flybouy
01-16-2017, 09:17 AM
I see a lot of these posts on this forum and have read some excellent, and some not so excellent advice. So just going to throw out some advise from an old gearhead that's had a few years of experience. First, a little review on the gearhead chalk board.
Horsepower - 2 ratings: 1 at the crankshaft, 2 at the driven wheels.The manufacturers advertise the rating at the flywheel because it's larger, both ratings are maximum or peak (as in the peak on the graph before it falls off). What they don't advertise is the RPM that the peak hp shows up. For gasoline fueled it's typically over 3,500 rpm and may be up to 5,000 +, diesel is typically below 3,000 rpm.
Torque - gas fueled engines again are peaked out at higher rpm vs diesel. Typically diesel fueled engines have a greater hp/torque ratios and operate at lower rpm ranges which results in longevity and greater fuel economy.
What does this mean? Well if a prizefighter's punch was rated this way the HP would be how fast he can throw the punch with no regard to impact. The Torque of the punch would be how hard the punch would impact.
Transmissions - they transmit the engine power to the drivetrain. The purpose of the gearing is to mach the specific engine to the specific task. One ratio for inertia from zero movement to one speed, from that speed to another speed, etc. If you have ever ridden a bike with gears you know that you need need a different ratio to pedal up hill that on level ground. When yo shift into a "lower gear" to pedal uphill your legs must go faster to maintain the same speed, just as your vehicle downshifts and the engine speeds up to do the same.
The differential gearing is is a ratio of how many times the driveshaft must rotate in order for the drive wheel to rotate one time. Just like that bike, the sprocket on the pedal is different than the sprocket on the wheel.
Now, given this long winded dissertation I hope this may help some folks understand what all those numbers mean. Fair warning, don't dwell on these numbers! When it comes to towing that is a very small percentage of the numbers that you need to get a clear understanding of what I can or cannot tow. Whats that you say? "I have the weight of the towed object what else would I need?"
Towed object information - yes weight is a major factor but how about the drag coefficient? That's the wind resistance the object presents. Remember as a child when you stuck your hand out of the window? Recall (other than your parents yelling at you) that when your hand was parallel to the horizon the fore against was was lot less than when your hand was vertical? Same physics apply, a 3' high tent trailer will offer lower wind resistance than a 13' fifth wheel. Then there's the parasitic drag, the side wall surface area that not only presents drag in a forward motion but acts like a huge sail surface during crosswinds whether from nature or a passing bus or semi rig. How about where the rubber meets the road? What's the number of tires on the ground? Two? Four? Six? What's the rolling resistance of those tires?
Lot's of calculations right? What's the consumer to do other than buy time on a super computer at MIT and run the numbers? My advice is to try it before you buy it. If your looking at a new trailer ask the dealer if you can hitch it up and go for a drive. Feel how it reacts to your truck and terrain and remember that this is best case scenario as the trailer will be at it's lowest weight until the day you empty it out to sell it. The reverse if your looking at a new truck, hitch it up to your camper and go for a spin. I know this is more challenging for the "fiver folks" but most people with 5 th. wheeler seem to be more experienced. I'm of the opinion that a number of folks asking the questions "will my truck pull this" already suspect it won't and are hoping against hope that someone will say it's O.K. I speak from experience, I've had the Chevy S10 that towed the pop up with ease and purchased a hybrid camper that was was within the tow weight. Lots of downshifting on winy days on level roads, white knuckled days in wind and passing trucks, then 1/2 ton and "now I can tow more" so repeat the process until 3/4 ton truck and 35' trailer.
So this is just my advice for what it's worth - try it, if the dealer won't let you try it out then seek out another dealer and you can't go wrong with going big on the tow vehicle. Excess capacity on the tow vehicle will add to the safety margin and facilitate the inevitable "We need a larger trailer" day that seems to haunt us all.
Horsepower - 2 ratings: 1 at the crankshaft, 2 at the driven wheels.The manufacturers advertise the rating at the flywheel because it's larger, both ratings are maximum or peak (as in the peak on the graph before it falls off). What they don't advertise is the RPM that the peak hp shows up. For gasoline fueled it's typically over 3,500 rpm and may be up to 5,000 +, diesel is typically below 3,000 rpm.
Torque - gas fueled engines again are peaked out at higher rpm vs diesel. Typically diesel fueled engines have a greater hp/torque ratios and operate at lower rpm ranges which results in longevity and greater fuel economy.
What does this mean? Well if a prizefighter's punch was rated this way the HP would be how fast he can throw the punch with no regard to impact. The Torque of the punch would be how hard the punch would impact.
Transmissions - they transmit the engine power to the drivetrain. The purpose of the gearing is to mach the specific engine to the specific task. One ratio for inertia from zero movement to one speed, from that speed to another speed, etc. If you have ever ridden a bike with gears you know that you need need a different ratio to pedal up hill that on level ground. When yo shift into a "lower gear" to pedal uphill your legs must go faster to maintain the same speed, just as your vehicle downshifts and the engine speeds up to do the same.
The differential gearing is is a ratio of how many times the driveshaft must rotate in order for the drive wheel to rotate one time. Just like that bike, the sprocket on the pedal is different than the sprocket on the wheel.
Now, given this long winded dissertation I hope this may help some folks understand what all those numbers mean. Fair warning, don't dwell on these numbers! When it comes to towing that is a very small percentage of the numbers that you need to get a clear understanding of what I can or cannot tow. Whats that you say? "I have the weight of the towed object what else would I need?"
Towed object information - yes weight is a major factor but how about the drag coefficient? That's the wind resistance the object presents. Remember as a child when you stuck your hand out of the window? Recall (other than your parents yelling at you) that when your hand was parallel to the horizon the fore against was was lot less than when your hand was vertical? Same physics apply, a 3' high tent trailer will offer lower wind resistance than a 13' fifth wheel. Then there's the parasitic drag, the side wall surface area that not only presents drag in a forward motion but acts like a huge sail surface during crosswinds whether from nature or a passing bus or semi rig. How about where the rubber meets the road? What's the number of tires on the ground? Two? Four? Six? What's the rolling resistance of those tires?
Lot's of calculations right? What's the consumer to do other than buy time on a super computer at MIT and run the numbers? My advice is to try it before you buy it. If your looking at a new trailer ask the dealer if you can hitch it up and go for a drive. Feel how it reacts to your truck and terrain and remember that this is best case scenario as the trailer will be at it's lowest weight until the day you empty it out to sell it. The reverse if your looking at a new truck, hitch it up to your camper and go for a spin. I know this is more challenging for the "fiver folks" but most people with 5 th. wheeler seem to be more experienced. I'm of the opinion that a number of folks asking the questions "will my truck pull this" already suspect it won't and are hoping against hope that someone will say it's O.K. I speak from experience, I've had the Chevy S10 that towed the pop up with ease and purchased a hybrid camper that was was within the tow weight. Lots of downshifting on winy days on level roads, white knuckled days in wind and passing trucks, then 1/2 ton and "now I can tow more" so repeat the process until 3/4 ton truck and 35' trailer.
So this is just my advice for what it's worth - try it, if the dealer won't let you try it out then seek out another dealer and you can't go wrong with going big on the tow vehicle. Excess capacity on the tow vehicle will add to the safety margin and facilitate the inevitable "We need a larger trailer" day that seems to haunt us all.