need help with feed rate

jpad_mi · July 22, 2005, 10:41:04 PM

I am slowly finishing up the addition on my house and will finally have some time to start working on the bandmill again (only put in 2 days since Labor Day last year). I'm contemplating hydraulic carriage feed, and I don't how fast to make it. Can you guys give me a target feed rate range to shoot for when designing it? The mill has a 16hp gas engine.

Thanks in advance.

ladylake · July 23, 2005, 04:25:09 AM

Jeff You'll need to make it variable. slow down for the big stuff, faster for small stuff and edging. Hydraulic is a real good choice. Just get a flow control valve. Steve

Brad_S. · July 23, 2005, 07:03:47 AM

As ladylake mentioned, it needs to be variable. You'll need to listen to the engine and adjust accordingly. I speed up my feed rate until the engine starts to work hard. As the blade dulls, you'll be slowing down the feed rate. Again, the engine will tell you that.
There is no magic number to shoot for.

BBTom · July 23, 2005, 07:27:29 AM

Jpad, I think I have used a feed rate as slow as 20 fpm and as fast as 150 fpm. It all depends on what you are cutting and the sharpness of the blade. Jog-back on my super is around 210 fpm.

jpad_mi · July 23, 2005, 10:27:17 AM

Thanks guys. Good advice as always. I'll figure for 150-200 fpm at full flow and make sure that the flow control valve I get has good response at low flow, to get me down to 20fpm.

A couple more questions...
I figure a cable wrapped 3 or 4 times around a driven drum and tensioned will give enough friction to drive the head, yet still be able to slip if the carriage runs up against something. Has anybody tried this? How do the commercial mills apply hydraulic power to the carriage drive?

D._Frederick · July 23, 2005, 10:48:25 AM

For 16 hp a feed rate of 20 to 60 ft per min while sawing should cover it. The gig back could be faster.

I use a 3 /16 diameter cable with 3 wraps on a 4 inch diameter capstant will give you plenty of driving force.

ladylake · July 23, 2005, 11:15:31 AM

JEFF I have a B20 Timberking which uses 2 roller chains and a gear drive driven by a hyd motor with a short chain driving the shaft with the drive gears on it. Speed is from barely moving to real fast when returning the head. I think they have a pressure relief valve in case you run into something. Steve

AtLast · July 23, 2005, 03:49:34 PM

Ladylake is right on......make it variable...there are many differant " reostats" if you will... that allow you to make your speed rate adjustable....keep in mind that every species of log cuts differently....on top of that every log cuts differently.....being able to adjust acordingly is critical in my opinion....

Brucer · July 24, 2005, 01:59:04 AM

Quote from: jpad_mi on July 23, 2005, 10:27:17 AM
I figure a cable wrapped 3 or 4 times around a driven drum and tensioned will give enough friction to drive the head, yet still be able to slip if the carriage runs up against something.

Jeff, the capstan drive you're suggesting generally doesn't slip when you hit an obstruction. Capstans increase their grip as the load increases. Use a pressure relief valve in the drive circuit as Steve suggests.

My 28 HP Wood-Mizer is rated at 0 - 125 feet/min forward and 145 FPM return. I have never cranked it up to full cutting speed, even on 6" diameter matchsticks. WIth a 16 HP engine, I would keep your top speed down (say to around 80 FPM) and aim for a lower bottom end speed. When you get into harder, larger diameter logs, you'll want the slower speed.

Buzz-sawyer · July 24, 2005, 02:20:30 AM

Brucer
Do you cut 24" diameter logs at 1 foot a second or faster?

jpad_mi · July 24, 2005, 08:58:28 AM

Thanks again guys!

Brucer · July 24, 2005, 10:21:35 PM

Quote from: Buzz-sawyer on July 24, 2005, 02:20:30 AM
Brucer
Do you cut 24" diameter logs at 1 foot a second or faster?

Nope.

Buzz-sawyer · July 24, 2005, 11:28:47 PM

Brucer said"My 28 HP Wood-Mizer is rated at 0 - 125 feet/min forward"
I can cut a foot a second or so with my 100+ hp saw.....
I have seen a couple of the bigger diesel bands approaching that........but the 16-18 hp dont look to come close..correct?

Brucer · July 26, 2005, 01:27:42 AM

Quote from: Buzz-sawyer on July 24, 2005, 11:28:47 PM
I can cut a foot a second or so with my 100+ hp saw.....
I have seen a couple of the bigger diesel bands approaching that........but the 16-18 hp dont look to come close..correct?

That's what I figure. With a reversing hydraulic motor, there'll be a compromise between a good gig-back speed and what you can reasonably expect a 16 HP motor to do in the cut.

When I was running Louis' 24 HP hyrdraulic Wood-Mizer last year I cut a lot of 24" standing dead Douglas-Fir. Couldn't get close to 60 FPM -- the saw would just bog down. When I hit a flared end on the opening face I'd be down to a crawl (and socking water to the blade to keep it from melting :D)

I was at a Wood-Mizer demo last fall and watched a 42 HP diesel LT-70 slicing up a 30" western white pine log at a pretty good clip. My notes say he was making about 3 passes a minute once the cant was squared up. That was with a remote operator station and accuset computer -- and board return, and a helper.

jpad_mi · July 30, 2005, 12:52:10 PM

I just ordered a flow control valve, hoses, and fittings for the hydraulic feed. I already had the spool valve, motor and a suitable pulley. If I figured everything out right, I should be able to get a max feed rate around 100fpm for gig-back. I'll have about 1 1/4turns of the flow control knob to take me from 0 to 60fpm, so I think I'll be able to dial her in OK for sawing. Thanks for all the input.

jpad_mi · August 14, 2005, 08:28:39 AM

My brother and I installed the hydraulic motor/pulley and flow control valve for the carriage feed yesterday. Didn't have the cable and idler sheaves to finish the install though.

The flow control valve worked great; we could dial the speed right down to nothing, and it has a good range of adjustment. The flow control valve passes full flow in reverse, so gig back will be at full speed regardless of the setting on knob.

Buzz-sawyer · August 14, 2005, 12:27:23 PM

Looking good!
I drive my drum with a sprocket and chain off my hydr. motor....that way I can pull the small splined sprocket of in 1/2 second and move my carriage by hand if needed...

I looked back today at all your pics and looked at your progress in one session........you have done a very nice, and interesting job of posting, and building! 8) 8) 8) 8) 8) 8) 8)

jpad_mi · August 14, 2005, 03:14:19 PM

Thanks Buzz.

Excellent point about using an intermediate chain drive to allow quick disconnect. I'll add it to my list of lessons learned.

Number one on my list is - I should have just purchased a mill and started sawing! If I only knew up front how much it costs to build one, and how long it takes...

Buzz-sawyer · August 14, 2005, 03:43:55 PM

Yea........BUT have you enjoyed building it.or take pride in the accomplishment???

jpad_mi · August 14, 2005, 08:17:45 PM

Yes Buzz, I have enjoyed building the mill and take pride in it. I'm just really anxious to make some sawdust! I've wanted to turn logs into lumber since I was a kid. It's exciting to think that it will (should?) happen this fall.

My hats off to everyone who has built an operational homebrew mill. Seeing the pictures and reading about others projects here on the FF has kept me motivated and provided tons of useful information.