Number of belts vs hp

[Josko Catipovic]

I got a 8" Delta 37-315 jointer with a 3 Hp (Baldor TEFC) motor but only a single 'A' belt to the curtterhead. I wonder whether it should have more than one belt given the 3 HP motor and the 6" and 2 1/4" pulleys. Seller is a boatbuilder who upgraded it to 3hp to take 'hefty' cuts off boat lumber. I found a Baldor manual on power transmission but frankly, got lost in the morass of technical details. Would anyone know what the rule of thumb is in this case? Would I gain anything by two belts? Thanks in advance

[Zachary Hoyt]

If you push it too hard, what happens? Does the belt slip or does the motor stall? This will answer your question, I think.

[Josko Catipovic]

Motor bogs down. Still, I wonder if I'm overstressing things.

[Dan Friedrichs]

It depends on the sheave diameters, but something like a ~3" diameter pair of sheaves should be capable of at least 2HP with an A belt. If the sheaves are larger (~5") you could get 5HP out of a single A belt.

It's primarily a matter of providing enough surface area on the belt to make sure it doesn't slip. Larger sheave = more surface area = more power transmission without slipping.

In your case, since you aren't slipping the belt, that's not the issue. Sounds like you're either:

1) Working the motor too hard (are the knives sharp? Is the table waxed? Are you taking reasonable width/depth cuts?)

2) Something is wrong with the motor or its power supply (does it have a sufficiently-large circuit supplying it? Does the motor have a 'run' capacitor and is it good?)

[David Kumm]

The machine was designed within certain load limits and although well built, is not overbuilt. A larger motor and extra sheaves just allows for more load to the machine and bearings. That machine isn't made to handle a 3 hp motor bogging down so I'd not add belts to allow even more stress. Dave

[Bill Dufour]

Given the work needed to add an extra belt I would not bother. You will have to cut the base open and maybe grind some of the fence off as well. Not sure if the motor mount has enough in and out adjustment or if you will have to machine new mounting slots and weld up the old ones.
maybe switch to a cogged belt to help on the smaller pulley.
Bill D

[Martin Wasner]

If it's not slipping, what's the issue?

I've got ten course shapers that get worked. Just a single belt on them.

[Warren Lake]

Martin

was that a ten course dinner?

or a ten horse shaper. Im planing on putting a chev 350 on one of mine, Maybe an Lt-1, never too many hp.

[glenn bradley]

On my gear, as delivered:
3HP 8" Jointer - 1 Belt
3HP Tablesaw - 1 Poly V-Belt (ribbed, mulit-vee, whatever)
3HP 15" Planer - 1 Belt

[Van Huskey]

or a ten horse shaper. Im planing on putting a chev 350 on one of mine, Maybe an Lt-1, never too many hp.

Might I suggest not stopping at a measly LT1. Get something with some REAL torque with ~1200hp and will run 24-7 for decades outside of maintenance.

Behold the 32 liter CAT C32, you will need to use more than 1 belt and maybe upgrade the spindle bearings...

394939

[Martin Wasner]

Martin

was that a ten course dinner?

or a ten horse shaper. Im planing on putting a chev 350 on one of mine, Maybe an Lt-1, never too many hp.

Yeah yeah yeah. I suck at proof reading and I've got a phone that likes to auto correct things into incoherence.

This isn't anything new.

[Josko Catipovic]

Thank you, all. One belt it is. I was just wondering if it makes sense to get another belt given the motor upgrade. Not planning to abuse this in any way.

[Rod Sheridan]

Might I suggest not stopping at a measly LT1. Get something with some REAL torque with ~1200hp and will run 24-7 for decades outside of maintenance.

Behold the 32 liter CAT C32, you will need to use more than 1 belt and maybe upgrade the spindle bearings...

394939

Funny timing, I'm load testing a Cat 3516 quad turbo 2,000Kw set today.

I think it's 69 litres, V16, makes the C32 look like a pup engine:D

Regards, Rod.

[Ole Anderson]

So now I am wondering why they put triple belts on 3 hp table saws?

[Warren Lake]

geez Van you dont mess around :).

My sister sent me an auto correct thing conversations between kids and their parents, hard to believe they were not doctored but they were funny. Interesting on the belt thing some machines here have three then ones with almost double HP up to 9hp have one. I prefer the Cog belts if that is the right name, Belts on my table saws even from new are stiff and feel crappy if you hand turn something. Belts on the shapers with all the notches cut out, turn like there is barely a belt there.

[John McClanahan]

Josko, If the wiring was not upgraded to match the night motor, that may be why it still bogs down.


John

[Josko Catipovic]

Josko, If the wiring was not upgraded to match the night motor, that may be why it still bogs down.


John

We did bog it down taking off 3/16" of 8" wide black locust. Seller wanted to show me what it could do. The motor slowed down, but the belt did not slip. Wiring seems to be 12ga throughout. Based on this thread, I plan to leave it as is. Still, as Ole noted, why are manufacturers now putting multiple belts on 3 hp machines?

[Warren Lake]

dont know the jointer. An 8" jointer is still in toy land. (some brands exception) To take a very hard wood then take a pass of 3/16" deep on that machine is not to bright. I changed out the motor from the 1 1/2 Hp recmmended when I got a new general 8" jointer eons ago to 2 HP Leeson farm duty. PUt a piece of hard maple 8" wide and take a third as much off and it was still gutless.

[Brian Runau]

Torque rating of a v-belt drive is based on the size of the drive sheave, driven sheave, center distance of the drive and belt being used. Cogged belts transmit more HP than the smooth versions and can be an easy fix, but they have their limit. Send me the info and I would be glad to check for you. Brian

[Josko Catipovic]

So, with 3 HP 1725 rpm motor, 6" pulley at the motor, 2 1/4" pulley at the cutterhead, do I deliver more power to the cutterhead with one A-size belt or two?

[Brian Runau]

So, with 3 HP 1725 rpm motor, 6" pulley at the motor, 2 1/4" pulley at the cutterhead, do I deliver more power to the cutterhead with one A-size belt or two?

What is the center distance between the two shafts of the drive?

Thanks.

Brian

[Josko Catipovic]

20" between shaft centers

[Mike Kees]

I have the exact same jonter and mine came with a 1h.p. baldor motor. I thought it was a bit light and then decided to try for a while. It has worked fine for the last five years.Recently ...upgraded to a 16'' paoloni with a 5.5 h.p. and it is definitely more power. Maybe I just did not know what I was missing.Mike.

[Brian Runau]

20" between shaft centers

Josko, sorry for the delay. I've been looking for my software program, too lazy to do it long hand. torque(ft lbs)=hp x 5252/rpm 3HP MOTOR HAS 9FT lbs of torque. You have a 2.67 ratio speed up drive. So at the driven speed of the 2.25" dia pulley you have a speed of 4672 rpm. Torque at the driven pulley is t=3x5252/4672 net is 3.37 ft lbs of torque. 3ft lbs/hp is the rule so you are delivering @ 1.123 HP at the cutter head.

Let's say you changed the 2.25" pulley to a 6" to make it a 1:1 ratio drive. The A belt could deliver up to 7.42 HP with a single groove set up. Don't know what the original design cutter head sped should be, but I wonder if whoever put he 3HP motor on it changed the driven pulley size to speed up the cutter head.

Thanks.

Brian

[Bruce Wrenn]

So now I am wondering why they put triple belts on 3 hp table saws?When Delta designed the Unisaw back in the thirties, there were only cotton core belts. By using three belts, power transmission was reliable. Today's belts with synthetic cores can handle much greater loads. That's why you have a single serpentine belt to drive all the accessories on your car. PM only uses two belts on the PM 66 which could be had with a 5 HP motor

[Josko Catipovic]

Josko, sorry for the delay. I've been looking for my software program, too lazy to do it long hand. torque(ft lbs)=hp x 5252/rpm 3HP MOTOR HAS 9FT lbs of torque. You have a 2.67 ratio speed up drive. So at the driven speed of the 2.25" dia pulley you have a speed of 4672 rpm. Torque at the driven pulley is t=3x5252/4672 net is 3.37 ft lbs of torque. 3ft lbs/hp is the rule so you are delivering @ 1.123 HP at the cutter head.

Let's say you changed the 2.25" pulley to a 6" to make it a 1:1 ratio drive. The A belt could deliver up to 7.42 HP with a single groove set up. Don't know what the original design cutter head sped should be, but I wonder if whoever put he 3HP motor on it changed the driven pulley size to speed up the cutter head.

Thanks.

Brian

Thanks much Brian,

I'm trying to follow your math but could use a bit of help: if the motor is generating 3 HP but only 1.123 HP is delivered to the cutterhead, where does the rest of the power go? If it's dissipated in the belt, that's almost 1.4 KW of heat generated in the belt, so it would surely melt before long. Does this mean that if i upgrade to two belts, I can deliver 2.246 HP to the cutterhead? Does this number (1.123) have anything to do with the pulley ratio? Thanks in advance.

[Rod Sheridan]

Thanks much Brian,

I'm trying to follow your math but could use a bit of help: if the motor is generating 3 HP but only 1.123 HP is delivered to the cutterhead, where does the rest of the power go? If it's dissipated in the belt, that's almost 1.4 KW of heat generated in the belt, so it would surely melt before long. Does this mean that if i upgrade to two belts, I can deliver 2.246 HP to the cutterhead? Does this number (1.123) have anything to do with the pulley ratio? Thanks in advance.

Hi, your torque is 3.37 pound-feet at 4672 RPM as per the above.

That's 3 HP, not 1.123 HP.

3 pound-feet per HP is an approximation that only works at 1,800 RPM...................Rod.

[Brian Runau]

Rod, thanks let me review on my end. I really did want to do this long hand!

Thanks.

Brian

[Jacob Reverb]

Coming in late and haven't read the whole thread, but thought I'd add that I have a big compressor that's supposedly pulling 5 hp at 3450 rpm on drive sheave through one belt...I'm sure it must be a "B" belt...

@Brian Runau - Are you an ME? I'm getting ready to build a bandsaw mill and was curious whether I could get 22 hp through a single B belt with maybe a 4" drive sheave and 18" driven sheave...I found some tables online but I'll be darned if I can figure out how to read them...times like this I wish I had studied ME as planned, and dad ain't around to ask anymore...

[Brian Runau]

Rod:

yes my thought to convert ft lbs to HP at the higher rpm is incorrect. The match of 3.37ft lbs of torque at the cutter head is correct though. So this drive is delivering @ 1/3 the force in torque that the motor generates.

Thanks.

Brian

[Brian Runau]

Josko:

The belt does not generate HP/torque it only needs to be sized large enough to deliver the hp/torque of the drive(motor, pulleys). HP is a function of speed and torque. The faster the rpm the lower the torque based on the same HP.

3hp motor at 1800 rpm generates 9 ft lbs of torque 3hp motor at @3600 rpm generates 4.5 ft lbs torque

Only way to change the force(torque) at the cutter head would be to increase the HP or change the ratio in the drive so the cutter head speed is slower based on using the 3hp motor. If you go to a 5hp motor the motor shaft is different size and you would might need to redesign the v-belt drive.

Brian

[Josko Catipovic]

My original question is whether I would get any more power to the cutterhead or improved performance by changing from one 'A' belt to two. (FWIW, recommended cutterhead rotation for this jointer is 4700 rpm, and the 6":2.25" pulleys get me close to that.) From the drift of this thread, it souds like as long as the single belt is not slipping, it is adequate for the job, and a second belt would not help. If there's any reason whatsoever to change this drive setup from one belt to two, I'd love to hear about it. (And yes, the machine housing will accomodate a double pulley both at the motor and cutterhead.) Thanks again for all the help.

[Brian Runau]

Josko, I do not believe adding belts will generate any more torque at the cutter head. The single belt is large enough to transit the power that is in the drive.

[Andrew Stern]

Belts have a "practical" limit to what they can carry. Much depends on sheave speeds bit also on contact angles. Slippage promotes glazing and wear and both limit the belts capacity and life. If an A section belt was the original design (and all designs are compromises) then the engineer might have also considered issues such as slippage as a good thing and avoiding motor overloading. Overheating short-lived motors quickly due to low grade insulation in the early days and motors had to be overbuilt to dissipate heat. Early multi-belt systems were problematic due to deferential sheave wear and need for highly matched belts. Today belts are made to a better tolerance and "matching" is easy to accomplish with sequential mold numbering. I would be to reluctant to set up to a multi-sheave system unless motor was "modernized". Bearings are probably fine if you tension properly. Most important to look how and where belt is running in the sheave. If you go with one belt make sure it is a "A" section and not a "4L" which is x-sect dimensional similar but not the same. A belts have a different calculated "length" and that can be confusing when model number contains a length code, but they are better built. An AX belt is cogged which can be a slight improvement in transmitted power. my $0.02