cable drum RPM's

[NMFP]

Converting the handset belt feed over to hydraulic feed, what is the target rpm that the cable drum should maximally rotate at?  I have sawn on numerous circle mills but never calculated the rpm rotation of the cable drum.

Trying to figure out my gearing ratio from my hydraulic motor to the cable drum is why I ask.

Thanks for the help in advance.

[Jeff]

depends on the diameter of your drum.

[DMcCoy]

C=D x 3.14
Measure the diameter of your drum add one(1) thickness of your cable to this measurement x 3.14 = the distance you carriage will travel per revolution.  You have 2 cable thickness but the centerline of the cable is what you use so 1 cable thickness will give you the number you need.

The feed rate is determined by the depth of cut per tooth you want, and saw speed.

[bandmiller2]

I  would make a mark on your drum without the cable and count the revolution in one minutes time with the Frick feed and figure close to that. One of the advantages of hydraulic feed is the ease in changing it with an adjustable needle valve.  My old Chase has a friction feed, I put a four speed transmission between it and the drum light stuff I upshift, oak I drop down a gear or two. Frank C.

[NMFP]

Thanks guys for the information.  I am tryting to match the correct size hydraulic motor and sprocket combination to be realistic. 

Its funny but in all the years of sdawing, I have never once watch the speed or determined how fast my carriages were traveling, just did the job of sawing efficiently.

I am not a fan of friction drive so therefore, eliminating it and going with hydraulic feed, easier to use and is easier to control in my opinion.

Thanks for the information.

[sawdust joe]

On my handset mill that I refurbished I used a hydraulic motor off of a scissor lift the one that drives the wheels,they are a bit high priced surplus center has them.
you need this type of motor low speed high torque. after motor dubble chain reduction is what I used.
I will try to get the sproket sizes tomorow.
Happy sawing be safe.

[whitepine2]

 You might think about a rotary valve rather than a push-pull type,this will
give you more control over speed also an adjustable flow control so you can gig back faster than feed and or hydraulic motor that is variable speed in reverse as found on pullmaster winches I think 3 times faster in reverse just my 2 cents worth. I been there with a Bellsaw used adjustable control and worked well. 

[Ron Wenrich]

I'm thinking its a 3:1 ratio, but not real sure.  The RPM doesn't matter, as long as you can get the feed that you need.  You just need to be able to control it from the sawyers position.  I always did that with the valve.  Gig forward and back were the same speed on the last mill. 

[NMFP]

Thanks for all the replies.

Ron, I was thinking 3:1 as well but I wasn't completely sure.  I have been looking at some very high torque motors but the rpm is about 300 rpms.  Not sure if I need to go higher or lower on the RPMs as I can change the ratio.

I have always used a limiting valve but thought I would try to get it as close as possible first before installing limiting valves.  Under normal sawing speeds, what is the average speed of a carriage?  If I can work off of an average speed, I can work everything backward and figure out which motor and sprockets to purchase.

Thanks for all the help guys.  Greatly appreciated.

[DMcCoy]

Carriage speed -Do you have a board or two laying around that hasn't been planed?  Measure the distance between repeat deeper saw marks and divide by the number of teeth to get the cut per tooth. 
Multiply the distance between these marks by saw RPM should give you carriage travel.

I went out and measured a board.  Western red cedar 7.5" wide.  Deepest tooth marks were 1.5" apart.  24 tooth saw. This gives me 1/16" cut per tooth.  Does this sound about right?  I'm in the west sawing softwoods, I have heard that eastern hardwood saws have more teeth and a lighter cut per tooth.

My saw is hammered for 600 RPM.  1/16" cut per tooth x 24 teeth = 1.5" carriage travel per revolution feed rate.  600 RPM saw speed x 1.5" = 900" or 75' per minute carriage travel.  Which sounds fast to me and I'm sure my motor didn't maintain speed but with the carriage feed works run off the saw arbor they were in sync.

As you get to start fresh I would start with the depth of cut per tooth.  Maintaining chip size is important to help keep the chips inside the gullet.

I like the idea of using a transmission to get different speeds.  Even with hydraulics I think this would be useful.

[beenthere]

NMFP
If you haven't seen this .pdf on circular saws, it may come in handy for you.

http://www.fpl.fs.fed.us/documnts/misc/circsaw.pdf

[coastlogger]

Just decide how fast youd like it to gig back,(fairly fast Id imagine)make that your calculated full speed.Sawing speed can then be anything you want,as long as its less than the gig back speed. Hydraulics are infinitely variable.I used this "theory"hen I hydraulified my Belsaw and it worked fine.

[Ron Wenrich]

Depends on what you're cutting - species, and width.  I would think you would want to go at the fastest speed for your fastest cutting, which would be white pine in your area.  I'm thinking my carriage was running about 6' per second, as I could make an 8' cut in tulip poplar in about 2 seconds.  Oak was a little slower at 3.  I'm thinking we controlled some of the speed with pressure.

Your hydraulics should be set that there is dynamic braking.  In other words, it doesn't coast when you let go of the handle.  It should stop dead. 

[NMFP]

I was thinking a maximum of 6' per second was what I would engineere for and then just adjust up to that accordingly.

What I didn't want to do was make a rocket out of the carriage and  use the incorrect gearing and have a carriage that would go at 15-20' per second.  Although I could always use a line restrictor, I would rather not do that.

Remember the old control valves that were used in circle mills?  The ones with one single handle and two control valves in the bottom with a long handle, that's what I am using for my forward and reverse control as the handle is long enough to feather it and make it work at any speed.  I will just simply unhook the one valave and use the other one.

Pump output is a little over 25 gpm so fluid flow will not be a problem at all, just need the correct size motor which I think is going to be a 153 rpm motor turning the cable drum.

Working on track construction today again and hope to have all of the bracing and track in by the end of the week.  Hopefully sit the carriage on it this next weekend and then run the cable.  Hope to have pictures soon but I haven't taken any throughout the process, more concerned about getting the job done than taking pictures but all I can say is, it will last forever as heavy as its built.  Built with all 6x6 and 4x6 pressure treated for frame work and then 5/16" thick steel channel for the tracks.

[bandmiller2]

NMFP, are you going to direct drive the cable drum with the motor or use a sprockets and chain.?? Ron mentioned it but carriage braking is an important function of the feed. Some of the guys here have gone to hydraulic I hope they chime in. It makes me nervous to think of a carriage and heavy log gigging back at a good clip and the valve just stops the motor, that will put a lot of strain on everything. Possibly an open center valve that will let the carriage coast down or feather the valve forward to slow it faster. I'am not sure on this, do the heavy commercial mill carriages stop short or do they have a soft stop. Frank C.

[NMFP]

I don't know about some, but all of the mills I have run have been controlled by hydraulics and letting off the hydraulic lever, actually brings the carriage to a stop, or if need be, reversing direction momentarily.

I plan on installing a cushion valve in the line to prevent catastrophic failures to the motor which will take the high pressure and divert it to the other side of the motor.

Any one else have experience converting a friction drive to hydraulic drive?

[Ron Wenrich]

We converted one many years ago.  It was on an old hand mill, and it was a motor with a sprocket and a chain drive.  Even the bigger commercial mills that came in hydraulic had a sprocket and chain to the cable drum.  I don't think I've seen any with a direct motor.  I'm not good enough at hydraulics to tell you how things were plumbed up.  But, all the mills I've run have stopped dead when your hands were off the controls with no coasting. 

[NMFP]

Thanks guys for the help.  Hope to have all of the framework in today and tomorrow and then put the steel track on top within the week.

Next step is the husk, but that will be simple and easy.

Thanks for all the help.

[Mooseherder]

I was working around my husk today and have some information for you.  I was going to take pictures but my phone was dead.  It keeps searching for a signal up here and kills the battery.
I have a hydraulic feed deck all steel.  The motor used to spin the cable drum shaft is called a Ross torqmotor, the part number is MB180103AAAB.
Also on the tag was.  CC.  MB.  280,      D/c 319 95 0

The chain sprocket was almost 5 inches.  It had a part number on it also.
I'll write it down if you need it.

[NMFP]

That would be great:

Here is what I have been thinking about:
Hydraulic motor shaft turns at 153 rpms
Hydraulic motor driving sprocket would have 16 teeth
Driven sprocket on the cable drum would have 36 teeth (68 rpms)
that ratio would be 2.25 to 1 meaning for ever 2.25 revolutions of the drive sprocket, the driven sprocket will turn 1 time

My cable drum has a diameter of 14" to if I use C=2pie *r
      2*3.14*7= 43.96" travel per revolution or 3.66' travel per drum rotation

68 rpms x 3.66' = 248' of travel per minute
248' / 60 seconds per minute = 4.13 feet of carriage travel per minute.

Is 4.13 feet of travel per second too slow?  All of the mills I have sawn on both commercially and at the school I teach at turn at 650-750 rpms.. The blade I am running will be turning at 550 rpms and is 48" diameter.

I feel this will work, but looking for other peoples ideas as well.

Thanks everyone for your comments and ideas!

[Ron Wenrich]

I think you mean 4.13 ft per second.  Seems a little slow, especially on the gig bag.  You might need a faster motor.

What kind of speed does the mill at the school have? 

[NMFP]

Ron, yes, you are correct.  Typo I didn't see before I clicked post. 

I don't know what motor is on it as I have checked it out and there are no tags attached to it.  I do know that system is designed with a 75 gpm pump which is rediculasly high but it work well as we have numerous things running hydraulics at the same time.

I think I am going to run over there and mark the drum and find someone to run the carriage back and forth and ill count the revolutions and time it as the carriage is running back and forth.  I just want to make sure I am not building a rocket or a turtle is my concern.

Some of the books I have read over the years go into carriage travel and the one says the average bite per second should be approximately 4.5" per revolution of the saw. 

Think I will look for a slightly faster motor and see what I can find.

Thanks Ron!

[bandmiller2]

A couple of things to consider with feed rates is the HP available at the saw. The ideal feed rates assume you have enough power. Also sawyer skill, myself I don't like things happening too fast, a young fulltime sawyer can handle more feed than a part time duffer. Frank C.

[NMFP]

Agreed.  Its interesting that so many are rushing to purchase bandmills but yet, there are numerous of us out there that are rebuilding old circular mills due to production requirements.  Speed of sawing on my bandmill is slow compared to what I am used to so maybe when I get older, I may regress back to the bandmill.... who knows though.  Need to get production through and at any speed, the circular mill will be much faster than the band mill.

Hp for the mill I am building will be about 185 hp air cooled deutz air diesel... Only thing running off of it would be the arbor and the hydraulic pump so there should be plenty of power to saw at most speeds.

[Ron Wenrich]

We were running a 75 GPM pump just for the feedworks.  We used another 50 GPM pump for the rest of the hydraulics.  We needed a cooler on the oil tank in the summertime.  We had a Jackson Lumber Harvester portable that used a lot less than that, and fed pretty well.  I think their hydraulic system might be one to look at, as it is small and simple.  The carriage was very light, and ran on bearings instead of a track.  I really liked that mill.

As I got older, my production rates went down.  Part of it was due to my crew getting older, as well.  Ideal feedrates also implies ideal logs and conditions.  As the edge comes off your teeth, that ideal condition no longer exists.  You can feed at that ideal rate, but your lumber quality will suffer.  Same goes with crooked logs or logs with excessive knots.