Worm Gear Efficiency

What is the speed of the bike on plain road, at the same gear setting that you use for climbing the inclined terrain?

about 7km/h

It appears that there are lots of transmission loss in your gear drive. The ratio of the gear drive may not be optimum/right. I am sure our automotive experts will have right solution to the problem at hand.

So, one might desduce that the worm drive is rather less efficient than the chain drive. Why is the worm gear present in the first place?

The engine's rpm is 7000, on the drive shaft's edge is a 9 tooth sprocket, that drives by chain a 32 tooth sprocket, and this is the input to the worm gear.

7000 * 9 / 32 = 1968.75 /30 = 65.625 (Revolution Per Minute) RPM

The final RPM of the cycle wheel = 65.625

What is the circumference of the cycle wheel? (3.141 * Diameter of the wheel) = Distance travelled in a minute by your bike.

Bike speed works out to 7.296 Km PH (That is close to your 7 Km PH)

I know nothing about bikes. I hope, somebody soon will join us.

My hunch is that RPM is not right. Cross your fingers & wait...

The final RPM of the cycle wheel = 65.625

The bike would certainly have to have several speeds (step up) between the bottom bracket (pedal shaft) (for which 65 rpm would be a reasonable pedaling cadence) and the rear wheel. A bike with a top speed of 7 km/h would be almost unrideable. I'm a pretty old and feeble, but can pedal at 30 km/h on the level, using about 1/6 hp.

I suggested to reduce the input speed to about the half.

The bike is a new one, so all the sprockets and cogwheels are new .

The clutch is designed to disengage at 4000 rpm- This might be aproblem for itself!

I'm not talking about climbing a hill, just begining a short slope of few meters.

I think that I'll try to test the set, by using temporarily an e-motor with less power and slower-about 1000 rpm.

If you are loosing most of 1 hp in the gearbox it should get noticeably warm rather fast.

How heavy is the bike and how heavy is the rider and how steep is the hill?

If your engine puts out 1 HP at 7000 RPM the odds are it probably doesn't put out much over 1/4 or less at 1800 - 2000 RPM.

So who are the engineers you are talking to? They don't sound like they are all that knowledgeable?

a worm gear is ineffient. use sprockets or belts if possible.

I would have to ask what is the torque rating of the engine. In my experience a small 1hp engine is not capable of much more than pushing a bicycle along on level ground ONCE it is moving.

I've seen some incredibly small engines and motors that can claim 1 hp but couldn't move a fart under load conditions.

Don't you think that not only power output [hp or kw] is relevant, the speed which come thourh gear is not less crucial!

LOL its Monday and I try not to think.

In my overly simple world torque is what gets you going.

You can tell the muscle car. He squeels his tires without revving the engine up first. Pure raw torque overcomes the friction holding the wheel still and sqeeeelllllll

The rice grinder revs up to 11,000 and dumps the clutch to get the same effect.

The Tesla....... Ok I won't go there its electric.

Or in an old shop trick. Chuck the engine in a vice. Break off a broom handle. Bolt a pully onto the output shaft of the engine. Start engine and bring up to your desired running speed. Wedge broom handle under work bench and press against the rotating pully. if you can press hard enough to stall the engine then you probably don't have enough engine for the job.

Before I worry about the drive train I want to be sure I have the power.

I hope this helps!

I would have to ask what is the torque rating of the engine.

Or better yet, look at a torque curve. The little Honda GX25 is probably fairly similar, and has a fairly flat torque curve from 4000 - 8000 rpm with max power at 7000 rpm. Probably, if speed dropped to 3000, torque would drop by half, and at 2000, it might be 1/4. For moving something as large as a person, the engine should be kept running between 4000 and 8000 rpm.

With a 200 lb rider/bike total, a 15% grade would require 30 lb tractive force. Assuming a 1' radius wheel, 30 ft lb torque would be required. The engine produces .75 lb ft, so a total reduction of 40:1 would be required. At 7000 rpm, the wheel would turn at 175 rpm. With a wheel circumference of 6.28 feet, that would be 1099 fpm. This would be .208 mile/min, or 12.4 mph.

The bike would clearly need multiple gear ratios, because 15% is not the steepest grade likely to be encountered. Three speeds would work ok: the 12.4 speed gear would be the mid range. A lower range to allow for steeper grades (say up to 30%) would permit a speed of 6.2 mph, which would be fast enough for fairly easy balancing. A higher range would allow for a 25 mph top speed, and the ability to climb a 5% grade with a little left over to overcoming rolling resistance and a little air resistance.

The ratio (of ratios) from lowest to highest would be 4. This is a little more than a cheap CVT can supply, but a cheap CVT combines (and automates) the clutching and gear change functions, making for very simple riding and easy parts sourcing.

These CVTs operate at about 2.8:1 down to 1:1. So a compromise secondary ratio of 20:1 would permit grade climbing of about 20% and a top speed (on the level) of about 25 mph.

Many years ago used to have a moped that would do 30 on 1.3 hp (I weighed about 110 lb at the time) with two speeds. On very steep hills you helped it along by pedaling.

Yes your calculations are really profound, but the fact is that the bike didn't climb this short slope even with the lowest of 21 gear!

So I think that all your calculation were irelevant.

If I'll not be able to solve this problem through a mechanical device, I'll return to my original plan, to drive an alternator with the gas engine, and the alternator will supply electricity to a 500w e-motor.[which is baned in Israel!]

But curiousity is not only on march- it lies in me, and I'm eager to understand why the honda gx25 engine isn't sufficient with 70 rpm of the bottom crank with the lowest of 21 gear to drive the bicycle up a mild slope?!

So I think that all your calculation were irelevant.

The calculations have always worked in the past. There is no magic involved here, is there?

But curiousity is not only on march- it lies in me, and I'm eager to understand why the honda gx25 engine isn't sufficient with 70 rpm of the bottom crank with the lowest of 21 gear to drive the bicycle up a mild slope?!

The GX25 has been used on bicycles many times. So you'll have to do some testing.
At this scale things are easy to measure. You can measure actual HP of the engine with a simple dyno to see that the engine is working right. You can measure the efficiency of the worm gearbox (which appears to be the likely culprit) by measuring its operating output torque given the verified input torque produced by the engine.
You need to know what is the actual measured grade of the hill is? What is your weight? What is the weight of the entire contraption? What is the actual torque and rpm output of your engine? What are the losses through the worm gearbox -- you have to measure this because they can range from 2% to 50%, depending upon design and condition.

With a disc brake or permanent magnet motor (or hydraulic motor) as a load and a beam style torque wrench (or spring scale, etc) it is easy to set up a dyno to measure where the losses are.

The engine > generator > controller > motor > gear reductions path provides even more opportunities for losses.

Dear friend- I really appreciate your profound answer,

and I came by my self to the idea to test the bike's components, but my bike has a tweak brake, can I use it to measure the losses?

My weight is 87 kg, the bike with all the engine and gears is about 23 kg.

The slope is about 8%, but only few meters long.

The worm gear is NMRV30, do you know this gear?