Menu
Forums
New posts
Search forums
What's new
New posts
New media
New media comments
New profile posts
Latest activity
Media
New media
New comments
Search media
Members
Current visitors
New profile posts
Search profile posts
Log in
Register
What's new
Search
Search
Search titles and first posts only
Search titles only
By:
New posts
Search forums
Menu
Log in
Register
Forums
Cattle Boards
Trucks, Tractors & Machinery
Diesel Trucks
JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an
alternative browser
.
Reply to thread
Help Support CattleToday:
Message
<blockquote data-quote="Saltydawg" data-source="post: 156251" data-attributes="member: 2944"><p></p></blockquote><p></p><p></p><p></p><p>Your explanation of HP was a decent one, however HP is an expression of how quickly work is being done <strong>for a given torque level</strong>. HP, in no, way, shape or form can be used to determine how much work can actually be done, only how quickly it can be done. Torque governs how much work can be done.</p><p></p><p>Rod[/quote]</p><p></p><p> </p><p> Diesel engine...500lb/ft @ 2500 rpm peak torque.</p><p></p><p> Gas Engine.....300lb/ft @ 5500rpm peak torque.</p><p></p><p> Plugging these into the formula we get 238hp for the diesel and 285hp for the gas.</p><p></p><p> Ok so we have loaded truck we need to move down the road at 60 mph.</p><p></p><p> Lets say it takes 1000lb/ft of torque at the rear wheels to move this truck down the road at 60mph and we are using 31 inch diameter tires.</p><p> We need to spin those tires at roughly 650 rpm to maintain this speed.</p><p></p><p> Since neither of our motors make a raw 1000lb/ft of torque we are gonna have to use gearing to bump up the torque at the rear wheels.</p><p></p><p> Since the diesel makes 500 lb/ft of torque we are gonna need to use 2:1 gearing to get the required torque. Easy enough.</p><p> However we also need to keep in mind the speed of the vehicle....we need to keep those rear wheels spinning at 650 rpm.</p><p> Because of the 2:1 gearing our engine is still running at 2500 rpm's but our tires are now spinning at 1250 rpm....TWICE as fast as we need to go.</p><p> So we either lower the engine rpms or change the gearing.</p><p> Since we are concerned with total ammount of work these engines can do we will leave the engine run at 2500 rpm for peak torque and change the gearing.</p><p> Since we need 650 rpm's we need to cut the rear wheel rpms in half again.....so we bump up our gearin3:1.</p><p> What this also does is further multiply the torque.</p><p></p><p> We are now running 60 mph down the road, our engine is turning 2500 rpm and we have........1500lb/fttorque available at the rear wheels.</p><p> Not too shabby.</p><p></p><p></p><p></p><p> Now for the "little" gas motor.</p><p></p><p> It makes peak torque at 300lb/ft of torque at 5500 rpm's.</p><p></p><p> Again we need to increase gearing to get the minimum 1000lb/ft to move our loaded truck.</p><p> We need 3.33 gearing to reach our 1000b/ft.</p><p> However this still leaves our rear wheels spinning at 1666 rpm's....way to fast for our 60 mph goal.</p><p> Time to increase gearing again since we want to leave the engines at peak power output.</p><p> We need to add another 2.56 gearing to reduce the wheel speed to 60 mph....so now we are at a total of 5.89 gearing which increases are torque at the rearwheels to......1767lb/ft of torque.</p><p></p><p> So the "little" gas motor, thanks to its higher rpm and ability to better utilize gearing, has 267lb/ft MORE torque available at the rea wheels while moving the same load down the road.</p><p></p><p></p><p> The reason people use diesels however is because no motor lives long when it's run at 5500 rpm like our little gas job. They also get crappy gas mileage when run this way.</p><p>[/QUOTE]</p>
[QUOTE="Saltydawg, post: 156251, member: 2944"] [/quote] Your explanation of HP was a decent one, however HP is an expression of how quickly work is being done [b]for a given torque level[/b]. HP, in no, way, shape or form can be used to determine how much work can actually be done, only how quickly it can be done. Torque governs how much work can be done. Rod[/quote] Diesel engine...500lb/ft @ 2500 rpm peak torque. Gas Engine.....300lb/ft @ 5500rpm peak torque. Plugging these into the formula we get 238hp for the diesel and 285hp for the gas. Ok so we have loaded truck we need to move down the road at 60 mph. Lets say it takes 1000lb/ft of torque at the rear wheels to move this truck down the road at 60mph and we are using 31 inch diameter tires. We need to spin those tires at roughly 650 rpm to maintain this speed. Since neither of our motors make a raw 1000lb/ft of torque we are gonna have to use gearing to bump up the torque at the rear wheels. Since the diesel makes 500 lb/ft of torque we are gonna need to use 2:1 gearing to get the required torque. Easy enough. However we also need to keep in mind the speed of the vehicle....we need to keep those rear wheels spinning at 650 rpm. Because of the 2:1 gearing our engine is still running at 2500 rpm's but our tires are now spinning at 1250 rpm....TWICE as fast as we need to go. So we either lower the engine rpms or change the gearing. Since we are concerned with total ammount of work these engines can do we will leave the engine run at 2500 rpm for peak torque and change the gearing. Since we need 650 rpm's we need to cut the rear wheel rpms in half again.....so we bump up our gearin3:1. What this also does is further multiply the torque. We are now running 60 mph down the road, our engine is turning 2500 rpm and we have........1500lb/fttorque available at the rear wheels. Not too shabby. Now for the "little" gas motor. It makes peak torque at 300lb/ft of torque at 5500 rpm's. Again we need to increase gearing to get the minimum 1000lb/ft to move our loaded truck. We need 3.33 gearing to reach our 1000b/ft. However this still leaves our rear wheels spinning at 1666 rpm's....way to fast for our 60 mph goal. Time to increase gearing again since we want to leave the engines at peak power output. We need to add another 2.56 gearing to reduce the wheel speed to 60 mph....so now we are at a total of 5.89 gearing which increases are torque at the rearwheels to......1767lb/ft of torque. So the "little" gas motor, thanks to its higher rpm and ability to better utilize gearing, has 267lb/ft MORE torque available at the rea wheels while moving the same load down the road. The reason people use diesels however is because no motor lives long when it's run at 5500 rpm like our little gas job. They also get crappy gas mileage when run this way. [/QUOTE]
Insert quotes…
Verification
Post reply
Forums
Cattle Boards
Trucks, Tractors & Machinery
Diesel Trucks
Top