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Armilite

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Like this Belt Drive, the Big Pulley only uses (2) Bearings with a Spacer in between, I would use (3) Bearings.

PPG BELT DRIVE 2.58 - 4.jpg
 

proppastie

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2 points define a line....only 2 of the balls would be in contact at any one time....stick with 2 bearings, or one big roller bearing
 

Aviacs

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Armilite -
My comments were directed to Blane c.
Did you look at his design with a single taper roller bearing, 11+" of shaft, and a radial at the other?
No method to control preload or to maintain clearance.

also read Proppastie's note above.
Multiple bearings don't help if the load alternates among single bearings or ultimately ends stressing only one of a pair.
Matched opposed sets with preload can be used at one end (lathe spindle design, e.g.) and a third somewhat distant with allowance for float to control whip/maintain close axial alignment.
 

proppastie

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There was a whole lot of work and analysis in that design....I did not closely study it but was impressed with the detail and the amount of work and time that was expended. They have run it and planned more extensive tests.....which is perhaps different than some of the vendors that sell these types of items (leastwise what some have said here).....Given what I have seen of this design I think they might discover significant problems down the road and perhaps they would appreciate any suggestions one might have if you contact them.
 

Armilite

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There was a whole lot of work and analysis in that design....I did not closely study it but was impressed with the detail and the amount of work and time that was expended. They have run it and planned more extensive tests.....which is perhaps different than some of the vendors that sell these types of items (leastwise what some have said here).....Given what I have seen of this design I think they might discover significant problems down the road and perhaps they would appreciate any suggestions one might have if you contact them.
======================

Any idea on how to figure Belt Width needed for these common Engine Hp's? I have seen (3) V Belts on a 277, (4) V Belts on a 447, (5) V Belts on a 503. These newer Belts grab better.

277 28hp@6400rpm with some upgrades 35hp@6500rpm.

377 35hp@6500rpm

447 40hp@6500rpm

503 50hp@6500rpm

An (8) Groove Poly V PTO Pulley 60mm = 2.36" OD. 6500rpm/2750rpm = 2.36 Ratio.

70mm (2.8") x 2.36 = 165.2mm = 6.5" for Top Pulley.
65mm (2.6") x 2.36 = 153.6mm = 6.0" for Top Pulley.
60mm (2.36") x 2.36 = 141.6mm = 5.7" for Top Pulley.
55mm (2.17") x 2.36 = 129.8mm = 5.1" for Top Pulley.

This 8 Groove Belt Drive Prop Hub OD is 100mm = 3.94" so you would want Top Pulley OD to be at least 100mm OD or larger. If (4) 4pk Belts work for 80hp, I would think (2) 4pk Belts would handle up to 40hp.

Pulley Serpentine Belt 8 Grooves 0.67 _ 17mm ID  2.36 _ 60mm OD.jpg PROP HUB 100mm.jpg
 

proppastie

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Any idea on how to figure Belt Width needed for these common Engine Hp's? I have seen (3) V Belts on a 277, (4) V Belts on a 447, (5) V Belts on a 503. These newer Belts grab better.
In theory you should be able to study the manufacturers engineering data they supply.....But the easier way might be to hang out where lots of UL fly and talk to people...ask lots of questions .....like "how many belt failures have you had, how many hours do you get on a set of belts".....that assumes you have a very similar setup.....with TV or design issues all bets are off.
 

mullacharjak

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Since v belts can slip do they soften the interaction between the prop and engine or does one need a device to dampen tv as used in gear drives? Also would 5 3/8 inch v belts be enough to transmit 70 Hp.
 

rv7charlie

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Since v belts can slip do they soften the interaction between the prop and engine or does one need a device to dampen tv as used in gear drives? Also would 5 3/8 inch v belts be enough to transmit 70 Hp.
Sure. And the slipping generates heat, and heat will soften the belts, and....

To the questions about how many/what size belts are needed for X HP: If you look at mfgrs' application charts, they'll show torque specs for electric motors, single cylinder engines, 2 cyl engines, 4 cyl engines, etc. The spec changes with each drive source, because peak torque varies with drive source. The same belt might work at widely varying HP ratings, depending on drive type and rpm.
 

Armilite

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A Good Read on V Belts.
https://www.brighthubengineering.com/machine-design/64676-v-belts-types-by-size-classification/

"Here’s is a brief outline on the power transmitting capacity of the each section type of the belt. The exact transmission power of the belt will vary based on other criteria like arc of contact, speed ratio, etc."

Probably the most common V Belts used were B & C. I have seen 3, 4, 5 Belt Configurations used.

Section ‘A’ Type – 0.1 kW to 3 kW = (4.0hp) per Belt. (3) Belts for a 185UL or GX200.

Section ‘B’ Type – 0.5 kW to 6 kW = (8.0hp) x 4 = 32hp, 17mm(0.669") x 4 = 68mm

Section ‘C’ Type – 1 kW to 12 kW = (16.0hp) x 2 = 32hp, 22mm(0.866") x 2 = 44mm

Section ‘D’ Type – 3 kW to 32 kW = (42.9hp) 32mm

Section ‘E’ Type – 5 kW to 50 kW = (67.0hp)

The values above indicate the capacity of a single belt. In case a higher power is to be transmitted. The belt can always be coupled with more belts in series to transmit the required torque.

This Red Belt Drive selling on eBay uses (4) 4pk675 Belts like that other tall Belt Drive that was for 80hp. Each Belt has 4 grooves and is 14mm Wide. 80hp/4= 20hp each.
(1) 4pk = 14mm (4) Groove Pulley for 20hp.
(2) 4pk = 28mm (8) Groove Pulley for 40hp.
(3) 4pk = 42mm (12) Groove Pulley for 60hp.
(4) 4pk = 56mm (16) Groove Pulley for 80hp.
Industrial V Belts.jpg
Belt Drive eBay 1.jpg

4PK Belt is 14mm Wide.jpg
 

Armilite

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Since v belts can slip do they soften the interaction between the prop and engine or does one need a device to dampen tv as used in gear drives? Also would 5 3/8 inch v belts be enough to transmit 70 Hp.
==============================================
Almost every Belt Drive made today use those Poly V Belts. This Belt Drive was for an 80hp Engine using a 16pk Belt or (4) 4pk Belts. One 4pk belt is 14mm Wide. 80hp/4 = 20hp each. I'm sure there is a Saftey Margin. V Belts tended to Slip, so they went to Cog Belts, but most have went to Micro V Type Belts.

4PK Belt is 14mm Wide.jpg PPG BELT DRIVE 2.58 - 1.jpg
 

rv7charlie

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Again, a pure power number won't tell you what you need to know. You need to find the spec listed for *peak torque*. Some belt makers give an electric motor spec (I just saw one that specs 3 phase, and derates for single phase), and then derates in inverse relationship to number of cylinders. (Single cyl is the lowest HP rating.)
 

Armilite

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Again, a pure power number won't tell you what you need to know. You need to find the spec listed for *peak torque*. Some belt makers give an electric motor spec (I just saw one that specs 3 phase, and derates for single phase), and then derates in inverse relationship to number of cylinders. (Single cyl is the lowest HP rating.)
==================================

Yes, when they Dyno an Engine they measure Peak Torque then convert that Number to Hp. It depends on what the Belt Manufacture uses to rate their Belt, Torque or Hp. Like the Stock 277UL Dynoed Max 25.4hp@6000rpm = 22.23346666666667 Torque.

Torque and horsepower relations:
T = HP * 5252 / RPM
HP = T * RPM / 5252
RPM = HP * 5252 / T
* Torque values are in foot-pounds.

Old V Belts vs COG Belts vs the New Micro V Belts will be rated differently. I prefer to use the newer Micro V Belts. That one Belt Drive was designed for a PPG using a 600cc Motorcycle Engine making 80hp @8000rpm If I remember right. I'm sure they built in a Plus Factor using them (4) 4pk Belts or (1) 16pk Belt, but I do want to check their Work Numbers. 80hp/4 = 20hp per 4pk Belt x 2 Belts = 40hp which covers my goal of 35hp@6500rpm. I got my 8 Groove 60mm Pulley today, 60mm x 2.36 = 141.6mm is what I need for 2750rpm so I need to find that Size now or make one. Somewhere around here, I have a NOS 5 V Pulley, the one on the right. I'm wondering if I can maybe just turn it down and put the Micro V pattern on it. I don't remember the OD of it.

141mm/60mm = 2.35
142mm/60mm = 2.366666666666667 Ratio. 142mm OD = 5.590534"

DRIVE PULLEY 1.jpg

eBay: 7-1/4" OD 6061 T6 Aluminum Round x 8-1/4" Length - Lathe Bar Stock.
Brand New, enough for 2 Pulleys.
$102.30
7.25 Diameter 6061 T6 Aluminum Round  8.25 Length.jpg
 

Armilite

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Maybe use 7075 for Top Pulley. If (2) 4pk Belts are 28mm the 8 Grove Pulley I got is 1.5" Wide = 38.1mm. Center Hole is 7/8" = 22.225mm, so can be Bored for Rotax's 30mm 1:10 Taper or for a Honda GX390+ 1.0" Shaft.

7" Diameter 7075 T651 Aluminum Round Bar Stock 7" Dia x 5" Length.

Brand New $99.00

7" Diameter x 2-1/4"-Long 7075 T651 Aluminum Round Bar 7075.
Brand New $60.00
Bought 8 Groove Diesel Truck Alternator Serpentine Belt Pulley 2.37O.D .875  ID - 2.jpg Bought 8 Groove Diesel Truck Alternator Serpentine Belt Pulley 2.37O.D .875  ID - 1.jpg Bought 8 Groove Diesel Truck Alternator Serpentine Belt Pulley 2.37O.D .875  ID - 3.jpg
 
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rv7charlie

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==================================

Yes, when they Dyno an Engine they measure Peak Torque then convert that Number to Hp.
<snipped>
Agree on the formula, but not on how power is calculated. We might be having a 'failure to communicate'. 'Torque peak' is not the same thing as 'maximum torque'. And maximum torque always occurs at a lower rpm than an engine's maximum HP rpm. And I believe that RMS torque is used to calculate HP. And...in a pair of engines with exactly the same maximum torque, peak torque on a single cylinder engine will always be higher than peak torque on a 2 cyl, or 4 cyl, and ***much*** higher than an 8 cyl engine.

Am I making sense, or do we need to agree to disagree?

Charlie
 

Armilite

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Agree on the formula, but not on how power is calculated. We might be having a 'failure to communicate'. 'Torque peak' is not the same thing as 'maximum torque'. And maximum torque always occurs at a lower rpm than an engine's maximum HP rpm. And I believe that RMS torque is used to calculate HP. And...in a pair of engines with exactly the same maximum torque, peak torque on a single cylinder engine will always be higher than peak torque on a 2 cyl, or 4 cyl, and ***much*** higher than an 8 cyl engine.

Am I making sense, or do we need to agree to disagree?

Charlie
=======================================

Yes, I agree with your statement, but for here, Homebuilt Airplanes and Ultralights were mainly discussing Engines that make 15hp to 65hp which are usually 2 Stroke 1 Cylinder Engines for Ultralights to make Part 103 Weight and 2 Cylinder 2 Stroke Engines and these Small 4 Stroke Industrial Honda/Clone Engines which are also Single Cylinder and V Twin 2 Cylinder or a 1/2 VW Type. While there are a few 3 Cylinder 2 Strokes, very few people use them and they usually use a Gear Drive on any 2 Stroke over 65hp. Ever see a Belt Drive on a 618UL (73.4hp), a Rotax Rick 670 (92hp)? Hirth's largest engine that uses a Belt Drive is the F-23 (50hp). The Larger, 4 & 6 Cylinder, 4 Strokes are usually run Direct Drive account their Certified Airplane Engines and were Designed for that! Is there 4 Cylinder Subaru's, 6 Cylinder Corvairs, Chevy V6's and V8's out there, Yes, but very few. As humans, we relate to Engines in HP, not Torque, just as we relate to Compression Ratio: as Theoretical 11.8cr, not effective 6.7cr. People understand better when you say I have 11.8cr and I'm having Detonation problems. Peak Torque and Peak Hp always happen at different rpm.

Stock ROTAX 277UL with MUFFLER VS 277UL with R&D TUNED PIPE. You can see the Peak Toque and Peak Hp are at different rpm.
ROTAX 277UL MUFFLER VS R&D TUNED PIPE.jpg
 

n3puppy

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Like Dino said, lots more involved in calculating a belts HP rating than simple Hp/Torque numbers - Things like Wrap angle, length, etc are very important

Gates has a windows software package available to calculate HP rating of drive systems - I can't download it because I use a tablet.
From this Gates website
https://gatesbeltsandapplications.blogspot.com/2013/02/horsepower-ratings.html

Determining a belt’s HP rating requires more than just knowing the belt type. Speed, pulley sizes, belt length, wrap angle, and other factors affect the HP rating. Speed affects the HP rating because as speed decreases, torque increases, so the HP rating must also decrease. Larger pulleys improve the belt’s HP rating because less tension in the belt is needed to transmit the torque. Synchronous belt HP ratings are based on having at least 60° of wrap and 6 teeth in mesh. V-belt ratings increase as wrap increases. HP ratings also include a length correction factor. Longer belts have higher HP ratings because they are used with larger pulleys and/or larger center distances, which decreases bending fatigue in the belt.

The easiest method to calculate a belt’s HP rating is by using our software Design Flex Pro or Design IQ. You can also use the tables and equations in our Drive Design Manuals.

Belt horsepower ratings are used for designing belt drives. Always remember to design a drive with an appropriate service factor based on your application.
 
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