600w, 900w, 24v, 36v motor. Not sure which is best

Will Snow

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I am putting together a electric recumbent trike that will have gear selection to the drive wheel.

I will be using SLA batteries for now so weight is something I need to think about.

Here is what I am interested in doing: top speed of 20-25 mph and pretty good range for around town, maybe 20 miles with very limited peddling and mostly level terrain. I thought for longer trips I could add a trailer carring batteries connected to the main system and may installing a switch easy to reach to activate these trailer batteries.

So far my thoughts have been a 600w or 900w 24v motor or moving up to 36v. I have been looking at motors that may fit between peddle cranks which I need for this application.

Somewhere along the line I think I was warned that a higher powered motor is not good at slower speeds, say, 7-10 mph. So that is something I don't know about. I don't want the bike to be a wimp, but also don't want to go into "overkill".

I have been leaning toward the 600w 24v approach, thinking the gearing will be a big help for performance and I could carry more batterie for more range than with 36v. As you can tell, I am not sure about the best way to do this.

I already got some good help on this forum from Professor and Johnrobholmes regarding another part of this project. So, thought I would try again with these questions.
 
Well, from my reading I have concluded that probably the best match of power and performance is in a 36v system, for bicycle uses. Since you are looking at SLA batteries and a tadpole recumbent, I'd suggest you consider a main rail motor mounting point under the seat, with a chain loop forward to an inside secondary crank sprocket so as to feed the power directly through the pedal power system and utilize the gearing. Depending on what recumbent you are using, there may be room under/behind the seat to place 3 series connected high amp hour motorcycle batteries. The battery trailer idea has merit.

My recollection is that CA limits e-bikes to one shaft horsepower, which is (approx) 750 watts, so a 600 watt motor will be legal. However, are there CA restrictions on "transmissions" for e-bikes? Any multiple gearing shifter system is a transmission.
 
Trike

The trike is a Terra. I know California has some restrictions: 20 mph speed limit for electric, peddles, etc. and I believe I read 1000w is the limit. Think you are probably right about the transmission. So far, in the 29 years I have been tinkering with and riding motorized bicycles an officer has never questioned me about it, except one time at a police station and that was more out of interest in it. But there could always be s first.

36v, Well, behind the seat there maybe room. 900w 36v, wonder how that would do? I'll recheck California law, pretty sure it is 1000 watts.

The last bike I put together was a Tour Easy recumbent with the motor under the seat and running a chain to the main sprocket as you suggested, which turned out very well. This time I want to have a shorter chain from motor to sprocket if I can mount it neatly.
 
California law

Just reviewed the California DMV handbook under motorized bicycles,section 406A & 406B. 406B is for electric bicycles.

Up tp 1000 watts is legal, but no more than 20 mph

No mention is made of a tranmission so it looks like I am ok using gears.
 
Sounds good. It gets a bit pricey, but with the forward boom design the Terra Trike uses, it would work to use a motor from high end RC technology, such as an outrunner, and a custom fabbed gear reduction system. Look up the work log and posts by recompence, here - he did a truly outstanding piece of design and fab work for his recumbent. Another consideration might be to go with a pair of 500W wheelmotors as your front power and simply forego gearing - leaving the rear wheel powered by the pedal system.

I am actually working on a design for a tadpole velomobile using just that - two powered front wheels and a pedal driven rear. Louisiana law says a powered trike must have a roll cage, so if I have to go that route I might as well make it a velomobile.
 
Wheel motors, is that hub motors?

RC motors, I saw his video and you are right, that trike really goes. I remember the RC motor application but not sure what they are.

The trike is still being shipped, after it gets here I'll be able to take a closer look being this is my first trike. still working it out. Motor under the seat, motor up front, wheel motors ???, will have to learn more and think about it for awhile.

Velomobile, now that's interesting. What kind of body are you making? Hope we can see some pictures of it later.
 
On the velomobile design, I am looking at resinated stretch fabric as being the lightest skin I could make. A basic bullet body with the front wheels outboard of the cabin, and a lucite type windscreen, open top. As I work the design up I may post some sketches, if I get to build it there will be pics.
 
Velomobile

A covering that I know of that I thought would work good is stits ( I may have spelled that wrong) It's a covering we used on older fabric aircraft. It's good to work with, strong and will last for years if painted to proctect from UV. One plane had never been hangered and still checked in the green after 20 years. A special glue is used to attach it to the frame. When dry any wrinkle can easly be ironed out. It comes in standard and light weight material.
 
I will be using SLA batteries for now so weight is something I need to think about.

Here is what I am interested in doing: top speed of 20-25 mph and pretty good range for around town, maybe 20 miles with very limited peddling and mostly level terrain. I thought for longer trips I could add a trailer carring batteries connected to the main system and may installing a switch easy to reach to activate these trailer batteries.

Not sure a trailer with more SLA's will do you any good for distance. (depends how many batteries your going to put on the trailer)
You will have more amps, but look at the extra weight you have to pull (trailer and batteries)
A 12 Volt 12 Amp weighs about 10lbs, a 12v 18ah weighs 14lbs

there may be room under/behind the seat to place 3 series connected high amp hour motorcycle batteries.

Motorcycle batteries wouldn't last more then a few runs (if your lucky)
they are not meant to be fully discharged, they are made to start a motor only, (just as car batteries, they are not deep cycle)
You need to use deep cycle batteries.

Even thou a motorcycle battery or a UPS system battery raated 12v 12ah they are not the same as a 12v 12ah scooter battery.

Oh, I would also go with the 36v (as SimpleSimon suggested) over the 24v anytime.
 
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36v

I understand about the deepcycle and the 36v battery. I have been on a forum that is all electric and 36v and up is what they suggest. Several recommend 48v, I really don't want to go with that many volts. Some suggest higher power motors and other tell me they will drain too much power to get a good range. With what I am learning my thoughts so far are 36v as suggested and 600w motor. Many feel the hub motor is a good way to go and it probably is. I am still leaning toward using the chain drive as described by Simple Simon so I have some selection over gearing. In my area that is mostly flat, gearing is probably not that important and the hub motor may be a better choice. I am still going to give it some thought, just not sure yet.
 
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