Alaskan Mill w/ 4 stroke engine vs chainsaw

[dcg4403]

Greetings,

I must admit that I'm fairly new to the trade so I apologize if I sound ignorant. I'm looking for some insight and ideally some design help. I'm a general all around gear head with have access to a machine shop and am a pretty good TIG welder.

I've been eyeing alaskan mills for some time for the purpose of slabbing out 30" - 48" logs for my furniture business. I was originally after a Stihl 090 but the prices are pretty steep for this vintage saw and most are beat up, yet, selling for $1500+. I did manage to find a completely restored McColluch SP125 for $825 but it is so nice I'd hate to use it! I need to be able to slab out up to 50" diameter logs.

Anyway, I was thinking that it would be of better value & power to use a 18-21 HP vertical shaft 4-stroke motor with the proper pulleys to achieve the ideal rpms (8-10K from what I've researched). Around a 500 cc motor.

Has anyone build one on an alaskan mount?

I do understand one major downside is the overall weight. Probably talking 100-120 lbs alaskan mill vs 40-60 lbs. However, with a two man crew, this isn't a major issue for me. Plus, I need the weight lifting exercise!

Any help or advice is much appreciated. I'd rather not re-create the wheel.

Devin

 

[dcg4403]

I'm making some progress but am still looking for any pointers. I know I'm not doing anything new here outside of maybe being insane enough to desire a 4-stroke mount alaskan setup!

I'm thinking about a centrifugal clutch setup. I'm not aware of any downsides? One big upside is that I can idle my motor (when resting) with no chain movement.

1) For mount onto the 4-stroke vertical shaft, I'm looking at the Heavy duty single groove clutch with 4” belt pulley, for 1” shafts on engines up to 20 HP from Linn Lumber.
http://www.linnlumber.com/page6.html

2) On the bar side, I'm looking at Harvester rim sprockets with 1" bores. I'm just not sure about # of teeth. 10, 11 or 12?

3) I have no clue what I'm going to use between the rim sprocket and Linn clutch. I know I need at least a 2:1 drive so I can make sure I'm closer to 8K rpms. I still need to identify a two groove pulley with the right diameters for the final drive ratio.

Can anyone tell me how to calculate chain speed or final RPMs? What I'm clueless about it mostly related to sprocket teeth count.

Devin

 

[BobL]

I I'm thinking about a centrifugal clutch setup. I'm not aware of any downsides? One big upside is that I can idle my motor (when resting) with no chain movement.

I wouldn't call it an up side - I would call that essential or it will make a mess of the finish.

3) I have no clue what I'm going to use between the rim sprocket and Linn clutch. I know I need at least a 2:1 drive so I can make sure I'm closer to 8K rpms. I still need to identify a two groove pulley with the right diameters for the final drive ratio.

As a guide I would look at Lucas mill slabber specs for chain, drive sprocket size and RPM.

Can anyone tell me how to calculate chain speed or final RPMs? What I'm clueless about it mostly related to sprocket teeth count.

chainpitch(inches) * 2 *rpm*DTC/12 will give you the chains speed in feet per min.

DTC = Drive sprocket tooth count

All chain based milling is "chain limited" so although you will have brute power the limitation you will face is the ability of the chain to bite wood and clear chips. Developing the skill of filing a chain to suit your particular setup will be crucial otherwise you will be no faster than a regular chainsaw. This is something you will have to get the feel for yourself so it won't happen overnight. You will also need to bone up of progressive raker depth setting. The Lucas mill slabber people use 404 chain with low rakers.

Don't be surprised if after all this you are only marginally faster than a big chainsaw.

 

[dcg4403]

BobL,

Thanks for the input.

So the engineer in me ran all the numbers. I think I've got a good plan of attack.

• Using a 21 HP B&S vertical engine with a 1 bore shaft
  • Max is 3300 governed RPM
• Mounting a centrifugal clutch rated up to 25 HP to the vertical shaft. Dual groove pulley to ensure the belts don't slip.
  • 4" OD on pulley (all my calculations are consistent with ODs vs Datum diameters)
• Dual grove pulley with 2.0" OD.
  • Drive ratio at this point = 2.0
  • 3300 RPM at engine shaft = 6600 RPM at pulley
• Using a 3/4" bore (keyed) torsion shaft from 2" pulley to straight bore chain sprocket
  • 11 tooth sprocket at 6600 RPM = 49.7 MPH chain speed
    
  • 12 tooth sprocket at 6600 RPM = 54.7 MPH chain speed
    
  • 13 tooth sprocket at 6600 RPM = 59.8 MPH chain speed
  • 14 tooth sprocket at 6600 RPM = 64.9 MPH chain speed

I've read conflicting information about chain speeds. Some claim as low at 40 MPH while others up to 65 MPH. What is optimal for a slabber? I was targeting either a 12 tooth or 13 tooth sprocket at 55-60 mph.

As BobL noted, chain speed is not my only determining factor in my feed rate. My 21 HP motor will generate at least 16.7 ft/lb of torque at an equivalent of 6600 RPM. For reference a stock Stihl 090 generates approximately 7.2 ft/lb at 6600 RPM. None of this accounts for frictional loses but are very close to real numbers. So I'm looking at about 50% more torque than the 090.

I may actually go to a small motor to help reduce some weight. Maybe a 15 HP. B&S doesn't rate torque numbers on their bigger motors. But a 22HP kohler is rated at 44 ft/lbs (I calculated 33.4 ft/lbs for the 21 HP B&S). So 21 hp is a lot more power than I'll need. Like to be at least 30% better than a 090 chainsaw.

 

[BobL]

Another comparison you might like to make with harvester hydro packs.
Harvester hydraulic motor RPMs start at around 12000 rpm (max) 8000 rpm continuous, 4ft/lb torque and 30HP (20 HP continuous) for baby sized trees, through to 4500 rpm (max) 3600 rpm continuous, 60ft/lb torque and 160HP (135 HP continuous)

If it was me I'd be aiming for a maximum chain speed of ~65 mph but sprockets greater than about 10 teeth can't be used safely on conventional CS bars so you'll have to regear and maybe look at harvester bars.

 

[chads]

I'm guessing here but I'd rather slow the rpms on a bigger motor and up the pulley size a bit.
Save the headaches from a loud motor.
I would look at real weights before changing size.
they may be close.

 

[BobL]

I'm guessing here but I'd rather slow the rpms on a bigger motor and up the pulley size a bit.
Save the headaches from a loud motor.

Good point.
Even with two people I can't imagine lifting a kohler on an off a log all the time.

 

[dcg4403]

Thanks BobL and Chad.

Regarding, Bob's comment about "If it was me I'd be aiming for a maximum chain speed of ~65 mph but sprockets greater than about 10 teeth can't be used safely on conventional CS bars so you'll have to regear and maybe look at harvester bars."

I didn't know this although that's true for many things related to milling at the moment! I'm assuming this is due to the overall diameter of a 10+ tooth sprocket and the increase width of harvester bars?

Stupid question, is there a correct name for a standard guide bar (non-harvester) that are common on most chainsaws?

I'm going to put a call into Danzo on Monday to get their advice since I was eyeing their sprockets. I'm sure they've provided sprockets for similar setups.

I'm hoping to get pictures of the drive system from either a Lucas or Peterson slabber. If anyone has one, I'd really appreciate detailed photos. I know Lucas runs a 5" OD centrifugal clutch w/ V belt. Just not sure how they are driving the chain.

Devin

 

[JakeG]

If I were to build something similar, I'd build a carriage for it to ride on. Great idea btw and I hope you give it a shot. You could to even smaller on the engine. Think Honda maybe

 

[Jimmy in NC]

Interesting project. Curious how this is going to turn out.

 

[dcg4403]

JakeG,

Yes, I'm actually thinking about a simple and portable carriage system. Or at least building the powerhead setup to work well with a carriage. Like it to be versatile as an Alaskan mill but also configurable to a carriage like a Lucas mill. I should be CADing the design soon. Still trying to work out the drive setup kinks.

Outside of harvester bars or deck bars, can anyone point me to a wider style bar that will be compatible with a 12-13 tooth sprocket? I don't want to run a 3/4" chain. I was originally wanting to purchase this but am worried a 12-13 sprocket is too large of a diameter so the chain won't ride correctly on the bar. Here is the style of bar that I'd like to run:

http://leftcoastsupplies.com/product/72-gb-double-ended-guide-bar/

 

[bleoh]

If I were to build something similar, I'd build a carriage for it to ride on. Great idea btw and I hope you give it a shot. You could to even smaller on the engine. Think Honda maybe

I saw this video and thought that a cheep vertical engine from a lawn/riding mower could be put to good use. Although I am not sure how much more it would take to make a band saw mill.

 

[ILikesEmGreen]

I guess in theory you could put a bigger pulley wheel on the shaft and run a band blade off it. A bit more to design the other end and get it all lined up, but possibly cut better and more efficient.

Sent from my C811 4G using Tapatalk

 

[BobL]

JakeG,

Yes, I'm actually thinking about a simple and portable carriage system. Or at least building the powerhead setup to work well with a carriage. Like it to be versatile as an Alaskan mill but also configurable to a carriage like a Lucas mill. I should be CADing the design soon. Still trying to work out the drive setup kinks.

Outside of harvester bars or deck bars, can anyone point me to a wider style bar that will be compatible with a 12-13 tooth sprocket? I don't want to run a 3/4" chain. I was originally wanting to purchase this but am worried a 12-13 sprocket is too large of a diameter so the chain won't ride correctly on the bar. Here is the style of bar that I'd like to run:

http://leftcoastsupplies.com/product/72-gb-double-ended-guide-bar/

The problem with all these bars and large sprockets is the ends taper too much and if a large sprocket is used and the chain becomes a tad slack then as it is pulled around the sprocket it may not find the bar groove and it will jump the bar. This is even more of a problem with the bar laying on its side.

You have a couple of options
1) cut the bar end to suit and mill a longer slot for the bar bolts and then weld a new piece in the open slo.. The bar oil hole is not needed if a convention aux oiler is used. If this is rigged carefully the bar temper should not be affected

2) Ensure chain tightness at all times.
Back in 2010 I built a chain tensioning device located on the outboard end of a nose bar based on valve springs that took up the slack as the chain heated and expanded.
I have some photos f it - I have never tried this out so I don't know if it works.


The brass angle is sacrificial surface in case the chain comes off


Here's the updated spring retained


Here is what the mill looked like.

 

[firebrick43]

BobL, As a machinist and mechanic, I must say you do very nice work. Its not scabbed together like alot of other homemade stuff.

I do have a huge request however. Would you be so gracious to reload some of the pictures to the BIL Mill Threads as when the site crashed they were lost. I would be greatly appreciated by many I do belive, even if its just 4 or 5 shots of the overall setup at the end of the thread.

Thank you

 

[JakeG]

BobL, As a machinist and mechanic, I must say you do very nice work. Its not scabbed together like alot of other homemade stuff.

I do have a huge request however. Would you be so gracious to reload some of the pictures to the BIL Mill Threads as when the site crashed they were lost. I would be greatly appreciated by many I do belive, even if its just 4 or 5 shots of the overall setup at the end of the thread.

Thank you

I second this request

 

[dcg4403]

BobL,

Very, very nice. It appears that you used a modified sprocket nose with a standard GB bar. You drilled a mounting hole at the outboard end of the GB bar to ensure alignment to the sprocket nose? Wonderful approach and adds additional length. Love it!!!!

Great advice on cutting off the inward end of a bar. I really like that suggestion. Do you have any recommendations on how to properly cutting the end? I have a 3-phase cold saw and portable Jepson cold saw but would be fearful they would not cut a hardened chainsaw bar. I'd hate to ruin my saw blade teeth considering my blades run about $300/each. I do have a portable DeWalt metal bandsaw.

I agree with FireBrick that it looks very professional. I TIG weld almost everything I do and run Bridgeports for machining my parts, so I hope to hold the same quality level!

The use of a valve spring is ingenious. My research has shown that you need to maintain 120 lbs of tensile force on the chain (or compression on the bar) to ensure it remains in proper tension. I haven't researched springs but do happen to have several valve springs sitting around. Never would have thought of that solution. Great stuff.

And nice use of brass!

Thanks so much for sharing those pictures. Once I start my build, I will be sure to post pics. So many discussions about this type of build but few people is seems actually end of building them. I have a 5 foot pecan waiting for me so I need this mill by end of April.

If anyone has a Lucas or Peterson slabber, I'd love to see pictures of the inward and outward drive and mounting of that setup. I'm curious how they approach it.

Devin

 

[firebrick43]

I would use a abrasive cut off saw or abrasive blade in a 4" angle grinder. Just go slow and quench often to keep from taking the temper out of the steel.

 

[BobL]

Firebrick and Jake, I will reload the pics for the whole Mill BIL thread - although I have retired from the day job I am busier than ever!

One morning a week I'm supervising a bunch of about a dozen vets doing some basic woodworking. The guys are aged 76 to 96 and most are handicapped in one way or another. Nearly all have suffered a stroke victims. Only 2 have use of both hands, 2 cannot speak at all, and 4 are totally incapacitated and are in wheelchairs. Most of the time I'm the one doing the woodwork and there's lots of comments, reminiscing and stories.

Two half days a week I am helping a local "Mens Shed" set up tools and machinery for their new shop. "Men's Sheds" are a not-for-profit organisation across Australia that sets up community workshops so that (mainly retired) men or men without a home shop can meet regularly to work on projects individually or in a group, or just socialised in a male environment. In Australia they have been recognised as helping fight Depression in older men. Funding comes from local and state government and other charitable agencies. Current our group has about 20 members and is operating out of the shops in a local high school but they have funding for a large shop attached to a local senior citizen centre. They have obtained donations of lots of old hand tools and machinery so they need help in sorting these out - kinda right up my alley.

 

[BobL]

Very, very nice. It appears that you used a modified sprocket nose with a standard GB bar. You drilled a mounting hole at the outboard end of the GB bar to ensure alignment to the sprocket nose? Wonderful approach and adds additional length. Love it!!!!

Thanks. It doesn't add any length to the nose bar holding systems I use on CSMs as the mechanical bits get in the way of the cut

Great advice on cutting off the inward end of a bar. I really like that suggestion. Do you have any recommendations on how to properly cutting the end? I have a 3-phase cold saw and portable Jepson cold saw but would be fearful they would not cut a hardened chainsaw bar. I'd hate to ruin my saw blade teeth considering my blades run about $300/each. I do have a portable DeWalt metal bandsaw.

I agree with firebrick. Thin kerf cutting wheel and stop and quench on a regular basis. I have an old woodworking table saw that I run 5" thin kerf cutting wheels in and I have a drip feed water cooling system that I use to cut tool steel with without affecting the temper.

I agree with FireBrick that it looks very professional. I TIG weld almost everything I do and run Bridgeports for machining my parts, so I hope to hold the same quality level!

Although I have access to all sorts of shop gear at work (or more correctly where I used to work - one of my retirement presents was the keys to that workshop!!!) I try to do everything in my home shop. I usually just use my welder in stick mode and although I have no metalworking mill I do have a small Southbend lathe which I find quite useful. I also just built myself a mains gas fired forge which I am hoping to do a nit of smith sop work in.

The use of a valve spring is ingenious. My research has shown that you need to maintain 120 lbs of tensile force on the chain (or compression on the bar) to ensure it remains in proper tension. I haven't researched springs but do happen to have several valve springs sitting around. Never would have thought of that solution. Great stuff.

Thanks for the lead on the tensile force - I will measure this on a set of scales and that will tell me roughly what compression I will need on those springs and if they are too weak I will have to find stiffer springs.

And nice use of brass!

Thanks. My other big mill is made almost completely out of Al and that has saved many a chain.
I like using brass and use it often in my woodwork tool making. Here is an example in the handles of a couple of Japanese saws.
Wood is home milled Apricopt.

Thanks so much for sharing those pictures. Once I start my build, I will be sure to post pics. So many discussions about this type of build but few people is seems actually end of building them. I have a 5 foot pecan waiting for me so I need this mill by end of April.

Looking forward to seeing the build.