33cc Gas/Electric hybrid bicycle project

The plan is to build a legal hybrid bicycle that uses a 250w motor (which is the legal limit here in Norway) for propelling the bike forwards and a lightweight generator for charging the battery while driving. The bike must have a speed limited to 25kmh and a pedaling sensor, i want to hook up the sensor to a hidden switch so that i can turn it off and run on only the motor. I hate the idea of having to stop to recharge the battery for hours, i want to be able to ride for as long as i have gasoline! I want to legally be able to ride anywhere and everywhere to boast my urban exploration experience, and also for daily commuting 8)

The reason i'm making a post on this is that i need advice and direction of someone who is experienced with electronics. As my knowledge on that particular field is quite limited. As for now anyways...
And perhaps, if i am successful at this project this can help others do the same. I will post pictures along as i progress.

For the build i will use a lady bicycle as it has more space for the motor and dynamo. (Don't worry, it definitively wont look like a ladies bicycle when i'm done with it) :wink: The first thing i will do is to sand blast the old rusty frame and bicycle parts (I get to do this for free) and then weld on the mounting brackets for the engine and dynamo. I have an almost unlimited supply of old bikes and rusty parts as i live next to a scrap yard. That's also where i found the engine i will be using to drive the dynamo. The engine is an almost unused German two stroke Sachs Stamo 30 from the 1960's, it even has a pulley wheel at the perfect location for a belt drive to the dynamo. The engine is really small, but also very robust, i have reason to believe it will keep on going forever with good maintenance. It weights a total of 4kg, and is able to spin at 7500rpm. If you go to 1:10 in this video you can hear how fast this thing is. Sounds like a jet engine! [youtube]https://www.youtube.com/watch?v=APdbBmY7Bcg[/youtube]

As for the electric motor I've decided to go for a front mounted hub motor. I'm still not certain of which brand to go with yet. I want a hub motor that will never fail or overheat! I have thought of purchasing a Bafang 250w and getting someone to machine steel planetary gears for me (Noise from the gears is not a concern). Then i will either air cool the hub motor or fill it with oil and mount a neodynium magnet somewhere close to the planetary gear to keep tiny metal shaving away from the magnetos in the engine. Perhaps its better to make the gears out of aluminium, brass or titanium if i can afford it. Then shavings sticking to the magnetos in the motor wont be a concern. The oil filling is pretty self explanatory but i have created a sketch of the air cool setup. The "rods" are hollow with a 90° bend at the end to prevent water from dripping on top of the coils in the engine in case of rain. If any water gets inside it will drip out the rods facing downwards. The rods and the mounting holes will be threaded and secured with super glue. When the tire spins the air will be thrown out of the rods and fresh air sucked in to the intake holes, similar to an impeller. Creating this will take a lot more effort than to simply seal the motor off and filling it with oil. Which idea is the best if longevity is my goal?

I would also like a battery that is as small and light as possible. It doesn't really need to hold a lot of charge as the generator generates constant power. Do i even need a battery? Could i mount some kind of regulator to the dynamo to keep the voltage and watts to the specifications of the hub motor?

Here are some specifications of the Sachs ST 30 engine,

Power:
1.5 hp / 1.1 kW at 6,500 rev / min
1.7 hp / 1.3 kW at 7,000 r / min

Operating speed:
(4.000 **) 5000-7500 U / min

Torque:
0.22 kpm at 4,500 rev / min

I would appreciate if someone could help me find a suitable dynamo that would work well with this motor. The dynamo must also have a pulley wheel on it. I'm not exactly sure how fast the pulley wheel on the motor spins as it has a small gearbox. The reduction ratio here is according to the manual either 3.0 or 3.7, i'm not sure exactly which one

Also check out the sketches i made!

This is a very bad idea, 250W motor is not nearly enough power. The bike will weigh too much.

You will get much better efficiency by running the bike directly from the 33cc motor, instead of trying to change a battery.

Gas powered bicycles are not allowed here in Norway

However, a gas powered generator hooked up to an electric motor is the only exception! Only then the bike will still be considered an electric bike

Perhaps overvolting the 250w motor could give me enough power?

I just don't think you will be happy with the end result.

How much does the 33cc generator plus gas weigh, I'd invest that weight in more batteries if you need more range.

Is that first sketch supposed to be the hub motor? That also will not work, you have drilled where there are magnets.

el_walto said:

I just don't think you will be happy with the end result.

How much does the 33cc generator plus gas weigh, I'd invest that weight in more batteries if you need more range.

Is that first sketch supposed to be the hub motor? That also will not work, you have drilled where there are magnets.

Click to expand...

The magnets are enclosed in another casing on the inside of the Bafang motor. Drilling in the outer case will not have any effect on the magnets or coils

The motor it self weights 4 kgs, it can hold 1 litres of fuel, and i guess the dynamo weighs 3kgs and the welded on engine mount around 2 kgs or less. That adds up to approximately 10kgs in total

http://zuki.net/picslive/motor-open-45.JPG

I think your overdoing it. I believe removing the 33cc engine and replacing with added battery is the way to go. For one, you remove the sound of the engine and get a nice quiet ride.

How far do you have to travel. Erm, maybe say this another way, how far do you want to travel? How fast do you want to travel is another question as you may need to break the rules here on your 250w limit. Being from a place that is already familiar with the electric assist, I'm assuming you've ridden a bike with assist? You want faster? Break the rule, get a bigger motor.

250w isn't something to laugh at as long as your not burdened with cargo weight. It will go far with the right battery configuration, and you will make it go far as long as you give a little with it.

OK, maybe I'm being too negative.

Why are you planning on not using the original spokes? I'd think they would be more reliable than drilling the motor like that. You can't thread pipes into the motor shell, it is not thick enough.

I think you should build the 250Watt ebike portion first, see how that works, then consider adding the generator wackiness afterwards.

el_walto said:

OK, maybe I'm being too negative.

Why are you planning on not using the original spokes? I'd think they would be more reliable than drilling the motor like that.

I think you should build the 200Watt ebike portion first, see how that works, then add the generator wackiness afterwards.

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No problem, i am all ears. Please don't confuse the venting tubes with spokes. As you can see these are placed in the middle of the hub motor. I just haven't taken the effort to draw up all the spokes in the sketch. They will still be attached to their original holes Its simply a theoretical sketch. I may also go with the oil filled hub, if you read the entire original post.

I want to plan ahead before investing in ebike parts. Making sure things will work their intended way and ensuring longevity.

The intake holes will make your idea of oil cooling null and void as it will seep out.

I like your profile pic.

Run your motor without the modifications with the chores you have in mind. Need to haul the 200kg of chicken feed from the store to the barn, try it unmodified. Put your hand on the motor, too hot to touch after a few seconds? Only then try a modification. As far as durability, if you run the motor like they are intended, as in, not pushing too many watts, you should be getting quite a bit of usage out of them.

melodious said:

The intake holes will make your idea of oil cooling null and void as it will seep out.

I like your profile pic.

Run your motor without the modifications with the chores you have in mind. Need to haul the 200kg of chicken feed from the store to the barn, try it unmodified. Put your hand on the motor, too hot to touch after a few seconds? Only then try a modification. As far as durability, if you run the motor like they are intended, as in, not pushing too many watts, you should be getting quite a bit of usage out of them.

Click to expand...

I think you should read the entire post before making a statement. "i will either air cool the hub motor or fill it with oil" That does not mean i will do both, of course i know that you cannot fill an engine that has holes with oil.

The engine can be lukewarm on the outside while on the inside the coils could be so hot the insulation gets burned and currents passes trough! If you knew how a geared hub motor is working in particular you would be able to understand, and if you don't, please do your research first. I feel it really shouldn't be necessary to explain this... :lol:

I don't know much about the generator configuration, but most 250w systems will run 24-36v.

You should start by ordering yourself the ebike kit. If you are going to charge all the time maybe get a small cheap battery as a buffer, maybe two or three 12v 7ah SLA bricks?

Have you ridden a 250watt hub motor? They are not very powerful.

I'm going to differ and say its a good idea, if you can make it work! That's a bit of an if right now. Its a good idea because that's the basic concept of the Chevy Volt - an electric/gas hybrid which uses hub motors and the sole function of the gas engine is as a generator. That's a really big project from a really big company and the principal is sound.

I believe you should focus on matching the hub motor to the generator. Rather just assemble some random parts, because you have them, or sound good to you, really work out the matching factors. In my estimation, the generator should be about 110% of the amperage of the hub motor. An added 10% to account for dis-efficiency in the transfer of power. So when the generator is on, its producing all the amps needed by the hub motor. The battery serves as a keel and also is there for the draw during throttle from zero to speed.

You have chosen a 250 watt hub motor to be street legal. What a number of folks do in a similar circumstance is to get a larger hub motor and have a current limiting controller. So when on the streets, its switched to be street legal and when not, switched to deliver higher power. What most folks don't realize until its too late is that 250 watts is not much and certainly not enough to deliver torque when needed, like going up hills. Since you're investing, I'd get a 750 watt hub motor that can deliver high torque, a direct-drive brushless motor, the technology for which is much improved. You may want to look at the Heinzmann PRA-180 among others. Then once selected, invest in looking at and then buying or building a controller. FYI, there are controllers on the market that have built in circuitry for the charge cycle as well as the discharge. One of those.

Then I'd build out the eBike without the generator. It'll be wholly functional. With it all, I'd measure the amperage draw, min, max and normative continuous, so you have an actual amperage profile of your bike. Then and only then, would I add in the gas fired generator. Again, I'd size it exactly, rather than by guess work.

Finally, once you've completed your project and its work, and this is important, post back your experience, your problems, solutions, things that worked or didn't, so others can benefit. And throughout, be open to constructive criticism, but don't take in any nay-sayings, unless its from someone who tried and failed - those you can learn from. Best of luck with your project!

I like the project I have 4 things to say about it:

- get a modern electronic ignition for the old Stamo motor if you use it. The one that is on my 1970s Stamo 282 is a pain in the ass. You won´t regret it.

- Have you driven a front motor? I found it really awkward and would never install a front motor. Maybe you could use the geared rear hub motor from the croatian guys at Zelena Vozilla. Look for their catalog it even has steel planetary gears. It is for 750W rated and costs 100$ AFAIK.

- You should consider that the european law says 250W constant power. I personally would try to get a motor and electronic devices that can handle a lot of burst power and run like 1kw burst power for acceleration than you can cruise at 25km/h wich won´t need much energy anyway. Just put a 250W sticker on motor and controller and make sure your bike is not faster than 27km/h and does not put out more than 250W constantly.

- (Maybe you can run a 3 phase generator directly to the 3 phase motor without using a controller and a battery. That way you would regulate you speed over the ICE engine with a accelerator.)

just realized not that easy unless you would have 3 eletric switches that would connect generator and motor after pushing a button and checking if you pedal. That way you could start your ICE and dissipate the eletric energy into ressistors and connect the generator to the motor when you want. Might be diffucult with the law in this configuration

there was a mini coverted to electric here in the uk back in around 1997 that had a electric only range of around 100miles but it also had a 250cc petrol genny in the boot and was only used as a range extender ( upto 350miles ) so it do work , I would use a small outrunner as a genny but re-wound for a much lower kv and power value value , and I would also not use such a big ice engine, as i dont think it would be needed on a e-bicycle

I don´t know about using another motor. Stamo stands for Stationärmotor -> stationary engine they are reliable and up to the task of running at a constant rotation for cruising. They might also have some regulating mechanical device to keep the revolution constant when more power is demanded at least stationary engines often have it.

Less weight is of course important and would improve the handling especially if you place the motor as high as in your drawing.

if the genny is used as a range extender then the load will be ( more or less ) constant on the ice , so no issues there, also the ice will not need to be running all the time i.e if regen enabled, coasting, pedalling or soc not low enough all controlled with electronics., you will have to work out a way to start the engine on demand without no messing about but should be easy enough.

- Arkmundi

I'm glad you think it's doable.

You're right, purchasing the hub motor and an electrical system first before i start making the engine mount for the generator and dynamo is the safest way to go to ensure that everything is compatible. I think that i'll be the way i will do it. Do you know if there are batteries that are very small and lightweight that doesn't hold much charge but produces enough watts for the motor? I don't really need all that much storage capacity.

And yeah, a Heinzmann hub motor would be THE ultimate motor for the project. They seem extremely robust and well made. However, as with mostly everything that is high end it's also expensive. At the moment i cannot afford such a motor and system. In half a year - maybe. They seem to be quite rare too. Perhaps i could buy a second hand Heinzmann as long as it doesn't have corrosion on the inside or burned coils?

Getting a larger motor sounds like a good idea as long as it complies to the law. If the bike would just be a normal ebike i wouldnt be that concerned of breaking the law. But having a noisy 7k rpm screamer mounted to it is sure to draw a lot of attention, especially as i live in the city. It is only a matter of time before i get stopped by the police for control and when i do i want it all to be legal. I have sent an email to the authorities to make sure that its legal, they sure take their time answering, i sent the email two weeks ago and haven't heard anything from them yet.


- sigimem

Converting to electronic ignition sounds like a good idea in the long run. Before i do that i must first convert my newly restored Jawa/Cz motorcycle to electronic, or may even digital ignition with a brushless dynamo! I guess i will have to live with the points and condensers for now at least. Adjusting every now and then not that much of a big deal for me anyways, at least not on a bicycle! :wink:

The old bicycle that i want to use for the project has no gear cassette on the rear wheel. Seems to me like all rear hub motors are designed for modern bicycles with a cassette sprockets, maybe i am wrong? The reason i like front mounted hub motors is that its easier to remove for servicing and cleaning without having to deal with the chain and so on. I have never actually ridden an ebike before so i really don't know what the difference in handling is.

I am also wondering, how can i restrict the maximum speed? Sorry if that's considered a dumb question around here. I don't have much experience with electronics, or ebikes.

I will try to mount the Sachs motor as low as possible. Perhaps having the dynamo above the motor, opposite to whats shown in the drawing.


- gwhy!

I like idea of having a smaller battery and a constantly running motor more. Then i wouldn't have to deal with power loss over time as the battery drains, or the problem with starting the engine often. A solution to starting the engine on the fly could perhaps be to use the dynamo as a starter motor. Some car dynamos are used both as dynamos and starters. Perhaps i could just flip a switch and direct the power from the controller to the dynamo instead of the hub motor and then switch back once the engine runs again?



Thanks for all the answers and ideas!!

I have attached a picture of a similar project i had. It was more of a weekend project as i had found a chainsaw motor and an old suitable bike. Sadly it did not work, the gearing ratio was way to high so the clutch overheated and got stuck

Most hub motors have a thread on one side you can either fit a casette or a single sprocet with a freewheel that can be choosen so choose the one right for your chain.
Someone in this forum has a signature it says(among other things): Rear hubs are always best. That´s true in my opinion

Speed is restricted by the maximum voltage you motor gets (mostly) from the controller. A indicator for the speed at a Voltage is the kv you should read it up. Torque depends on your current so how many Amps you will feed to the motor. You can restrict both over the controller and the Cycle Analyst (CA read this up as well).

I think you might start with the motor what voltage does it need to run 25km/h is it a brushless dc motor 3 phase wires or a brushed dc motor with 2 wires to it. Then think about your solution for a throttle and controller. Now you can go on to your generator what voltage how much losses how fast should it spin ?

How far do you want to travel?

250km a day? At 25km/h average that's 10 hours on the saddle and your butt will be the limiting factor here.

250km is doable with a nice battery pack. 1kWh can do that at 25-29km/h, if you add significant amount od pedaling. It weights just 4kg if built from high energy 18650 cells...

The 250W law in Europe is only for continuous power which lacks any clear definition. A 48V BionX system will consume more than 1300W peak power from its battery and it is perfectly legal in Europe...

Put a mini wind turbine on the front and charge from that do not go over the handle bars tho!!!

Oh, come on! The question is, can a mini-volt like eBike be made, for unlimited range on the road. I believe it may be accomplished, not that its necessarily, until proven, a "good" idea. Anyone considering long distance eBike travel must account for "re-fueling" whether by plugging in a charger or as suggested, using conventional gasoline to run a generator. I myself have considered these options, for the same reason - long distance travel. Elon Musk's solution for the Tesla is solar recharging stations everywhere, so a vehicle is always in range of one. So there are genius types trying to work it out. There are cities currently implementing public access recharging stations because for a city, lots of eBikes is a much more sane approach then a bunch of ICErs.

Zone Seeker said:

- Arkmundi

I like idea of having a smaller battery and a constantly running motor more. Then i wouldn't have to deal with power loss over time as the battery drains, or the problem with starting the engine often. A solution to starting the engine on the fly could perhaps be to use the dynamo as a starter motor. Some car dynamos are used both as dynamos and starters. Perhaps i could just flip a switch and direct the power from the controller to the dynamo instead of the hub motor and then switch back once the engine runs again?
:

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Get two/three(24v-36v) 12V 7Ah SLA batteries. You really don't need much battery if you are running a generator all the time. And 250watts is not hard on a small battery. Or consider two/three(24v/36V) 12V 12Ah batteries if you are going to run without the generator for longer than a couple minutes.

Please see the ebikes.ca simulator here: http://www.ebikes.ca/tools/simulator.html

el_walto said:

Zone Seeker said:

- Arkmundi

I like idea of having a smaller battery and a constantly running motor more. Then i wouldn't have to deal with power loss over time as the battery drains, or the problem with starting the engine often. A solution to starting the engine on the fly could perhaps be to use the dynamo as a starter motor. Some car dynamos are used both as dynamos and starters. Perhaps i could just flip a switch and direct the power from the controller to the dynamo instead of the hub motor and then switch back once the engine runs again?
:

Click to expand...

Get two/three(24v-36v) 12V 7Ah SLA batteries. You really don't need much battery if you are running a generator all the time. And 250watts is not hard on a small battery. Or consider two/three(24v/36V) 12V 12Ah batteries if you are going to run without the generator for longer than a couple minutes.

Click to expand...

Lightweight and inexpensive, exactly what i need. Thanks for the tip!

I talked to the people who know all the rules about these things. They told me that having the generator mounted on the bike makes it a hybrid vehicle that must according to the law be registered. However, they told me that if i build the generator on to a trailer and mount that to the bike it would still be considered an ebike. So the plan is now to build a small bicycle trailer with one single wheel and an old axle that i will weld to the frame of my smal trailer that will serve as the joint connection. I will get back to that later and make a sketch... And add some pictures of the bike i will use aswell, now i can ditch that ladies bike and use this nice beach bike frame i found!! 8)

This is the frame i will be using. May look a bit rusty now but after the sand blast and repaint it will look like new! Still not sure about the color though. Perhaps two tone red and cream white. Or.. Steam punk-ish black with metallic gold details.