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BandSaw Mill Engine Query

Started by Koopsy, January 11, 2022, 01:56:02 PM

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Koopsy

Hello everyone,

Currently, I have a 4 cylinder 1987 Ford Tempo engine running in my mill. It's on the way out and I'm looking for a new engine. 
Thinking about a Yanmar or a Perkins diesel. 
Not sure if a horizontal or vertical engine would be better?
My biggest issue is I don't know what size engine I need? My Ford Tempo had enough power to cut through some big wood, and I want something that has that kind of power. 

Any ideas on what make and model would work?
I'd rather have more power than not enough. 

Nebraska

What size is your mill? What type of product are you typically  milling?  A picture of your set up would help folks advise you.

rusticretreater

So is this a homemade mill or something you modified?

This may be a bit technical, but I would look at the current engines horsepower and torque curves.  This will give you an idea of what you are looking for in your next engine.  More torque at a lower rpm is better as over speeding a blade is not good.  You may also be able to get your rpms and torque into a range you are comfortable with.  A new clutch might also be required.

At any rate, you will be able to determine if an available engine is suitable for your needs.
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biggkidd

More information will help these guys get you the correct answer. What kind of mill is the first thing that comes to mind. I'm betting a circular mill not a band mill. Is the engine stationary or does it ride a track? Is size space weight a concern?  Lots of questions to come up with a correct answer.
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Koopsy


Koopsy

The deck is 22' but can be extended to 44'. 
The biggest we cut is 36" at the butt.

Ianab

For reference that's a 2.3l engine, rated for 90hp. But I'm guessing it's not being run at max revs? So more like 40-50 hp ~3,000 rpm maybe.  That's still plenty of power for that size of mill. 

A 30-40 hp industrial diesel will make that power at it's regular ~3,000 rpm, and have a heap more torque which helps with milling. 

Also, look at commercial mills and see what engines they spec at a similar size. An LT40 for example has the option of a 35hp diesel , for "more power". So I'd  be looking in that sort of range.  Engine will likely weigh less than the existing one, but the mill looks solid and isn't portable, so weight likely isn't a big deal. 

Weekend warrior, Peterson JP test pilot, Dolmar 7900 and Stihl MS310 saws and  the usual collection of power tools :)

Koopsy

Alright, thanks.
Would you happen to know if a vertical or horizontal engine would be better for a mill?
I'm looking at the Yanmar TS300, which is a single horizontal piston(1.5L) diesel that makes 30HP @ 2400RPM vs the Yanmar 3TNV86CHT 3 cylinder vertical piston diesel(1.6L) that makes 34HP @ 2600RPM.

I'm just testing the waters, I'm open to better alternatives. 

Ljohnsaw

I would thing the 3 cylinder would have more torque then the single cylinder.
John Sawicky

Just North-East of Sacramento...

SkyTrak 9038, Ford 545D FEL, Davis Little Monster backhoe, Case 16+4 Trencher, Home Built 42" capacity/36" cut Bandmill up to 54' long - using it all to build a timber frame cabin.

rusticretreater

Don't get too fixated on horsepower.  Looking at the charts below, you will see that both engines have nearly identical horsepower curves.  But the lower chart, the Yanmar 3TNV86CHT has a much higher torque output and is consistent throughout the rpm range.  1 kg = 9.80665 N.  The TF300 does not put out as much torque and falls off in the upper rpm range.  

Therefore, if the 3TNV86 engine bogs slightly it will still have significant power to pull the blade through the log where the TF300 will struggle.  Think of torque as twisting power.  It seems counter intuitive that an engine would have less twisting power as it runs faster, but that is the physics of engines.

Always look for the flat, wide torque band in engines or the highest torque in the required rpm range.

torque approx: 96 - 105.9


 


3TNV86CT
27.4~32.4/2,500~3,000
124~127/1,625~1,950


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Ianab

The advantage of diesel in a sawmill application is that torque. You can see from the graphs that from the normal operating rpm, if the mill begins to bog down, the torque actually increases. This resists further slowdown, until you get into a real overload.  A Gas engine usually has a torque curve that drops off quicker as the revs drop (in the range we a working anyway). So if you fully load the gas engine, start losing revs, torque drops off, and you continue to bog down even worse. And that's the limiting factor on the mill, once you load the engine to 100%. and start loosing band speed, that's when you have problems. 

Effectively a 30hp diesel can perform with a 40+ hp gas engine on a sawmill. 

I'd expect the 3 pot engine to be a lot smoother running? Less vibration generally means less problems? I don't think the cylinder orientation makes a big difference, that's usually about fitting the engine in a certain space. 
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PoginyHill

HP = Torque X RPM.

Diesels normally run a lower RPM. But, as noted by @rusticretreater , their torque curve is rather flat compared to a gas engine. Gas engines generate their higher HP with RPM, not torque.

But power is power. Higher RPM can be turned into more torque (at a lower rpm) with gear reduction.
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jpassardi

Quote from: PoginyHill on January 12, 2022, 08:04:38 AM
HP = Torque X RPM.

Diesels normally run a lower RPM. But, as noted by @rusticretreater , their torque curve is rather flat compared to a gas engine. Gas engines generate their higher HP with RPM, not torque.

But power is power. Higher RPM can be turned into more torque (at a lower rpm) with gear reduction.
To clarify: HP=Torque x RPM/5252  -  This is why every engines torque and horsepower curves will always cross (be equal) at 5252. As we all know: most diesels don't produce efficient power that high.
True: power is power
Horsepower is basically how much torque can be made in a given time. Torque is static, horsepower is dynamic which translates to acceleration. This is why horsepower is king in racing:  acceleration.
A Tugboat or Sawmill's performance needs steady work, not acceleration. If it can be done at a lower RPM, the result is longevity and efficiency. This is where a diesel's lower rpm power curve will shine.
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Gearbox

do you know what RPM the engine is turning now .Once you know that you have some numbers to work with . There are some 2300cc engines in use in the construction industry they were bullet proof  
A bunch of chainsaws a BT6870 processer , TC 5 International track skidder and not near enough time

tacks Y

If the Ford is not good why not try a Chevy?

47sawdust

Koopsy,
What's the fan for? Doesn't look like it will be overheating in the picture?
Mick
1997 WM Lt30 1999 WM twin blade edger Kubota L3750 Tajfun winchGood Health Work is my hobby.

fluidpowerpro

Also, I have always been of the understanding that you want to look at the torque curve and try to run at an RPM where if the engine slows down while working, you run "back up" the torque curve. If you end up going over the peak, the torque drops quickly and the engine kills.

For example, on the curve below I would say 1800 - 2000 RPM is optimal. As the engine loads, it is increasing torque output down to about 1650 RPM. Below 1650 the torque starts falling. At this point, unless the load on the engine is reduced, it will kill.

Change is hard....
Especially when a jar full of it falls off the top shelf and hits your head!

Koopsy

Alright, thanks everyone for your input.

The fan is used to help cool the engine and helps blow off all the sawdust as you're making a pass. The ol' engine ain't what it use to be. It's held together with duck tape, bubble gum, and sheer will power.

All the information about torque curves is helpful. 
I'm uncertain of the cutting RPM of the current Ford Tempo. We've been running it for so long by feel alone. The engine weight carries so much inertia it pushes right through the log once you get it going. 

Would it be best to have an engine that peaks torque at 1600 or 2500RPM?


fluidpowerpro

I would lean towards the lower RPM of a deisel and the change your pulley size to achieve the optimal blade speed.
Change is hard....
Especially when a jar full of it falls off the top shelf and hits your head!

fluidpowerpro

Or another way to say it is that regardless of what engine you choose, you can change pulley sizes to get the optimal blade speed. If you find the saw cuts good now, then adjust pulley size so the drive wheel RPM stays close to the same as now.
Change is hard....
Especially when a jar full of it falls off the top shelf and hits your head!

Ianab

Might be a good time to sit down and do some maths about blade speed, engine RPM, and work out pulley sizes to get the optimum ratio. What you have now is obviously in the right ballpark as it's working well enough, and it's a fairly large engine for a bandsaw, hence the inertia of the flywheel helping in any tough spots. But if you are reworking things, might as well optimise the pulleys for the best results.
Weekend warrior, Peterson JP test pilot, Dolmar 7900 and Stihl MS310 saws and  the usual collection of power tools :)

jpassardi

Ianab is spot on here - Blade speed is key.

I would first decide if you want to go gas or diesel. From there modify (if needed) your pulley sizes to run about 5000 FPM blade speed - Not RPM-Blade Speed.
A small gas engine will have a design speed of 3600, a diesel will be lower.
I would run 5/8 pulleys and a BX belt to carry the horsepower without slipping.

It looks like your driven pulley may be too small in the photo especially once you don't have the xtra power and flywheel inertia that you do now. If you decide on a diesel it may be pretty close as is.

For example: a 5.25" drive and 19" driven pulley combo will put you about 5000 FPM with a 3600 RPM gas engine. This assumes you have the blade on 19" pulleys.
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Koopsy

Awesome, thanks again everyone.

Bobby


Koopsy

Here's the engine I've recently purchased for the mill. 

Laidong 1.5L 3 Cylinder Diesel.
23HP @ 1800 RPM.


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