How to climb big hills with original GEBE kit?

[MtnGoat]

Anyone using the EHO35 35cc Robin/Subaru Mini-4? Does it compare favorably to the Tanaka 3300 for hill climbing ability?

The GEBE website claims: "Pull even heavier loads up steeper hills. Additional torque and muscle of this engine allows you to Hit the Trails off-road!" Of course the statement is comparative without an object of comparison. Additional torque compared to WHAT? Steeper than WHAT?

 

[Hive]

Read GEBE

Descriptions carefully. I believe the Tanakas are thought to be the more torqy engine, and will do better job on hills, and they are lighter. The 33 is excellent; its bigger brother, the 40, must be over powering.

I think the torque values are given for all engines, as is the HP at a given rpm, but torque is what counts and 2-cycles are generally known as the higher powered grinders. Clutch size also makes a diff. The 33 is way better and quicker than a 25, with 33's larger clutch and torque ratio.

I noted the difference immediately on my hill, over the 4-stroke 25. Figure rise to be a 300 foot rise in half mile, perhaps a bit more or a bit less.

 

[MtnGoat]

So I went to the respective manufacturer websites and found the specs. All torque values @ 5000 rpm.
Tanaka PureFire33cc - 1.16 ftlbs, 1.6 hp, 6.1 lbs
EHO35 35cc Robin/Subaru - 1.30 ftlbs, 1.6 hp, 8 lbs
Tanaka PureFire 40cc - 1.5 ftlbs, 2.2 hp, 8.2 lbs

Seems that little 4 stroke really delivers. Pretty light too.

Haven't been able to find any specs on my GZ25N 25.4cc Komatsu Zenoah/RedMax for comparison purposes. And how do you factor in clutch size?

 

[Hive]

Good Work, Good Research

(You meant to type "little 2-stroke," right? Or, referring to the Robin 4? It does it, but at 8 pounds and why I went with T-33.)

I went through the same process with both engines that I used, but then, I did not have the benefit of this board the first go 'round.

Clutch size? I believe all the 2-strokes (maybe not your 25 though) and the larger 4-strokers sport the large clutches, so it is not a significant factor, being only two sizes. The data you obtained seems to answer your questions in that respect.

Frankly, if the 25s had larger clutches, they would do a better job hill-climbing, I believe, judging from my experience with the Honda 25. Save the problem on the hill with that cruiser, I really liked the engine. In fact, to be honest, if I had a 24-gear bike at the time, it probably would have been fine. But, here I am with the little T-33. I like it also, save the higher decibels and gas mix. Will stay with it, though. Light, and hot, after I get it going.

Like I mentioned, I put the bike in (don't know gearing) small chair ring and smallest rear gear and then pedal with motor and it goes perfect, and even goes well without pedaling for a bit. There is room for faster spinning and lower gears if needed, but I do not need to use lower gears. Hill is about .5 mile long.

I still believe the big Tanaka may be too much power in the wrong hands. It is more than adequate for most inclines and too much if level surfaces are the main course, but that is just my view.

Then, there is the fuel consumption matter.

If you feel the bigger engine is what you need, by all means, go for it.

But, remember, the 2-cycles like high revs to stay clean and efficient. If a T-33 will do the job with a bit of pedaling, why not?

Either way, pedaling will likely be necessary, so it seems, the choice will be what you are personally comfortable with as a motor assist on hills.

If your 25cc KZ will handle them with a bit of pedaling in right gear, why not? But, if clutch slips or you need to put lots of work in it, then maybe a change to one you prefer is in order. You have all the data, save actually running one.

BTW, thought the GEBE site had some KZ specs up.

 

[MtnGoat]

(You meant to type "little 2-stroke," right? Or, referring to the Robin 4? It does it, but at 8 pounds and why I went with T-33.)...

BTW, thought the GEBE site had some KZ specs up.

Wow, they've got all the specs up for all the engines they offer! Didn't scroll down far enough. Thanks.

Because I have a KZ 25cc kit, I can use that for comparison. Looking at the difference in max torque values by percentage. I can get an idea of how much more climbing power I'd get. But the different size clutches (KZ has the 52 clutch) needs to be factored in as well. I don't know how to apply that factor. Is it just it slips or it doesn't?

I have to pedal like a madman or else the bike comes to a stop. It's 2200 feet up to my house from anywhere, over 4+ miles. Steepest section is 656 feet over .7 miles or 18%. Parts of that exceed 20%.

Actually I was referring to the 4 cycle 33.5cc Robin Subaru. Since it is a 4 stroke I would not expect it to be able to compete with the similarly sized 32cc Tanaka 2 stoke, but it does, with same hp and higher max torque. It does weigh more, but not that much more. It weighs less than the Tanaka 40cc. That Tanaka 33 is a particularly light one, even for a 2 stroke.

I still believe the big Tanaka may be too much power in the wrong hands. It is more than adequate for most inclines and too much if level surfaces are the main course, but that is just my view.

Then, there is the fuel consumption matter. ...

Which is why I was looking for some variable gearing solution when I started this thread. With a big power plant I can conquer the mountain, but I'd be overpowerd on the flats, at least for my sensibilites. After reading everything I can find on this forum for a while now, I realize the multi-geared solution only exists currently as a Nuvinci hub. I might just spring for a Staton with 35 Robin/Subaru and NuVinci hub. Expensive for sure. But you get a lot, including a custom built rear wheel, which I would have to add on to 40cc GEBE anyway.

I'm thinking I'll sell my current set up along with a new spoke ring and belt, and start saving. But I could try the Robin Subaru first with the GEBE kit I have, then convert to the Staton if it still doesn't make the grade. I doubt it will help enough. I'd probably lose in gearing what I gain in torque by going from 11 to 12 trail gear, and 24" to 26" wheel size. Wonder how many spokes I'd break during the experiment?

 

[OldPete]

From Denis at GEBE.

The Tanaka 3300 WILL pull the 14 tooth drive gear on flat level ground with little or no head wind.

The Robin Subaru 35 will just pull the 13 tooth drive gear givin the above conditions. I run my R/S 35 with the #12.

I laced my own rear wheel with 14g Wheelsmith spokes in a 4 cross pattern and wire tyed n' soldered the tyes. I wrapped the wire seven times at the last cross of the spokes. Both sides were tyed. I weigh 235# and ride fast n' free but do not charge over pot holes or curbs. I have yet to have any spoke issue.

 

[MtnGoat]

From Denis at GEBE.

The Tanaka 3300 WILL pull the 14 tooth drive gear on flat level ground with little or no head wind.

The Robin Subaru 35 will just pull the 13 tooth drive gear givin the above conditions. I run my R/S 35 with the #12.

Thanks for the real life comparison. I'm surprised to hear that, and a little disappointed I must admit. Higher torque rated engine of same HP rating can't pull as high gear. WTF? Why bother reading the specs.

From Denis at GEBE.
I laced my own rear wheel with 14g Wheelsmith spokes in a 4 cross pattern and wire tyed n' soldered the tyes. I wrapped the wire seven times at the last cross of the spokes. Both sides were tyed. I weigh 235# and ride fast n' free but do not charge over pot holes or curbs. I have yet to have any spoke issue.

I'm thinking the Tanaka 40cc is what I need to climb this mountain. Perhaps if I reinforce the spokes of my current wheel like you describe I could get by. Then again maybe the 40cc is just too much torque for the 14 ga. Thanks for the idea.

 

[OldPete]

The typical 14g Asian stainless steel spokes are not to be considered for powered bicycles. Use only DT or Wheelsmith ss spokes.

 

[Hive]

A Quick Thought

I bought a laced wheel from GEBE and it seems fine, but I have to admit, forgot the spoke gauge, then again, I use pedal-assist, and my hill is not that long; so, I are content.

I see the "mountain" pull is a big deal, so go for the 40 and deal with the added wheel cost, noise etc. No sense in getting upside down when unnecessary. Maybe even a 47, but not CA approved?

Better to go big, I guess I am saying, as you can always throttle-down; but if too small, you would have to buy bigger. I know, went through it.

Also, for me, I tried to match size and weight to power and the T-33 was the best choice - for me! These are bicycles, after all.

The T-40 and the larger 4-cycles were too bulky and to heavy. And inch or pound is not much, until you are pedaling mostly or have to sling the engine way aft because it contacts the seat. I am picky, however, and try to keep it all in perspective. If I was 30 years old, I would not think of a motored bike, save for canoe relay or and fishing relay. Easier to haul.

Clutch size is important and has to be big one to handle the torque.

Seems Dennis told me his preference is for the T-3300, but he might have changed his mind.

Common sense rules and you seem to have lots of it, so have a ball.

Be careful, with the NuVince plans etc that you don't spend more than you would have for a small motorcycle etc.

 

[Ray In San Jose]

Climbing medium hills with GEBE

I ride a stock EHO35 35cc Robin/Subaru Mini-4cyl GEBE setup on a mountain bike. I think my motorized bike setup has some hill climbing limitations which I am still exploring. My experiences might help you to decide how a larger engine setup could help you with your terrain.

See the attachments for my commute route. Essentially, it is a 15 mile commute, each way, with a maximum 6% grade. The very beginning of the grade chart shows 7.6% but that is really an artifact of the number and quality of gps samples. It is really 18% for about 100 feet.

I am an intermediate rider who built this bike off a Craigslist cheapie. I ride at the maximum 28mph, whenever I can, over poorly maintained city roads (dodging, but sometimes hitting potholes, rocks, glass...I have NEVER hit a shopping cart or garbage can in the road thankfully ). From stops and going up hills, I always pedal to help the motor. At times, I pedal very hard which, with the motor running, probably places extreme stress on the bike mechanical components.

I have about 1700 miles on the GEBE system.

Here are some of my observations of the MB setup -

* Early on, I replaced all the stock 14 gauge spokes with higher quality stainless steel 14 gauge spokes. Although the breakage rate went down, I am still breaking spokes. The latest breakage combination was 5 broken spokes with two adjacent. So, tying or soldering spokes together would not have helped. If you are planning to ride hard going uphill, I don't think 14 gauge spokes are going to make it. I am planning to try 12 gauge spokes as my next improvement step.
* Building a wheel with no dish. This doesn't give me enough added strength...still broken spokes.
* I replaced the hollow quick release axle with a standard steel one. After a few hundred miles, the steel axle became quite bent. I am now using a harder Chromoly axle. After 1200 miles, I noticed it is not quite as straight as new. But, the rims are not rubbing the brakes so it is still usable! I don't know what to do here. Chromoly is pretty hard. I am thinking this might be because bike components are not built for the extreme stress of added engine torque. Or, it could be because my bike does not have rear suspension and when I go airborne over road potholes, landing hard with the bike might be too stressful for the axle. Hilly terrain allows you to ride fast. If you also have poor roads, you may want to be aware of axle replacement as an added maintenance cost.
* As you observed, speed is an important aspect of how effective the GEBE works on hills. With the standard setup, the centrifugal clutch engages at 15mph. My total setup, including me, is about 220 lbs. Once the engine is engaged, the clutch will remain engaged at slightly lower than 15mph. For my weight and setup, the bike can pull me up grades of about 4% by itself. I am definitely pedalling at any extended grade of 6% or more. For 10% grades, the clutch is slipping a lot. For 18% grades, the rack mount engine makes the bike rear heavy and I can only pop wheelies on these slopes. So, 18% grade is the time I have to walk the bike. Because the engine clutch slips with steeper grades, I think the engine has plenty of power for my riding.
* Belt life is still an unknown. I posted an earlier entry regarding belt life. My 2nd belt is at 1000 miles and still going strong. On hills, keep the clutch engaged going downhill, or when coasting, slow to 15-20mph and engage the engine with authority. Otherwise, you will be investing in replacement belts.

So, with my experience on hilly terrain, the most important GEBE system aspect is spoke durability. Then, it is maintaining minimum speed to keep the clutch engaged without slipping. I think a larger engine would not provide appreciable hill climbing improvement because the clutch will still slip climbing hills, although at a slightly lower rpm.

Ray