# What motor for 400lbs

Discussion in 'General Questions' started by jawnn, Apr 15, 2009.

1. ### jawnnMember

What size of motor do I need for moving 400 lbs up a 14 percent grade?

Examples would be good to see.

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2. ### MountainmanActive Member

be glad to take a guess here

3 hp or aprox 47cc

ride that thing sideways

3. ### loquinActive Member

On the hills, torque is more important than HP...

14% is 8 degrees.

You need 56 pounds of 'thrust' to maintain a steady speed at an 8 degree grade pushing 400 pounds. On a 26 inch diameter tire, that works out to 61 foot-pounds (60.67...)

Assuming zero losses in your gearing , with a 20:1 gear ratio, the engine must therefore be able to provide 3 foot-pounds of torque.

So, whatever engine you get, with fixed gearing, divide 60.67 time the total drive ratio to calculate the absolute minimum engine torque.

But, if you design a CVT based setup, you could make this work. If the total ratio was 18 to 1, a 2.5:1 CVT reduction at hi load conditions would make the effective gear ratio about 45 to 1.

and, going up hill, dividing 60.67 by 45 yields 1.3 foot pounds. (there are more losses with a CVT though, so you should count on about 1.7 foot pounds engine torque, at a minimum.)

For reference:

The Honda GXH50 is 2.5HP, 2.2 ft-lb max
The Honda GX35 is 1.3 HP, 1.4 ft-lb max
Mitsubishi TLE43 is 2.2 HP, 1.6 ft-lb max

Last edited: Apr 19, 2009
4. ### 5-7HEAVENGuest

If you are healthy enough to pedal a 21-speed bicycle, then a Honda x50 or 2.2hp Mitsubishi engine with 1.125" roller or corresponding gear ratio should be able to ASSIST you up the hill.

If you're not healthy or skilled enough to pedal uphill then you need a motorcycle.

5. ### seanhanMember

Thats just the engine , There is also the issue of the correct Bike.
Got to get them both right !!!

6. ### ZnsaneRyderMember

You will need stronger rims. If you get a 24-inch wheel bicycle, you can get plastic BMX wheels for it, and they are tough! I have one of those plastic 24's on the rear of my bike, even though it's a 26-inch bike, because I kept breaking spokes often on my dirt road.

Also, you may need low gearing and sacrifice speed for torque. You could also look around for a bigger engine. My bro's 2.5HP (79cc) trailer can a 300lb person, with cargo on the trailer. If you demand more power for hills, the best option is a 6.5HP Honda Clone engine. I can take any hill with mine.

7. ### duivendykGuest

I don't think a 50cc or smaller engine is going to cut it, you need at least a 50:1 reduction,which means doing 8mph going up that grade at 5.5k rpm (max torque) so you wont be able to do much over 10 mph without a gearbox or a CVT.So it's a CVT and/or a larger engine (100cc plus), preferably both

8. ### iRide CustomsMember

Nothing seen on this site would be what you need. I think you might want to go the way of an actual motorcycle. 14% grade is quite steep and if you plan on going down as well, you'll need something with substantial brakes.

9. ### duivendykGuest

Admittedly,it presents problems,I live in a place with 10% grades and manage to get up&down with a Mitsu/Staton/NuVinci setup (pricey).Even with that wide 3.5 ratio range my top speed is only around 25 mph.I cruise at around 18-20.You need the best brakes you can get.Brake fade can be dangerous on long steep descents!!.

10. ### MountainmanActive Member

not to be discouraged

not to be discouraged
with a little studying I think that you will find just what you need

when I owned a bicycle shop years ago
we sold a few bikes to ones close to your weight

and now days we have many experts making
things such as heavy duty wheels

a nice strong frame
aprox 50cc Japanese engine
direct chain drive
with some low gearing

should put you close -- I would think ???

ride that thing sideways

11. ### 5-7HEAVENGuest

At the entrance to my workplace's parking structure is a very steep ramp. There is a barrier arm that raises and lowers with every car entering the lot. There is no room to get a running start and I must wiggle past the arm, which is exactly where the ramp begins.

With twin engines, friction drive w/1.25" and 1.5" rollers and 5th gear of a 7-speed bike, I am able to tackle this steep ramp from a standing start.

With the same twin engines/friction drive on a single-speed cruiser, it is impossible to climb this ramp from a standing start.

That's with a 90 lb. bike, 25 lb backpack and 200 lb. rider.:detective:

12. ### loquinActive Member

Using a single speed motor, the gearing would need to be about 45 to 1 to get 400 pounds up a 14 % slope, with a Honda GXH50 engine, and about 50 to 1 with a Mitsubishi. But, that also limits your top speed to about 12 miles per hour! Single-speed motor-driven bike solutions are always a compromise between top end, and hill climb/acceleration.

In order to use a single engine, (less than 50cc,) you would need to have a means of changing the gear ratio if you want a reasonable top end, and still be able to climb that kind of slope, pulling that kind of weight. That's the reason that I mentioned a CVT. A CVT can automatically shift to a higher ratio as the load increased when you are going up hill, allowing the motor to operate in it's peak torque range. And, it can shift to a lower ratio as your speed increases, allowing a decent top-end. But, it isn't the perfect solution. It does cause some additional efficiency loss - a CVT and a jackshaft solution would lose about 10% of the available power when the belt is new, and progressively lose more as the belt wears.

Since CVT belt wear is important to the system efficiency, you need to make sure that your system isn't geared too tall to keep the CVT from shifting completely into the lowest gear ratio when you get up to speed. (If you don't the belt will wear faster.)

You would also want to use a motor which has a high torque output - 4-stroke motors tend to have higher torque, over a wider range than do 2-stroke engines.

13. ### jawnnMember

I just need some links to these motors....and it may have to be electric if I can't find one small enough to fit back of the seat with out sticking out the rear.

14. ### 5-7HEAVENGuest

Function before form.:detective:

Remember, you're trying to push 400lbs. up a 14% grade. You don't have many options.

15. ### duivendykGuest

Come to think of it a GP 460 might do the trick for you,about 45cc,a real screamer,is good for 4.5 HP !! at 9000 rpm,a CVT would be nice to have though.Look at the CVT section for more info.

16. ### stude13Active Member

you might try hooper imports, the sell honda 50 and 70 and larger knockoffs. i have a 70 that has 49 stamped on the barrel. it is a three speed auto. these motors werer used on honda step through frame mopeds in from the sixties.

17. ### 5-7HEAVENGuest

On second thought, a NuVinci hub and a Mits 43cc or Honda X50 should do the job.

And of course the engines will stick out like a sore thumb.:whistling:

18. ### duivendykGuest

Of course including a Staton gear box also.Has enough reduction, but pretty slow on 14% incline,the only remedy for that is more power.Can the GP 460 be married to the Staton box ?.I believe so ,but not 100% sure.Not cheap.

19. ### macarolloGuest

196cc honda clone from Harbor freight.... You'll get up that hill no problem!

20. ### 5-7HEAVENGuest

This guy could use a push trailer like macarollo's suggesting. Maybe 2.5hp.:idea: