. So I decided to build a lift system much like that on an LT15 at each end of the mill so they both lift exactly the same, and the load is distributed equally across the entire frame. I'm building a 1" shaft across the top of the frame, direct-driven by a 4.4:1 hand winch with a slightly modified cable drum. Using the sprockets I have now, that would give me a little under 3" of lift per complete revolution of the winch crank. That's a tad on the fast side I think, but I'm going to see how it works out for now. I have lots of room to get smaller gears if I need to slow it down a bit. Ultimately I want to have it powered, but for the moment I just want it to work. I should have the lift system more or less finished tomorrow and will get some pics up once it's working.

 

[BobL]

Lookin and sounding good!

 

[Brmorgan]

More pics

Well it's at least starting to look like something. I was hoping to spend most of the day working on it today but ended up having to spend a bunch of time replacing the starter in my brother's diesel work truck. Geez parts are pricey for a Cummins. I did get quite a bit done though:

I got the chain lift system completely done at the main drive end, but still have to get the bottom idler sprocket welded in on the far end. The frame for the powerhead is done and being held level and square at the far end with a couple clamps for the moment. The chain lift is holding the weight of the frame at the near end, and doing a fine job of it.

I mounted the winch upside down, more or less to minimize the amount of #40 chain I needed. This also keeps the top of the mill frame wide open to mount other things like a water reservoir. The going rate up here for #40 is around $4/ft. I happened to have 7.5' kicking around that I'd scaveneged from old motorbikes but I needed close to 20', so it still cost me a few bucks.

A view from the other side of the winch. I cut the outboard side plate off the winch's cable drum and also cut the mounting ear of the side of the winch to accommodate the 1" pipe.This was slipped over the center spindle of the winch, and I drilled two 1/4" holes through the whole works, and bolted it together. This gave me direct drive from the winch to the shaft. However, since the second side mount of the winch was cut off, I had to position a bearing as close as possible to the side of the winch. I welded a piece of 1-1/2" squaretube coming down at 90°from the top frame and bolted the pillow block to that.

A backside view of the winch and chain sprocket. The sprocket is a 24 tooth, which I think is going to prove a bit larger than ideal. I'm going to try to get some 12T or at least 16T ones to step it down a little. I don't mind turning the crank a few more times if it gives me increased accuracy and takes less effort.

This is what I got set up for the gear track for the time being. I had an old arbor of some kind kicking around, 1"x8TPI thread on one end, then a collar, then more 1" diameter followed by some 7/8" and then 5/8" thread. Since the gear has a 7/8" bore and the only bearings I had around were 1", this worked perfectly for the time being. I will eventually get two 7/8" bearings and a piece of shaft and center the gear between the bearings. Although, it's seeming to me like the whole gear track thing is largely redundant with the second chain lift assembly at the far end. I may just cut it out and replace it with a second perforated squaretube post like on the other end.

 

[Brmorgan]

Here's a pic head-on with the bandwheels clamped on just to get a sense of how it might look. I put my 72" straightedge up on the bandwheel shafts for a reference. One of the wheels will probably end up going inside the frame uprights since I don't really need that much clearance between the wheels. Also, they will be hung below the horizontal frame to maximize vertical clearance between the band and rail.

 

[Coalsmoke]

Looking great. Post # 10 doesn't have a picture attached to it, just FYI.

 

[Brmorgan]

Heh, does now - that was about the last thing I did before going to bed last night, must have been a little too tired when I did it.

 

[Coalsmoke]

Yeah I here you on that. I think you'll have a mighty fine mill.

 

[Backwood]

Looking good opcorn:

 

[Brmorgan]

Went down to the scrap yard and picked up a bit more of that perforated squaretube stuff today. Got rid of the gear track etc. so both ends are pretty much symmetrical now. The lift mechanism is all put together at both ends as well. It lifts and lowers smooth as butter over the top 2/3 of the travel range, but is binding up and shuddering over the lower third. I'm not sure if this is an alignment issue yet but it shouldn't be too tough to rectify. The hand winch lifts the chain pretty much exactly 3" per revolution of the crank - if I go down to a 16T sprocket it should give me 2", and a 12T would give 1.5". I'm thinking I'd like to try the 16T - if it's lifting 2" per revolution, it would be easy to mark off 1/8 turn increments that would equate to 1/4" lift.

The platform is really nice and sturdy now. I must have raised and lowered it 50 times trying to figure out what was binding it up, and it is still sitting just as level and square as when I put it all together and had it clamped in place. I even sat on the platform while moving it to simulate the weight of the bandwheels (not the engine as well though, I'm only 170 lbs!) and it felt rock solid and still traveled up the guides nice and smooth. Well, the top part anyway.

It's coming together gradually. Much slower than I'd like, but I'd rather build it right the first time rather than have to rip it all apart later to fix an oversight. I'm sure that will still happen to some extent though - it's impossible to foresee everything. I have four 3" 90° V-groove wheels on order at a machine supply shop and they should be here next Tuesday, so once those are here I can start work on the base runners and guides. The guy who helped me had never heard of them before but told me he'd look into it for me. I got a call back within a couple hours saying he'd found some. They're about $12 CDN apiece, which I didn't think was too terribly expensive. I'm not entirely sure if they have a bearing in the center or not, all he said was that they're 3/4" ID bore. Either way I'll figure something out. I could always give them to my neighbor who made the band roller guides for me and get him to machine the center out to fit a bearing I guess.

 

[Coalsmoke]

Brad, you're right to not rush it, you will only regret it later.

About those wheels, I have some 3" but they are more like 1/2" ID bore and are cast iron / nodular iron (one of the two). There is no bearing in mine, but I drilled and tapped for grease zerks and stuck a grade 5 bolt through them and it works real well, very little rolling resistance with a high grade grease in there. However, my carriage is only ~ 400 lbs.

 

[Brmorgan]

The Vee wheels came in last week:

I think they'll work really well.. They're 3" diameter, and about 1-3/4" wide. They are 3/4" ID, with pre-greased needle bearings. I'd have rather seen ball bearings, but for $12.80 apiece I'm not going to complain. I end up paying way more than that for a good balanced 3" pulley.

I ended up ordering a few more sprockets and some chain, and changing the lift mechanism so that it lifts from the center of the carriage. However, I couldn't have a solid shaft from end to end across the center of the top, because there has to be clearance for the engine to protrude through the top when the band platform is raised. So I ended up putting the full-length shaft across the back of the carriage, and gearing that up to two small jackshafts which would carry the weight of the platform, one at each end of the carriage.

Rather than the big 24T sprockets I was using to lift before, I installed a 12-tooth #40 sprocket on each end of the main shaft. These are chained to the 24T sprockets on the jackshafts. A 16T sprocket is on the other end of each jackshaft, and these are what actually pull the head up and down. So, that gives me a further 3:1 gear reduction on the winch drive, which is already a 4.4:1 reduction from the crank. This setup lifts the head bang-on one inch per revolution of the crank, which will come in handy for quick adjusting. And without the weight of the bandwheels and engine on the platform, if I close my eyes I can't tell the difference between raising and lowering the lift as far as effort needed to turn the crank. My two year old cousin could do it. It wasn't overly difficult before, but I think this will work out a LOT better.

Inside view of the drive end. The chain ends are mounted to a 4" long piece of 1/4" X 1-1/2" strip steel. I was able to use solid 1" bar for the jackshafts, which will bear the weight MUCH better than the 1" pipe I have for the long main shaft. It was flexing pretty good under the weight with the previous setup. To secure the bearings, I drilled and tapped holes in the piece of 1/2" steel plate that they're on. It was a good workout tapping 1/2" X 13T NC threads by hand with the little 10" tap wrench that came in the set, and it actually did crack the tap holder so I have to take it back and get a warranty replacement.

View of the far end of the lift mechanism. Pretty much identical but in reverse & without the winch. The only work I have left to do on the lift is to clean up the welds on the 12T sprockets. They're so small there isn't much space to weld the hub on, and the bead is interfering with the chain riding over the tooth smoothly in a couple spots on both. I even used 3/32" rod at low amperage but it still put too thick of a bead down.


On a different note, I acquired another distraction from the scrapyard last week, something I've been wanting for a long time:

It's a 19.5 CFM Eagle 3-cylinder, two-stage compressor pump. It's in great condition, just a bit dirty, and has excellent compression. Just turning the flywheel over by hand gives a pretty decent blast of air out the exhaust. I paid $125 CDN which included the ~200' of good, contractor-grade 3/8" & 1/2" ID hose that's sitting next to it. It's the nice limp stuff with the coil springs at the ends to prevent kinking. I've been needing some more air hose as it was, and this stuff would have been worth more than what I paid for the works. This pump is rated for 3-7.5 hp, and I have a good 3-hp 240V motor that I bought new a couple years ago just for this purpose, though I never dreamed I'd end up with a head this big in my price range. I also already have a good 30-gal pressure tank which is a bit small but will work. All I really need is a pressure switch and some misc. fittings and I should have a decent compressor rigged up. The last thing I need is another project though. I need more time in the day!

 

[BobL]

Nice wheels and good looking compressor head too!

 

[Coalsmoke]

I'm enjoying the pictures. Your wheels have bearings ????????!!!!!! Mine were the same price, same color, same shape, book said they had bearings but both sets never had a bearing in them. Strange.

 

[Backwood]

My wheels look just like those too but I didnt get a good of a deal as you did. ( Hey Grainger... )
I run my angle at an L shape instead of looking like a rooftop like you show. It fit the grove in the wheel good , but now the wheels are not true round anymore, they have a flatspot or two. I need to redo my angle the rooftop way. It would give more surface area to bear the weight of the mill.