BobL's next CS mill

[Timberframed]

BobL, Being a concrete/stone cutting chainsaw, the pipe is the water inlet that goes into what would be the oil tank. Again I like the advantage of being able to cut either wood or stone. I agree to your disagreement it's just that I'm happy as a pig in mud right now with it. Believe me there will be some modifications and improvements as time goes by.

 

[BobL]

BobL, Being a concrete/stone cutting chainsaw, the pipe is the water inlet that goes into what would be the oil tank. Again I like the advantage of being able to cut either wood or stone.

I see - thanks.

I agree to your disagreement it's just that I'm happy as a pig in mud right now with it.

Good on you!

Believe me there will be some modifications and improvements as time goes by.

OK - no worries.

 

[BobL]

Will it work

I did a bit more work on the new mill this week - mainly on the height adjustment cranks and the bar nose holding mechanism.

Here's where it's currently at.

Yes it is bloody heavy so it should self feed very nicely.
I will be moving it around over distance with a set up pump up wheels I found by the side of the road.
I'm setting it up initially for my 44" bar I got cheaply in 2008.

The mill rails and height adjustment is basically complete.
There are three all thread rods that drive the height adjustment.
2 of the all threads are inside the C-section verticals on the inboard side and there's one crank and a chain linked to the other side driven by this crank.

The cogs are from an electric bike kit and have solid little 5/32 keyways for a very positive drive. I'm still hunting down some old school bike chain because racing bike chain is too narrow.

The outboard height adjustment all thread is exposed and centrally located and driven by this crank.

The knurled ally knobs are left overs from another project. I like using the metal work lathe and whenever I get on it I usually make a couple of extras of everything just in case I mangle something later in the project.

 

[BobL]

Now - Big question - will this work?

So far there's nothing really different with the design of this mill so I thought I'd throw in something different and just play with it and see if I can get it to work.

Here's a shot of the nose.

Here's a close up of the top part of the nose.

Here's the view from the end of the mill

And here's the underneath.

As you can see I'm using a hard nose bar bolted (B2) to a small angle iron A-frame on the nose end of the mill frame.

The sprocket (SP) is a replacement sprocket for an oregon bar (cost $13) that has a long T-Nut (T) bolted to the underneath of the sprocket that can slide in a 1/2" wide slot (S) in a piece of 3/16" steel welded to the A frame, allowing the sprocket to slide towards or away from the bar nose

The springs on either side of the sprocket are located on a pair of long bolts (B) that run right through to the end of the mill. The bolts pass through allowing the springs to apply pressure to a bolt (B3) running through the nose of the sprocket. This should keep the chain moderately tensions at all times even when it expand due to heat.

The idea is, I will set the chain tension nominally at the inboard (Saw) end and then apply further spring pressure to the chain at the nose.
I'm hoping this will ;
a) enable me to adjust the chain tension without always unbolting the bar bolts on the saw, ie even during a cut so if the chain gets loose I do not need to pull the mill from the log and tension from the saw end (I'm fairly confident this will work)
b) take up some of the chain slack when the chain gets hot.

The springs I show are just sme exemplars that my buddy Frank gave me and are unlikely to be the ones I end up using as they are too weak. I might try some big motor cycle engine valve springs or similar.

I have no idea if the springs to take up the slack idea will work. If it doesn't I will toss the springs and just shorten the T bolt and use the T and B bolts to lock the sprocket. I should still be able to make small adjustments to the chain tension on the outboard end using the B bolts.

Some other things to do on the nose end are;
1) Add some ally plate to cover the A-frame so when the chain comes off the cutters bite ally and not steel.
2) replace the outer adjustment nuts for the B bolts with something that might even be hand operable ie no spanner required.
3) Add an Aux oiler
4) Add a cover to the exposed drivers between the bar and sproket, if something falls in the the chain might jump the bar
5) Flare the groove on the incoming chain side on the sprocket
6) Add some ally collars to B3 so when the chain comes off the drivers hit ally and not steel

So what do you reckon, will it work?
I'm surprised no one has tried it before, well I haven't heard about it being tried.

BTW it might look incredibly complicated but loosening both B bolts and removing the top B bolt will enable the chain to be removed from the saw without removing it from the mill.

 

[DRB]

I think that the springs will have to be fairly stiff. When the cutters are cutting they will apply a lot of pull on the bar tip. The springs may start bouncing as the chain cutters load up and unload through the cut?

It will be interesting to see how it works out. What ever you do be safe.

 

[BobL]

I think that the springs will have to be fairly stiff.

I agree they will need to be stiff.

When the cutters are cutting they will apply a lot of pull on the bar tip. The springs may start bouncing as the chain cutters load up and unload through the cut?

I agree, hopefully they don't load and unload constantly all at the same time.
To reduce (harmonic) bounce there's also the possibility of, like a car valve, of placing a smaller spring inside a bigger spring.

It will be interesting to see how it works out. What ever you do be safe.

 

[kirkeg]

those bar tips look great! Betterbuilt and I were just talking about an idea like that w/ a replacement tip. nice to see someone put it together.

you have some goood ideas there. Can't wait to hear how they work!

"When the cutters are cutting they will apply a lot of pull on the bar tip. The springs may start bouncing as the chain cutters load up and unload through the cut?
I agree, hopefully they don't load and unload constantly all at the same time.
To reduce (harmonic) bounce there's also the possibility of, like a car valve, of placing a smaller spring inside a bigger spring."

harmonic resonance can tear things apart!
and of course there is the famous Tacoma Narrows Bridge collapse!

BB's saw powerhead started bouncing a bit when self feeding but was quickly remedied w/ a bungee cord.

Not a big deal in this application but something to be aware of... besides i find interesting to say the least.

 

[betterbuilt]

I really like where your going with your mill. Do you remember this picture?

I'd like to build something like that, but I wasn't sure how to build the tensioner mechanism. I'm watching your progress. nice work.


huebi posted that pic and this video.
http://www.youtube.com/watch?v=32_kTPHUfA4


here's is the thread with the pictures
http://www.arboristsite.com/showthread.php?t=127243&highlight=chain+tensioner

 

[BobL]

I really like where your going with your mill. Do you remember this picture?

I certainly do remember that picture and that whole thread. It's one of the threads that got me thinking about chain adjustment at the outboard end of the mill. The last sentence in that thread is me saying "Double ender sounds like the way to go though. I might just make my own ?" I would have made this mill earlier if I had not been away between April and August of this year, and come back with mangled fingers!!

Regarding harmonic resonance tearing things apart, I'm familiar with this as I teach this stuff at work. It's usually not that hard to deal with provided one can see the onset occurring and some adjustment or variability is designed into the system. In this case it should be a matter of just changing the springs or arrangement of springs, like putting another smaller spring inside a bigger spring

With long bars I run the chain quite tight but I always worry about it being too tight and about the high strain regular chain adjustment places on the relatively small chain tensioner. With this new setup, and whether I do or do not use the springs, I should now be able to set the chain tension accurately and reproducibly using a cordless driver ie set the clutch at the required setting and run the driver until the set clutch engages.

It's gonna still be a while before I can try it out because I still have to make the inboard end of the mill and the amount of time I have to put towards it is going to be small.

 

[demographic]

I certainly do remember that picture and that whole thread. It's one of the threads that got me thinking about chain adjustment at the outboard end of the mill. The last sentence in that thread is me saying "Double ender sounds like the way to go though. I might just make my own ?" I would have made this mill earlier if I had not been away between April and August of this year, and come back with mangled fingers!!

Regarding harmonic resonance tearing things apart, I'm familiar with this as I teach this stuff at work. It's usually not that hard to deal with provided one can see the onset occurring and some adjustment or variability is designed into the system. In this case it should be a matter of just changing the springs or arrangement of springs, like putting another smaller spring inside a bigger spring

With long bars I run the chain quite tight but I always worry about it being too tight and about the high strain regular chain adjustment places on the relatively small chain tensioner. With this new setup, and whether I do or do not use the springs, I should now be able to set the chain tension accurately and reproducibly using a cordless driver ie set the clutch at the required setting and run the driver until the set clutch engages.

It's gonna still be a while before I can try it out because I still have to make the inboard end of the mill and the amount of time I have to put towards it is going to be small.

Surely if its a harmonic vibration problem you can alter its resonant frequency by changing the weight of the bolt?

 

[BobL]

Surely if its a harmonic vibration problem you can alter its resonant frequency by changing the weight of the bolt?

I'm bot sure what bolt you are referring to?

My biggest concern is the possibility of the chain (and thus the sprocket) resonating with the natural frequency of the springs.Iif that happens the amplitude of the vibration will increase and who knows what will happen.

There are a couple of options to minimize this, change the weight of the sprocket (ie difficult) or change the springs. Adding a damper between the sprocket and the A frame is another possibility.

I did a bit more this evening but no time for any photos. Mainly stiffening the A frame on the nose end of the mill and added some brass angle to cover the exposed part of the A-frame so when the chain comes off the cutters hit brass and not steel.

 

[Daninvan]

Bob,

Very inspiring work as always! Keep those pictures coming, enjoy seeing the progress and the thinking that goes into it.

Cheers,

Dan

 

[demographic]

I'm bot sure what bolt you are referring to?

My biggest concern is the possibility of the chain (and thus the sprocket) resonating with the natural frequency of the springs.Iif that happens the amplitude of the vibration will increase and who knows what will happen.

There are a couple of options to minimize this, change the weight of the sprocket (ie difficult) or change the springs. Adding a damper between the sprocket and the A frame is another possibility.

I did a bit more this evening but no time for any photos. Mainly stiffening the A frame on the nose end of the mill and added some brass angle to cover the exposed part of the A-frame so when the chain comes off the cutters hit brass and not steel.

Sorry, I was looking at it the wrong way there and thought the bolt was attached to the sprocket and the spring pulled from the other end.

My mistake.

 

[BobL]

Bob,

Very inspiring work as always! Keep those pictures coming, enjoy seeing the progress and the thinking that goes into it.

Thanks Dan, I had the idea half baked back when I caught up with you in BC, but until I actually make it I often can't explain it.

 

[BobL]

Finished the chain connected all thread rods this evening. It works nice and smooth. It will be interesting to see how much the chain rattles when the power head is running.

I'll start on the inboard saw holding end tomorrow - I'm still unsure what I'm gonna do.

 

[BobL]

*** WARNING - SUPER GEEKY CMS STUFF - ***

Some more pics of the new mill.

and here's the BIL mill with the 076 for comparison.

If you can see a certain common style with the BIL mill, you're right, I collect bicycle parts and use handlebar stems on lots of stuff as they make good handles.

The main difference between the saw mounts is the new mill has no cross piece between the uprights near the saw. Together with a modified saw mounting position (see below) this means the saw can sit a little more forward in the mill to maximise the cutting length, (I didn't completely maximise this on the BIL mill)- in the case of the 076 it's only about 1.5" more forward but it means the wrap handle won't interfere with a standard cross piece. In the case of the 880 it will be a little more that the BIL mill - see below.

Here's a side view of the saw mount.

The main connection point is that piece of blue 1 9/16" SHS with holes drilled in it on one side that are just the right size for the 10 mm bar bolts and 7/8" on the other to allow bar nuts and a socket to pass through the hole. The SHS is welded to the 3/16" angle cross bar that connects the bottom of the two inboard uprights. I'm using nuts with a built in washer so they sit on the end of the long socket that can drive and tighten these nuts in thru those big holes. The idea of using SHS as a tall standoff I shamelessly stole from another member on this site, I can't remember who your are, - sorry or I would have acknowledged you.

One reason for having such a tall standoff is that this allows for good clearance between the wrap handle and the mill because my chains go over the top of the saw/bar at the outboard end and under the saw at the inboard end. This means the chain crosses the saw near the inboard uprights so good clearance is needed between the inboard uprights and the saw.

Here's another view showing the clearance.

Yeah I know I need a new sprocket!

Here's a front view.

The first thing a log will now normally hit is the casting that supports the 076 chain brake handle circled red in the picture above. To reduce this effect I will add a skid at that point as well as adding some wheels. Tensioning the chain on the outboard end means the bar can be run at it's full length so the theoretical max cut from the 44" bar is 42.7". I though the to and from rocking flex would be noticeable with such as setup and I was all ready to gusset the SHS to the mill but that is not necessary. The powerhead does flex up and down much more than I like and will have to attend to that.

One thing I wanted to do was make the new mill able to take the 076 and the 880 without any adapters such as I use on the BIL mill, which was originally made to suit the 076, but needs an adapter plate to take the 880. The reason for this is their bar bolts are located in slightly different positions relative to the front of the saw and the built in chain break handle makes the 880 taller which means it hits the mill BIL mill upright which means on the BIL mill the 880 has to sit further away from the uprights resulting in reduced cutting width.

The new mill is wider and there is no cross piece to interfere with the 880 chain brake BUT the chain brake makes the 880 taller so it also has to sit further back in the mill away from the operator. This means the ideal mounting point is different than that for the 076 (DANG!). I mucked about with it all day yesterday trying to get a compromise but I have decide to settled for using two completely separate mounting cross bars - one for the 076 and one for the 880 - I can do this because the new mill is bolted together - if it was all welded I'd have to settle for an adapter plate and a reduced cutting length for the 880

 

[Brmorgan]

Looking pretty sweet, Bob! But I'll be honest, my back is getting sore just looking at that!

 

[BobL]

Looking pretty sweet, Bob! But I'll be honest, my back is getting sore just looking at that!

I thought it would be really really heavy but I am quite surprised at what it weighs. I reckon it's about as heavy with the 44" bar as the BIL mill is with the 60" bar. But I still have stuff to add like the Aux oiler, wheels and feet - although those will be made of plastic.

I have to keep reminding myself it's a test bed for ideas. So far it's cost me less than $50 and I have learned quite a lot from the exercise and had a lot of fun and some frustration making it. If I decide to keep it as a working mill I would do things like cut those C-sections in half, and spend $20 and swap the 3/16" angle for 1/8" and the 1.5" x 3/16 strap for 1" x 1/8 strap. It could even be 90% useable?

But the most likely thing is I will spend $50 on some 1/4" Ally angle and strap and buy a carton of beer and go visit BIL to weld up the ally and strap and It will then be about the same weight at the BIL mill.

More posts soon - working on the wheels - just about done.

 

[BobL]

Wheels 3

I've been messing with ideas for wheels for days and finally decide to keep them simple and see if they work.

The wheels are from a foot powered child's 2 wheeled scooter so they are bigger than roller blades but you can see one of these is not too round (obviously the kid applied the brakes a bit hard a couple of times) but I'll see how they go and the next time there is a kerbside trash pickup I'm sure I'll find another set or sets!

The wheels are mounted on the blue 7" long 3/4" SHS. The end opposite the wheel is plugged with a 1" long square cross section piece of steel that fits neatly inside the SHS and is locked into place by welding the exposed end. A 1/2" diam hole is then drilled thru the side of the plugged end. A single end hinge is made from a 1/2" round solid steel rod and a short piece of 3/16" strap. The plugged end of the SHS has a threaded 1/4" hole that takes a locking screw.

The wheel are located in the same plane as the bar and can rotate about 270 degrees (although only 120º are of some pratical use although the remaining rotation gets them out of the way) but cannot rotate to come any closer than about 5 " from the chain. They cover a range of ~8" and seem strong enough but only using them will tell.

Here's a shot of the nose I took the other day and forgot to post.

The brass angle is to protect the chain when it comes off so that the chain attacks the brass instead of the steel. The aux oiler point is made from irrigation fittings, some brass rod and stainless strap. The vibe will probably spray oil all over the place so I might have to stiffen up the SS or make the C-shape a bit smaller.

 

[betterbuilt]

Looking at the pictures I was trying to figure out how the wheels adjusted. It looks like they just swivel. Do you have a way to hold them in a specific position. I like the simple design. nice.