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Firewood processor design trouble

Started by Demetrio, May 15, 2020, 09:35:17 AM

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Demetrio

Hi there!

First of all, let me introduce myself.

I`m Demetrio, 27 years old, from northern Italy. My family has a small farm, even if it's not a full time job. We grow mainly poplar trees for the paper industry. We used to grow corn/rice/wheat/sojia but it's a lot of work if you have only week ends, while growing trees is easier. Been on tractors since I was 7, including chainsaw work (I started that later) and gardening work. Chainsaw work is necessary since we have a quite big house with a heating system which is fed with firewood. Here we mainly burn black locust, oak and poplar, log size is rarely > 30'' (very rarely 40'').

I was planning to build a firewood processor to unburden my father back; he's getting old and I have less and less time to help him with firewood (I do not live with my parents anymore). That being said I would like to share with who's interested some ideas/doubts and to get some advices from people who knows surely better than me.

My plan was to use the tractor rear PTO as power source; than I would have a gearbox (ratio 1:3) to increase the output shaft speed to which a single stage gear pump is connected (something around 23gpm at 2800 rpm, 33cc of displacement, max pressure is around 3500psi). The cutting is performed by a hydraulic motor (gear motor, around 4000rpm with 23gpm, 20cc of displacement) powered chainsaw. This configuration would provide a chain speed of 75 feet/s considering a big enough chain sprocket (4'' diameter). For the log splitter I was planning to use a 4'' bore cylinder which would provide a 20 tonnes force (considering 3500psi). Biggest logs are cross split, while logs under 10'' are half-split. Cutting length has to be around 20''.

Let's start with the frame.
First obstacle is the log conveyor. I initially sketched a frame for a roller log conveyor (see attached sketch); then, for simplicity, I changed my mind towards a chain conveyor (see sketch). Indeed, there's quite a bit of cutting/welding work to make the rollers, while it seems easier with chains. Moreover I might recover 2 hand chains from combine harvesters for free from a friend. Sketches below are only drafts (incomplete); my constraints are the wheeled frame I already have (see pics) and the steel beams which I already have too (H beams and C beams). Also, I think that it is easier to power one single chain running along the conveyor rather than a bunch of rollers. But then you have to consider that crooked logs migth stall with a chain, while maybe they won't with rollers. My idea was also to cut more than one log at a time, if they're small enough. What about two chains running in parallel and being clamped together with some protruding mounts which can grip onto the logs? what cross section shape is best fo the conveyor? V shape, U shape with flat bottom, flat only? Also, what is the clamping system (to clamp the log prior cutting) in your opinion? I would really appreciate if someone has some experience/advice to share. In the next days I'll try to see what size are the chain I can get. To give you an idea the frame in the sketches is 10 feet long.

Sorry if I made some mistakes with the unit measures, I'm not used to the imperial measure system! :laugh:

Cheers

Demetrio





 

 


 

 


 

doc henderson

Welcome Demetrio.  I think many will start to chime in in a bout 8 hours or so.  work day just started here.  some may jump in sooner.  looks like a neat project.  not my expertise.
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

jmur1

Hi Demetrio:

I made my processor with live rollers and a 10 foot belt at the saw end.  I have lately been cutting longer logs (almost 28 feet) and have started breaking the standard 40 chain that powers them.  I can only say build it about 3x stronger than any calculations say you need to.

I agree that chain is a good infeed method but dont go light on it - you will be replacing it.  
I will give a summary of my findings when I get some time to detail them.

Your designs look good - keep us posted!

jmur1
Easy does it

hedgerow

Demetrio  Welcome to the forum. I built a homemade processor around five years ago. I have been making changes to it ever since. I use live rollers that are big chain sprockets for the conveyor. It works ok but crooked logs are always a issue.Look at Multi tech over head shuttle that sides the logs ahead. I use a hyd chain saw I built but you end up with a lot of money in a hyd saw. Search the forum and U tube for BT-6870 fire wood processor to see a simple processor that works good without a bunch of hyds. Build it at least three times heavier than you think it needs to be. Processing wood is hard on equipment and people.  

Demetrio

Thanks everybody for the advices and for welcoming me! I approve the philosophy of building it 3 times stronger than the worst case scenario calculations say, that's the reason why old equipment still runs strong!

Quote from: hedgerow on May 15, 2020, 11:24:00 AM
Demetrio  Welcome to the forum. I built a homemade processor around five years ago. I have been making changes to it ever since. I use live rollers that are big chain sprockets for the conveyor. It works ok but crooked logs are always a issue.Look at Multi tech over head shuttle that sides the logs ahead. I use a hyd chain saw I built but you end up with a lot of money in a hyd saw. Search the forum and U tube for BT-6870 fire wood processor to see a simple processor that works good without a bunch of hyds. Build it at least three times heavier than you think it needs to be. Processing wood is hard on equipment and people.  
@hedgerow  I checked the BT-6870 firewood processor, that's a nice piece of equipment, strong and smart (and cheap!)

Quote from: jmur1 on May 15, 2020, 10:39:52 AM
Hi Demetrio:

I made my processor with live rollers and a 10 foot belt at the saw end.  I have lately been cutting longer logs (almost 28 feet) and have started breaking the standard 40 chain that powers them.  I can only say build it about 3x stronger than any calculations say you need to.

I agree that chain is a good infeed method but dont go light on it - you will be replacing it.  
I will give a summary of my findings when I get some time to detail them.

Your designs look good - keep us posted!

jmur1
@jmur1 Thanks, I'll try to not save on steel to keep everything strong!


I'll keep you guys updated!

Demetrio

Gearbox

Hello and welcome . I am the guy that built the BT6870 . It is getting a splitter rebuild this summer .The splitter was a little slower than the 394 Huskvarna [about 4 seconds ] got a new cylinder with a 3 inch rod .By the calculator it should be at 7 seconds for a 24 inch cycle . The push plate feed works well if your logs are some what  the same length . Oil tank Make sure you use a big enough tank for your future pump needs . One gallon of tank for each gallon of pump flow . Go big on the tank more oil will run cooler .
A bunch of chainsaws a BT6870 processer , TC 5 International track skidder and not near enough time

Demetrio

Quote from: Gearbox on May 15, 2020, 08:40:52 PM
Hello and welcome . I am the guy that built the BT6870 . It is getting a splitter rebuild this summer .The splitter was a little slower than the 394 Huskvarna [about 4 seconds ] got a new cylinder with a 3 inch rod .By the calculator it should be at 7 seconds for a 24 inch cycle . The push plate feed works well if your logs are some what  the same length . Oil tank Make sure you use a big enough tank for your future pump needs . One gallon of tank for each gallon of pump flow . Go big on the tank more oil will run cooler .
Hi @Gearbox , thanks for the infos. According to my calculations, considering a 24 inch stroke with a 4 inch cylinder bore and 22gpm I would approximately have a 4s cycle. I was considering a 60 liters oil tank (16gallons) which is smaller than what you suggests (bigger tanks are pretty expensive, I need to find some second hand tank). I'll see then if there's necessity of an oil cooler.
Really appreciate the help!
Demetrio

Gearbox

speed is about trade off . 4 seconds is faster than most . that same cylinder with a 16 gallon pump would be a 13 and your tank would be good . I stayed at 16 gallons and changed out the cylinder to a 4 inch with a 3 inc rod and went from 13 to 7 seconds . A 7 seconds I have to enclose my cylinder from the push plate back . The return speed is 2.3 seconds if something falls behind the plate I would not be able to stop before it started breaking hoses and fittings . hope this helps
A bunch of chainsaws a BT6870 processer , TC 5 International track skidder and not near enough time

Demetrio

Thanks @Gearbox , you're right, compromise is very often the way to go. I'll try to keep the right scale between the pump and the tank and all the stuff depending on what I can find second hand... Maybe I can find a big enough tank from some farm equipment at a low cost. Appreciate your help!

jmur1

Quote from: Demetrio on May 16, 2020, 04:18:48 AM

Hi @Gearbox , thanks for the infos. According to my calculations, considering a 24 inch stroke with a 4 inch cylinder bore and 22gpm I would approximately have a 4s cycle. I was considering a 60 liters oil tank (16gallons) which is smaller than what you suggests (bigger tanks are pretty expensive, I need to find some second hand tank). I'll see then if there's necessity of an oil cooler.
Really appreciate the help!
Demetrio
Hi Demetrio:
When you wrote 4s cycle did you means 4s for extension time?.  I think you are nearly double that for a full cycle.  And if you are using a two stage pump it will be slower than that based on other losses (fittings, valves, filters, friction, hp).
Just wanted to make sure we were comparing the same things!
jmur1   
Easy does it

doc henderson

i think that hydraulic tanks can be confusing.  there is a total volume and a functional volume that is less.   i have a 26 gallon that holds 19 to show full on the sight glass.
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

Demetrio

Quote from: jmur1 on May 22, 2020, 02:13:49 PM
Quote from: Demetrio on May 16, 2020, 04:18:48 AM

Hi @Gearbox , thanks for the infos. According to my calculations, considering a 24 inch stroke with a 4 inch cylinder bore and 22gpm I would approximately have a 4s cycle. I was considering a 60 liters oil tank (16gallons) which is smaller than what you suggests (bigger tanks are pretty expensive, I need to find some second hand tank). I'll see then if there's necessity of an oil cooler.
Really appreciate the help!
Demetrio
Hi Demetrio:
When you wrote 4s cycle did you means 4s for extension time?.  I think you are nearly double that for a full cycle.  And if you are using a two stage pump it will be slower than that based on other losses (fittings, valves, filters, friction, hp).
Just wanted to make sure we were comparing the same things!
jmur1  
Hi @jmur1 , I meant 4 s in total, extension + retraction. Retraction is of course much faster since the cylinder chamber volume is lower due to the rod volume. For now I'm sticking to a one stage pump; cycle length calculations are based considering that all the pump flow rate is used for the log splitter cylinder (also, I need to consider the pressure drops/energy losses along the path). Power is not a big deal, I can use a 100hp tractor to power the thing (I think that 50hp are more than enough).
@doc henderson Thanks for pointing that out! I would say that tank volume has to be rougly 30% than the oil volume inside to account for volume changes due to temperature.
Appreciate you help guys! I'll soon update you!

jmur1

Hi Demetrio:

Volume of cylinder =πr^2 x h  = 300 in^3 which is total volume of cylinder oil to pipe in for 1 stroke.  (Note the backward n is a pie for the volume)
convert to 1.3 gallon of oil.

divide that by 22 and get .06 of a minute and times by 60sec/min to  get 3.6 seconds.  That is for the out stroke only.
Wouldnt be the first time if the mistake is on my side!  Let me know how you calculated it.

jmur1
Easy does it

Demetrio

Quote from: jmur1 on May 23, 2020, 10:05:44 PM
Hi Demetrio:

Volume of cylinder =πr^2 x h  = 300 in^3 which is total volume of cylinder oil to pipe in for 1 stroke.  (Note the backward n is a pie for the volume)
convert to 1.3 gallon of oil.

divide that by 22 and get .06 of a minute and times by 60sec/min to  get 3.6 seconds.  That is for the out stroke only.
Wouldnt be the first time if the mistake is on my side!  Let me know how you calculated it.

jmur1
Hi @jmur1 , that's correct! For the retraction is the same, except that the volume of the cylinder is lesser, since you have to subtract the volume of the rod! Equations follow:
Cyl_vol_extension = pi * (r^2) * h
Cyl_vol_retraction = [pi * (r^2 - r_rod^2)]  * h, where r is the cylinder radius, while r_rod is the rod radius.
So I get (I'll use dm and liters :D):
Cyl_vol_extension = pi * (1^2) * 6 = 4.71 l
Cyl_vol_retraction = [pi * (1^2 - 0.56^2)]  * 6 = 0.91 l
extension_time = Cyl_vol_extension / pump_flow = 4.71 / 1.39 = 3.4s
retraction_time = Cyl_vol_retraction / pump_flow = 0.91 / 1.39 = 0.65s
where flow is in liter/s. We have sligtly different times for the extension due to the unit measures. I used a 100 mm cylinder bore (600mm stroke) with a 56mm rod diameter. Pump flow is 22 gal/min, or 83 l/min.
I think that you weren't considering the rod volume for the retraction stroke, am I rigth? Or maybe I'm doing something wrong :-\
Demetrio

jmur1

Hi Demetrio:
I think the return stroke will be abit faster as you have calculated but dont forget you have to evacuate the opposite oil in the cylinder through your control valve as well.  This means the pump has to push that volume out of the cylinder through the control circuit and back to tank.  In my experience ths will fall somewhere in between the two calculated values.  Ill have to run some tests on my machine to back up my thoughts.  I previously had a 5" diameter cylinder that i had specially modifyied larger ram that did improve cycle time but was really noticeable after i added a piloted return line to tank.  I am now running a 4" that has a standard ram and the return is similar to the out stroke.
Jmur1
Easy does it

doc henderson

I will spare you further math on a Sunday of Memorial day.  I would say lots of people have made splitter/processors with that combo of flow rate and cylinder size.  My 28 gpm pump and 5 inch cylinder with a 1.5 inch rod, cycles fast enough that I often run it at half throttle, and it is fast enough.  you understand the variables that speed that up and the consequences of doing them.  it appears!   :)  .  I have considered a dump valve for mine, but it is expensive and will complicate the plumbing that I tried to keep simple.
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

Demetrio

Quote from: jmur1 on May 24, 2020, 07:05:57 AM
Hi Demetrio:
I think the return stroke will be abit faster as you have calculated but dont forget you have to evacuate the opposite oil in the cylinder through your control valve as well.  This means the pump has to push that volume out of the cylinder through the control circuit and back to tank.  In my experience ths will fall somewhere in between the two calculated values.  Ill have to run some tests on my machine to back up my thoughts.  I previously had a 5" diameter cylinder that i had specially modifyied larger ram that did improve cycle time but was really noticeable after i added a piloted return line to tank.  I am now running a 4" that has a standard ram and the return is similar to the out stroke.
Jmur1
Hi @jmur1 , you're making a good point, these are rough calculations and one should account for the pressure drops along the circuit which inevitably reduce the flow. But then the same applies for the extension stroke, where you have to evacuate the low pressure cylinder chamber into the tank, doesn't it? Actually I've a lot of farm equipment which uses hydraulic cylinders and I didn't really noticed such a difference between the extension and retraction strokes (I must say that I didn't pay attention to that too).
Regenerative valves seem an interesting solution! Throw a look!
If you get a chance to measure the extension/retraction stroke times let me know please!

Quote from: doc henderson on May 24, 2020, 09:05:55 AM
I will spare you further math on a Sunday of Memorial day.  I would say lots of people have made splitter/processors with that combo of flow rate and cylinder size.  My 28 gpm pump and 5 inch cylinder with a 1.5 inch rod, cycles fast enough that I often run it at half throttle, and it is fast enough.  you understand the variables that speed that up and the consequences of doing them.  it appears!   :)  .  I have considered a dump valve for mine, but it is expensive and will complicate the plumbing that I tried to keep simple.


Hi @doc henderson , thanks, I'd appreciate any sort of material you have. I'm trying to keep things simple. You can't break what is not there :D.
Demetrio

Hilltop366

There are online calculators like this one that will give you lots of info. https://www.tss.trelleborg.com/apps/hydraulic_cylinder/

Out of curiosity I put in the calculator a 4" X 24" cylinder with a 1.75" rod and a 3500 psi X 33 gpm pump. The difference in extension and retract time is less than ½ second and a 4.29 second cycle time.

A 3" rod changes it to 3.42 second cycle time with all the change on the return (rod) side of coarse. With a difference of 1.34 seconds between exertion and retract. A difference of .87 seconds between a 1.75" and 3" rod diameter.

I wonder if it would be chasing expensive fractions of a second for not much gain in processing time in the big picture, the little bit of gain in cycle time is irrelevant if you are advancing the log and starting the next cut while it is returning as long as the splitter is retracted in time to finish the next cut. 



Demetrio

Quote from: Hilltop366 on May 24, 2020, 11:17:19 AM
There are online calculators like this one that will give you lots of info. https://www.tss.trelleborg.com/apps/hydraulic_cylinder/

Out of curiosity I put in the calculator a 4" X 24" cylinder with a 1.75" rod and a 3500 psi X 33 gpm pump. The difference in extension and retract time is less than ½ second and a 4.29 second cycle time.

A 3" rod changes it to 3.42 second cycle time with all the change on the return (rod) side of coarse. With a difference of 1.34 seconds between exertion and retract. A difference of .87 seconds between a 1.75" and 3" rod diameter.

I wonder if it would be chasing expensive fractions of a second for not much gain in processing time in the big picture, the little bit of gain in cycle time is irrelevant if you are advancing the log and starting the next cut while it is returning as long as the splitter is retracted in time to finish the next cut.



Hi @Hilltop366 , just checked out the site. That's truly useful. As you said fractions of second are irrelevant (especially to me). It's more for the sake of curiosity!

Quote from: jmur1 on May 24, 2020, 07:05:57 AM
Hi Demetrio:
I think the return stroke will be abit faster as you have calculated but dont forget you have to evacuate the opposite oil in the cylinder through your control valve as well.  This means the pump has to push that volume out of the cylinder through the control circuit and back to tank.  In my experience ths will fall somewhere in between the two calculated values.  Ill have to run some tests on my machine to back up my thoughts.  I previously had a 5" diameter cylinder that i had specially modifyied larger ram that did improve cycle time but was really noticeable after i added a piloted return line to tank.  I am now running a 4" that has a standard ram and the return is similar to the out stroke.
Jmur1
@Jmur1 I just noticed that I made a mistake in the calculations I posted. Formulas are correct but I put the wrong numbers when calculating the retraction stroke. Cyl_vol_retraction is 3.2 liters and then the retraction time is equal to 2.3 s. Cycle time is now almost 6s. My mistake :-\. Just in case I checked the math with the calculator suggested by @Hilltop366 and numbers are the same.

Demetrio



Gearbox

You will need to enclose the cylinder so when it is extended no wood can fall behind the push plate . The new splitter for mine will be at 7 seconds full cycle  2.3 on retract no way with all that's going on will I be able to react in time to keep from ripping fittings and hoses .
A bunch of chainsaws a BT6870 processer , TC 5 International track skidder and not near enough time

Demetrio

Quote from: Gearbox on May 24, 2020, 08:38:50 PM
You will need to enclose the cylinder so when it is extended no wood can fall behind the push plate . The new splitter for mine will be at 7 seconds full cycle  2.3 on retract no way with all that's going on will I be able to react in time to keep from ripping fittings and hoses .
Hi @Gearbox , yeah I need to consider that. I think that the best solution would be as in the following YT video: Hakki Pilke Falcon 35 - Efficient firewood processor with low maintenance - YouTube , where the cylinder is embedded into a steel casing with no possibility for the logs to fall behind the push plate and cause damage. Anyway a 7s cycle seems pretty reasonable.
Demetrio

hedgerow

I think building a purpose build splitting chamber like the one in the video you posted makes since. Making sure the log pieces center in the chamber is big. I would use a over size rod cylinder to build your processor. It really speeds up the splitter. They cost more up front but its worth it. I got lucky and found a surplus new cylinder that had a over sized rod in it when I built mine. 

Demetrio

Quote from: hedgerow on May 26, 2020, 12:44:58 PM
I think building a purpose build splitting chamber like the one in the video you posted makes since. Making sure the log pieces center in the chamber is big. I would use a over size rod cylinder to build your processor. It really speeds up the splitter. They cost more up front but its worth it. I got lucky and found a surplus new cylinder that had a over sized rod in it when I built mine.
Hi @hedgerow , I'll throw a look around to see if I can be as lucky as you and find a surplus/second hand cylinder. I had a quote for a new one (anterior flange, 100mm bore, 600mm stroke, 60mm rod, 1/2 inch ports) and it would cost something around 400$.

wiam

That's not a bad price. I would look for 3/4 ports for better flow. Surplus cylinders can be a crap shoot. I got one that was "new/old stock. Split less than 5 cord and seals went. Now I have more than your new price....

jmur1

Hi Demetrio:

The video above made me think of another feature that I have on mine that can cut some serious waiting time.  I have made my knife (splitter) block distance from the hydraulic ram plate adjustable.  This means when I am cutting 12 inch I make the drop bay 14" in length and when I cut 16" I make the drop bay 18" in length and so on.  This means the time for the 24" cylinder is not always running a significant longer time to get the logs to the splitter.  Now depending on your setup that may not matter but for mine it works quite well.

It looks like you are in the starting phase still so make sure you take the time to consider all possible options available.
Also make sure your infeed is wide enough to accept crooked logs.  Make any live rollers nice and wide.  (recommend 2 feet width (600mm))  
For my tank I was running low on oil for a long time no realizing the heat and the air bubbles.  The tank return line should dip into the oil so you reduce splashing and air bubbles, with enough air space at the top to allow for flow/volume changes.  If you plan to use a homemade tank do your research on that and pre install a thermometer and level guage -I learned that one the expensive way!

I detailed my design with a some notes in this forum.  You can see it on the thread:

https://forestryforum.com/board/index.php?topic=97365.0


jmur1

Easy does it

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