Back at the homemade sawmill video added

JRWoodchuck · February 18, 2018, 12:09:40 PM

You'll want to get the H Bushing style pulleys they are much stouter and hold up better(learned the hard way on that) and then just get 1 1/2" on everything. I built my mill with a lot of surplus center parts I don't have any cross support on my mill. I have used B56 and 57's right now I am on 56's don't really notice a difference between them. Look up changing the blade on a Linn Lumber mill and you'll see how they adjust the mill like the picture you posted.

Kbeitz · February 18, 2018, 12:24:19 PM

Yes the Bushing style pulleys let you different size shafting.

Georgia088 · February 18, 2018, 12:45:08 PM

Thanks ya'll.

For some reason I didn't get several replies before I posted this. I'm not sure why but I apologize if it reads out of place.

So, since I'm going to completely do away with golf cart rear end; my plan is to keep the centrifugal clutch from the golf cart and run a belt from it to a drive pulley that is on the same 1-7/16" shaft that my sawblade pulley is on. Any idea on what size the drive pulley will need to be? I'm using a 13 hp harbor freight predator engine. Turns 3400 rpms I think.

Thanks

gww · February 18, 2018, 02:02:24 PM

Georgia.....
If you know the size of your what your blade rides on and your motor pully, you could play around with this to find out what you want. My guess is as low as 3500 fpm to 4500 fpm would be the goal. Here is the caculator.Bandspeed Calculator
Good luck
gww

Georgia088 · February 19, 2018, 07:22:19 AM

So, if I'm understanding this right; my centrifugal clutchis 6" o.d. My motor is 13 hp with 3600 rpm. This would mean I would need a 24" diameter driven wheel to get my fpm below 4500?! Yikes! I can't do that!
Is reducing my drive pulley my best option? I would then have to create a manual clutch mechanism.
Thanks!

Kbeitz · February 19, 2018, 07:29:48 AM

Quote from: Georgia088 on February 19, 2018, 07:22:19 AMIs reducing my drive pulley my best option?

You could put a jack shaft in...

Georgia088 · February 19, 2018, 08:51:12 AM

Hmmm ok that's a good idea. Although I'm still a little confused about all this calculation. My motor is listed at 3600 max rpm. 2500 is when it is at its highest rated torque according to specs. My problem is I need to reduce the fpm so, by reducing rpms of motor and getting its max torque shouldn't I be using the calculator at 2500 rpm and plan on running it at that speed? This would allow me to use a smaller driven pulley and I would be getting the max torque.
Thanks!

gww · February 19, 2018, 11:10:27 AM

Quote from: Georgia088 on February 19, 2018, 07:22:19 AMo, if I'm understanding this right; my centrifugal clutchis 6" o.d. My motor is 13 hp with 3600 rpm. This would mean I would need a 24" diameter driven wheel to get my fpm below 4500?! Yikes! I can't do that!
Is reducing my drive pulley my best option? I would then have to create a manual clutch mechanism.

It seems like you are missing a pully. You should have a drive from motor (6 inch) a pully behind the wheel on your shaft, and then the pullys or tires your blade rides on. Any one of them could be changed. I ran mine a long time with a jack shaft and it helped me at the time but I am glad that I am more direct drive now. I did reduce my motor pully size. I do not think you will be happy cutting the motor rpms down and you should use the 3600 rpm in the caculation. Jack shaft may be the cheapest route to go but if you are still running tires, a bigger tire and differrent blade size might be easiest. I do think you need to get your blade speed down. Even 5000 fpm might be ok and you could play a little with the engine rpm then but I would want it close to running full bore.
Good luck
gww

coach08 · February 19, 2018, 11:37:34 AM

talking with customer support at briggs and stratton. They say after 2500 rpm I would not gain any torque only speed. They also said that engine would not run hot at slower rpms. And although I agree with GWW. I thought the faster the better but maybe Ive always been wrong. (which wouldn't be too suprising). Saying this to ask Georgia088's question again. Why not run the engine at lower (2500) rpm with max torque?

Den-Den · February 19, 2018, 11:59:36 AM

Quote from: coach08 on February 19, 2018, 11:37:34 AM
talking with customer support at briggs and stratton. They say after 2500 rpm I would not gain any torque only speed. They also said that engine would not run hot at slower rpms. And although I agree with GWW. I thought the faster the better but maybe Ive always been wrong. (which wouldn't be too suprising). Saying this to ask Georgia088's question again. Why not run the engine at lower (2500) rpm with max torque?

Max torque at the engine is 2500 rpm. Max power would be at full throttle. With correct pulley ratio, you run full throttle to get the full power of the engine. A jack shaft would allow you to use the clutch and adjust your band speed with the pulley ratio.

Kbeitz · February 19, 2018, 12:09:54 PM

Quote from: coach08 on February 19, 2018, 11:37:34 AMThey also said that engine would not run hot at slower rpms.

They are so wrong. The newer engine are made to keep cool at top speeds. They are air cooled. Low speed higher temps. Running at full throttle increases the speed of the cooling fan, meaning that more cool air is being pushed over the engine, causing the operating temperature to drop. Google it...

coach08 · February 19, 2018, 12:16:13 PM

Not arquing the point..... just saying what they told me. I think I remember reading your post that said you ran your engine at 3200rpm. Was that your wot or older engine. So your saying I should run at WOT or what rpm? Still trying to get fpm good. Guess going to have to change pulleys.

Kbeitz · February 19, 2018, 12:24:17 PM

I would run at WOT. A load on you machine will drop your RPM some anyway.
The old cast iron engines could be run at low RPMs but the newer stuff needs run at top speed to keep the heat from hurting it.

Kwill · February 19, 2018, 02:07:59 PM

So you guys are saying to base your pulley sizes on max rpm? I was figuring mine of half throttle which figured out to be a 10.25 inch pulley and a 4 inch drive pulley and 21 diameter which put mine at 3800 sfpm. Wide open would put it over 7000. So should I go bigger on the driven pulley?

gww · February 19, 2018, 03:22:00 PM

Kwill
use the caculator to find out but I would say you need to go smaller on your engine pully.
Cheers
gww

Kbeitz · February 19, 2018, 03:28:18 PM

Quote from: Kwill on February 19, 2018, 02:07:59 PMdriven pulley

On the driven pulley bigger is faster smaller is slower.

coach08 · February 19, 2018, 04:06:20 PM

according to the bandspeed calculator a bigger driven pulley makes the surface feet per minute slower

Ljohnsaw · February 19, 2018, 04:15:30 PM

Quote from: coach08 on February 19, 2018, 04:06:20 PMaccording to the bandspeed calculator a bigger driven pulley makes the surface feet per minute slower

Yes, the driving wheel getting bigger makes it go faster, but the driven wheel being bigger goes slower.

Georgia088 · February 19, 2018, 04:37:09 PM

Ok, so next question. I said my centrifugal clutch that came off of the golf cart was a 6" and it is. However that's with a 1-1/4" belt. I put a 1/2" belt in it and engaged it. When it is engaged, it is running around a diameter of about 3-4" inside that clutch. This would be great if I could do this because I could use about a 12" pulley as the driven wheel and use my current clutch... will this work?

Kwill · February 19, 2018, 04:52:19 PM

Looks like with the engine I'm using 13 HP predator the best options would be 3 inch engine pulley and 12 inch shaft pulley. @ 3400rpm it is 4600 sfpm

Georgia088 · February 19, 2018, 04:59:28 PM

We are using the same engine and I am thinking the same thing. We are thinking of getting a 12.75 diameter pulley from surplus and trying the current centrifugal clutch I have from golf cart. Although, it's od is 6" with a 1/2" belt the belt engages and rides at about where it is 3-4" diameter. I'm not sure how this will work. I would love yalls feedback. I guess if it doesn't I will but he 3" centrifugal clutch from surplus center... I don't really want to though.

starmac · February 19, 2018, 05:20:59 PM

Sounds like your clutch is similar to a snow mobile clutch, I do not know, but I would almost bet you are going to run into problems running one small belt.

gww · February 19, 2018, 05:33:54 PM

Kwill
Sounds good, maybe a little fast but close enough to play with rpm if needed. I like it.

Georgia...
I do not know how clutches are made. I am guessing it does not have a shaft to put a smaller pully on it. Is the front of the pully open or does it have a bar in front of it. I would weld a pully to the 6inch pully if there is a way to set the small one up against the big one. I don't even know if that is possible but is something I would be looking at cause that is how my mind works.
Cheers
gww

Kbeitz · February 19, 2018, 06:12:52 PM

Driving driven ... Yep yep... Got it backwards... Dumb me...

Kbeitz · February 19, 2018, 06:16:58 PM

Isn't you'r centrifugal clutch one that closes up on the belt as the engine speed increases? If it is you might be able to lock in in the smallest belt size so it wont close up to the larger size.