Anybody have a LT40 and a hand tach?

mmartone · November 26, 2013, 08:12:50 PM

I would love to know what the shaft speed is on someones LT40 band wheel shaft.

rmack · November 27, 2013, 08:38:42 AM

that's an interesting question. I tried to determine what rpm my diesel was running at, but it is so well guarded that there isn't really any place I can stick a piece of reflective tape and still read it with my tach.

On the other hand, if I read from the drive side bandwheel, I could still get relative rpm readings for comparison. I will try to get that info today.

Bibbyman · November 27, 2013, 08:57:23 AM

I've used an inexpensive vibration meter to check the RPM setting on the B&S and Onan engines.

Each engine would have its own max RPM setting. That setting should be published in your user's manual. You can call Wood-Mizer and get the correct recommend top end RPM for your engine.

Keeping the engine tuned up and top RPM to spec makes a big difference in the performance of the engine. A couple of hundred drop in RPM results in a dramatic drop in horsepower and torque.

Oops! I answered too soon. I read your post at wanting engine speed.

Years ago someone posted on adding a bicycle RPM meter on the wheel. A couple of others also made the mod. I bought the bicycle meter parts but never got around to putting it on. It would be great to know if the blade is loosing speed under load. It would indicate that the main belt is slipping or you're pushing too fast.

mmartone · November 27, 2013, 09:46:33 AM

I think the back end of the shaft on my idler wheel is open, I could stick the little contact cone on my tach on it and read speed.

ronwood · November 27, 2013, 09:48:20 AM

Bibbyman,

I am wondering if the resolution of the output of the bicycle meter is fine enough to determine that the belt is slipping.

Ron

rmack · November 27, 2013, 10:20:07 AM

QuoteYears ago someone posted on adding a bicycle RPM meter on the wheel. A couple of others also made the mod. I bought the bicycle meter parts but never got around to putting it on. It would be great to know if the blade is loosing speed under load. It would indicate that the main belt is slipping or you're pushing too fast.

QuoteI think the back end of the shaft on my idler wheel is open, I could stick the little contact cone on my tach on it and read speed.

I think a digital hand held tach is fairly accurate, to within 1 rpm, not only could you check the main belts for slippage, you could compare drive side bandwheel with idler side under load. 8)

Bibbyman · November 27, 2013, 10:25:12 AM

Quote from: ronwood on November 27, 2013, 09:48:20 AM
Bibbyman,

I am wondering if the resolution of the output of the bicycle meter is fine enough to determine that the belt is slipping.

Ron

Maybe someone who has added the bicycle tachometer will see this post and clue us in.

DR Buck · November 27, 2013, 11:02:48 AM

Back early in the "useful sawmill mods" thread is a post by VA Sawyer about adding a tach to the LT 40. I put one on mine way back then and it works great. I can monitor rpm while cutting and maximize cutting speed. When engine rpm starts dropping I slow down feed rate.

Magicman · November 27, 2013, 11:13:19 AM

I have an accurate handheld that I use to adjust my engine's rpm. The crankshaft end is open, so it is easily done.

It will be Monday at the earliest before I can read the rpm of the bandwheel.

mmartone · November 27, 2013, 04:37:59 PM

I just ran mine to see where it was. The engine was WOT 4800 with a shaft speed of 1570 (3:1 ratio), all the newer ones make max hp at 3600. I never run the engine up to that sort of speed while cutting and only use WOT when its slowing in a big sappy pine log. The idle side bearing at that speed was slinging grease out of it, first time I ever saw that!

Dave Shepard · November 27, 2013, 04:49:29 PM

What engine do you have? 4800 sounds way too high. The small V Twin engines I've run are usually 3600, although the Kohler that I'm putting on an LT40 is set to run at 3400.

mmartone · November 27, 2013, 05:55:37 PM

Yes its to high.. but the engine did it when I set it to WOT with the blade engaged. :-\

Chuck White · November 27, 2013, 06:57:54 PM

Quote from: mmartone on November 27, 2013, 05:55:37 PM
Yes its to high.. but the engine did it when I set it to WOT with the blade engaged. :-\

What is WOT?

Does that mean Wide Open Throttle?

Most of the gasoline sawmill engines run max rpm at 3,600 and low rpm at 1,800.

When I'm sawing (actually in the wood) an average size White Pine, my tach reads around 3,200 to 3,400 rpm!

mmartone · November 27, 2013, 09:44:34 PM

Yes, wide open throttle. Thats why I'd like to know what a regular non custom woodmizer LT40 wheel shaft speed is.

pineywoods · November 28, 2013, 09:59:01 AM

Quote from: Bibbyman on November 27, 2013, 10:25:12 AM
Quote from: ronwood on November 27, 2013, 09:48:20 AM
Bibbyman,

I am wondering if the resolution of the output of the bicycle meter is fine enough to determine that the belt is slipping.

Ron

Maybe someone who has added the bicycle tachometer will see this post and clue us in.

Bicycle speedo works well, and it's cheap. Readout in mph+tenths (or kph if you like metric). Or resetable distance traveled, which will equate to blade through the wood. configureable for different bandwheel sizes.Runs off a button battery, which won't last but a few days of sawing. The pickup is a small magnet attached to a bandwheel and a pickup coil mounted somewhere where the magnet passes within 1/4 inch. I recommend mounting on the idler bandwheel. Plenty sensitive enough to see a slipping drive belt or blade getting dull. I just about quit using mine, the battery died, and never got around to replacing it. Easy to calculate bandwheel/engine rpm using the wheel and pulley diameters.

mmartone · November 28, 2013, 10:01:59 AM

Yes as long as there no slipping, that TinyTach I bought is pretty cool, its also an hour meter. First saw one on a friends Prodrive on his duck boat.

rmack · November 29, 2013, 01:14:28 PM

I got all set up to check mine yesterday, only to find out the batteries were dead in the tach, today is gloomy with freezing rain coming down... think maybe I'll take a hibernation day.

mmartone · November 29, 2013, 09:53:59 PM

I keep a spare set of batterys in my tach case because I have had that happen!

rmack · November 30, 2013, 04:08:57 PM

1168 rpm at the drive side band wheel.

mill is in my sig.

mmartone · November 30, 2013, 08:04:17 PM

Thats fantastic, thank you for that valuable info! I opened a pine log today keeping my rpms below 3600, saw ran great. Since my ratio is 3.05 (4800/1570) that sets my wheels at about 1180 which is right on the money, pretty lucky since I got that engine pulley from a friend of mine and adjusted it on the lathe. Thanks again.

rmack · November 30, 2013, 08:08:39 PM

Quote from: mmartone on November 30, 2013, 08:04:17 PM
Thats fantastic, thank you for that valuable info! I opened a pine log today keeping my rpms below 3600, saw ran great. Since my ratio is 3.05 (4800/1570) that sets my wheels at about 1180 which is right on the money, pretty lucky since I got that engine pulley from a friend of mine and adjusted it on the lathe. Thanks again.

I believe my blades are 158", that would put cutting speed at 15378.66 surface feet per minute, compare that to mild steel @ 90 surface feet per minute.

that blade's going almost 180 mph :D

Nomad · December 01, 2013, 07:32:30 AM

Rmack, I think you used gubermint math. :D Plug in 59.69 (wheel circumference) instead of 158.

petefrom bearswamp · December 01, 2013, 08:12:42 AM

Maybe a dumb question.
Should wheel measurement be taken at the outside or at the point in the groove where the v belt sits at its lowest?
pete

rmack · December 01, 2013, 08:50:18 AM

Quote from: nomad on December 01, 2013, 07:32:30 AM
Rmack, I think you used gubermint math. :D Plug in 59.69 (wheel circumference) instead of 158.

lol! I guess cipherin' aint my strong suit. ;D

rejigged it comes out to 5840 sfpm, or just over 60 mph

I just rounded it up to 60 inches diameter, though it is probably a bit more at the outside of the belt.

Dave Shepard · December 01, 2013, 10:34:44 AM

Quote from: petefrom bearswamp on December 01, 2013, 08:12:42 AM
Maybe a dumb question.
Should wheel measurement be taken at the outside or at the point in the groove where the v belt sits at its lowest?
pete

I think if you measure the diameter at the same location on both the drive and the driven sheaves, you should be fine. I would measure them at their largest diameter.