# Hybrid trikes

Discussion in 'Motorized Trikes' started by jawnn, Jun 8, 2009.

1. ### jawnnMember

I want to build a "gas-ellectric hybrid" power system....:idea:

I need info about what size engine to run what size generator to power a hub motor (or possably a small electric) for my trike.

I hope not to need a batterys, or use very small ones...

Is there an expert in electrics out there?

Last edited by a moderator: Jun 9, 2009

2. ### loquinActive Member

jawnn, I assume you still have the same constraints as in your earlier thread?
400 pounds, 14% slope? What is the average percentage of time where you will be climbing hills, compared the time when you'll be going downhill/level?

A no-battery situation is probably not feasible. This is because the electric motor you will need is on the order of 1500 watts (2 HP.) Small DC alternators/generators are on the order of 50% efficient, so, you would need at least 4 horsepower to push the bike up hill when using this approach. So, you're looking at approximately a 160cc Honda or equivalent. Note that this doesn't address the controller efficiency or the DC motor efficiency. (A good controller is about 90% efficient - a good motor about 80% efficient. 90% times 80% = 72%, so the SYSTEM efficiency is on the order of 36%. Meaning that you would actually need 4200 watts from a motor, or approximately 5.6 HP...:icon_cry On the plus side, no power is needed when going downhill, and maybe 2HP when on the flat. (those efficiency losses hurt.)

So, let's move away from your motor - generator - motor, no battery option. We'll add batteries to supplement a smaller gasoline motor when going uphill and accelerating. Generator voltage will drop as the load increases, to the point that the battery voltage is higher than the generator voltage, and it (the battery) is thus providing the bulk of the current when climbing, supplementing the power.

A smart controller will take the power generated as you go downhill, and pump it back into the battery (about 25% of it, anyway, when accounting for efficiency losses) So, the motor would need to replace about 75% of the power used in hill climbing. If you have a series of hills, where you go up, then down hill, you are looking at a 50% 'duty cycle.' (actually probably somewhat higher than this, as you can go downhill faster than you went up hill...) But, we assume 50% for the moment. This means that your generator will provide 100% of it's rated output when going uphill, and at least 75% going downhill (to recharge the battery) But, with the generator at about 50% efficiency, and the charger at about 70% efficient, only about 35 % of the power from the motor actually gets stored in the battery. To recharge the 75% of the power used from the battery when climbing in the same amount of time as when climbing, the motor would need to run at about the same power level as that needed for climbing.

Lets assume that the motor/generator set can supply half the power for the climb. (and, you have a 3 HP motor spinning the generator.) The battery supplies the other half. And, you climb for 5 minutes, then descend for 5 minutes. So, the battery loses 3750 watt-minutes of power during the climb. When descending you regain about 940 watt-minutes by regenerative action. You would need 2810 watt minutes from the MG set and the charger. The 3 HP motor-generator-charger has the capacity to restore almost 3920 watt-minutes, so, the motor would need to run at 100% for a little more than 3 and a half minutes on the way back down.

However, since you're probably going downhill faster than you were able to climb, a 3 HP motor is what you would need for the worst-case scenario of a 'sawtooth' landscape, where you spend half the time climbing, and the other half descending.

If you intersperse level areas into the equation, the motor power requirements are reduced, so, you could probably get away with the 2.5 HP Honda.

However, alternators are are fairly heavy, and you're adding a gas motor to the mix. Plus, you'll need some batteries as well. Granted, not as much as a full electric solution, but they need to be thrown into the weight mix as well...

So, overall, this hybrid motored bike approach doesn't appear to be as efficient as a gas motor, directly driving the bike... (with a 2.5HP honda, coupled through a CVT, you would need 100% of the rated power during the climb, nothing on the descent, and about 50% available power when cruising on the flat.)
***
Hybrid auto systems are feasible, because as power goes up, so do efficiencies. And, a Prius, for instance, stores quite a bit of energy in it's batteries. Enough for 15-20 minutes of driving around. A 200 KW system is over 93% efficient, for instance. A 25KW generator system, similar to what a hybrid car would need, is probably on the 80% efficiency level. This larger storage capacity, coupled with higher efficiencies, tip the scales, so that it can be more efficient than directly driving the wheels with a larger motor.

Last edited: Jun 9, 2009
3. ### jawnnMember

100mpg contest

NPR radio is haveing a contest for the first 100mpg car, their restraints are a bit absurd but I think we should build a minamalist car any how. If not me some one else. http://www.progressiveautoxprize.org/

I don't under stand why some on can't get 100 mpg with a very lightweight trike (carbon fiber not essential). Does it really have to move faster than 30 mph on flat land?? Or is this contest about how to revitalize General Motors?

I think one could be built at less than 150 lbs even with an aerodynamic body. And one quarter HP from the driver may even help at that weight.

Some people think they can generate enough electricity by pedaling, but I don't think it is possible. I know of one person that is building small car that uses a gas engine to generate enough electricity.

And does a leaning trike waste less energy on the corners?

Last edited by a moderator: Dec 15, 2015
4. ### SimpleSimonActive Member

The Automotive X Prize compretition is a joke, and an un-funny one at that.

Every one of their criteria has been met and exceeded already by Robert Q.Riley, one of the worlds leading experts in alternative vehicle design. It's called the XR-3, and as designed is a diesel/electric hybrid two-seater (side by side) tadpole tricycle capable of freeway speeds and economy in the close neighborhood of 200 mpg, while meeting federal safety and equipment standards.

5. ### loquinActive Member

A person can generate about 1/6th HP on a long term basis (more for short spurts.)

Theoretically, yes, since it should allow you to take turns at a somewhat higher speed. So, less power is wasted in slowing down and then speeding back up to cruise speed.

Last edited by a moderator: Dec 15, 2015
6. ### jawnnMember

Mpg

If my trike weighs 75lbs and the cargo up to 40 lbs then the driver is about 290lbs and I add a power system that is around 100lbs hooked into the drive chain....will it be possible to climb a 12% grade with my existing gears with 425lbs????

The lowest of my gears are 10.58 gear inch and the second much easier to shift into is 16.47 gi what ratios these are I do not know.

Sounds like a simple 2-stroke air polluter is the most efficient. Even a 49cc engine with CVT would get HOW MUCH mpg???

I thought it was more like 1/4 hp but Im not suprised. Thats why I pedal so slowly.

Last edited by a moderator: Dec 15, 2015
7. ### cabinfever1977Member

my 48cc 2-stroke is getting 180-200mpg @ 30-35mph

8. ### loquinActive Member

4 stroke R/S or Honda pollute much less than most two strokes.

A gas system (with staton gearbox) weighs in at about 20 pounds. A belt CVT system with jackshaft, or a Nuvinci approach, a little more.

A recumbent peddles from the front, so the motor would need to be there in order to tie in to your existing gearing... Which would be impractical, to say the least.