How much HP does it take to cruise at 35mph?

[SecondMonkey]

I've had this crazy idea for a while about building a small trailer with an electric motor and batteries to use as a "pusher" for my Jeep. It would not provide full power, but I'm hoping I could use it up to around 35mph with regenerative breaking to recharge the batteries.

So my question is, how much HP is needed to propel my Jeep on flat ground at 35, 45, maybe even 55mph? The jeep weighs 3000lbs and is not very aerodynamic.

At 35mph, I'm at about 1200 RPMs, which equates to 60hp on my engine's HP curve. That said, I'm only giving it about 1/4 throttle. Would it be fair to guess then that I'm only using 15hp?

 

[rationull]

According to my scangauge (take the measurements with a grain of salt...) it takes around 13 hp to push my civic (~2700 lbs curb weight) along at 35 or 45 mph at around 2500 RPM.

FWIW...

 

[Shannow]

http://www.mrsharkey.com/pusher.htm

The reverse idea.

 

[SecondMonkey]

Yeah, that's kinda where I got my idea.

I may even add a 5-10hp diesel engines to help charge the batteries and give better range. I'd like to end up with a universal trailer I could hitch up behind any vehicle.

Ideally I'd love to install a small turbodiesel under the hood and make it into a hybrid - but the cost would far outweigh the gas savings.

 

[oilyriser]

Add an electric power steering pump and a vacuum pump for the brakes and vacuum operated doohickies, and shut down the motor when you're cruising on electric. The electric trailer can be wired to recharge the batteries using the power of the gas engine in the vehicle that's towing it.

 

[mpersell]

In the early 60's while at Ford, Robert McNamara found that 60 hp was all any passenger vehicle needed and tried to move Ford in that direction.

Next he got a government job and convinced JFK that given enough men, equipment and money you could win a land war in Asia and soon we were in Viet Nam.

 

[Camu Mahubah]

This used to be one of the the stats published by Road & Track in the eighties and nineties.

 

[SecondMonkey]

Does it make sense though, that 1/4 throttle = 1/4 hp output, as a rough estimate?

 

[SecondMonkey]

Originally Posted By: oilyriser
Add an electric power steering pump and a vacuum pump for the brakes and vacuum operated doohickies, and shut down the motor when you're cruising on electric. The electric trailer can be wired to recharge the batteries using the power of the gas engine in the vehicle that's towing it.


I'd really like to have an electric fan/water pump/PS/etc with no alt...but then reality creeps back in and I'd never recover the costs over gas.

I hate reality...

 

[Shannow]

Originally Posted By: SecondMonkey
Does it make sense though, that 1/4 throttle = 1/4 hp output, as a rough estimate?


Better (rough) estimate is manifold vacuum. Throttles are even less linear than vacuum.