The E-cumbent - A project by Matt Shumaker

[recumpence]

Just got back from a 10 mile ride. That ride was a very hard ride for the bike. I did alot of accellerating up hills. At one point, I pulled 2,600 watts for nearly a minute accellerating up a very long hill. On top of that I did quite a bit of 35 to 40mph runs. Basically, I took the bike from one town to another (one of the reasons I built it to begin with).

The bike performed flawlessly. The only issue I have is the weight, or lack thereof. My bike is down around 45 pounds at this point. Also, it is a sharp handling bike. So, at 40mph it gets a bit sensitive to steering inputs. With more weight, some of that would be dampened out. Not that light weight is bad, but I find it ironic that the light weight drive is capable of speed that is in excess of what the bike is really able to handle well.

One thing that is weird about this is, the bike is so fast (top speed and accelleration), that I tend to treat it like a motorcycle. Then when I get home to charge it, I see that tiny motor and think to myself, "Wow, that little motor, tiny battery pack, and downright microscopic controller pushed me all that way at that speed?" Sheesh! When I find myself bumming about some minor detail with the bike, I need to stop and realize the performance I am getting out of 13 pounds of drive hardware.

Matt

 

[Ypedal]

Lol.. if you need to add weight.. just add batteries !!

Great to hear it runs good !!! would gearing it down even more to limit the top speed give it even more poke ? or does that just add more complex problems hehe..

 

[recumpence]

Oh, man, when it is geared down at 30mph top speed, the bike accellerates HARD. I am almost afraid to break something.

At this point, I have the clutch set to slip around 70 amps. That assures the ESC will survive and keeps my efficiency up.

Even in that hard running (with a little pedalling) I averaged 24wh per mile.

Matt

 

[lawsonuw]

The bike performed flawlessly. The only issue I have is the weight, or lack thereof. My bike is down around 45 pounds at this point. Also, it is a sharp handling bike. So, at 40mph it gets a bit sensitive to steering inputs. With more weight, some of that would be dampened out. Not that light weight is bad, but I find it ironic that the light weight drive is capable of speed that is in excess of what the bike is really able to handle well.

A heavy front rim should tame the twitches at speed. The extra angular momentum will act like a steering damper. Unless the twitches are due to your front fork flexing... then you're just doomed to be slow. :lol:

Anywho, good to hear the drive is running well. I might have to stop tinkering with through the gear drives and just throw power at the problem.

Marty

 

[recumpence]

The sensitivity is due to a very steep head tube angle. At 35mph or below, this thing handles fantastic. But, at 40, some decent concentration is required. :wink:

So, Marty, what part of Wisconsin are you in? I live about 20 minutes south of the illinois/Wisconsin border.

Matt

 

[AussieJester]

The sensitivity is due to a very steep head tube angle. At 35mph or below, this thing handles fantastic. But, at 40, some decent concentration is required. :wink:

Sounds to me like you need to get some rake/trail a happening Matt...chopper stylin' recumbent anyone ;-P...

 

[recumpence]

Part of me wants to go to a 20 inch rear wheel. That would relax the rake and improve the steering response (slow it down a touch) at high speed. But, that would also lean me back further and I do not want that. Besides, I love the handling as it is. It is only up above 35mph that the handling gets touchy. Below that speed it handles better than any bike I have owned.

AJ,

How's the E-chop-trike coming along? Haven't seen any eye candy on your thread in some time now.

C'mon, stop a'teasin. Give some joy! :wink:

Matt

 

[AussieJester]

AJ,

How's the E-chop-trike coming along? Haven't seen any eye candy on your thread in some time now.

C'mon, stop a'teasin. Give some joy! :wink:

Matt

LOl...i just uploaded a few pics then actually Matt, nothing major though shes just about ready for her initial tests before i pull her apart for prep/paint ...

Kim

 

[lawsonuw]

Part of me wants to go to a 20 inch rear wheel. That would relax the rake and improve the steering response (slow it down a touch) at high speed. But, that would also lean me back further and I do not want that. Besides, I love the handling as it is. It is only up above 35mph that the handling gets touchy. Below that speed it handles better than any bike I have owned.

Hm... it may also be lateral front fork/frame flex. Basically the front wheel makes a great gyroscope, and at speed any steering input causes an equal reaction torque on the front forks flexing the forks laterally. This effect goes both ways, i.e. as a flexed fork snaps back it will nudge the steering through the front wheel's gyroscopic action. Past a certain speed (depends on the specific bike etc...) this flex can develop into a nasty oscillation. Your recumbent might be getting close to this critical speed at 40mph. If this is the case a heavier front rim/tire/tube would make the problem worse! Another test is to quickly jerk the steering a little bit, you should feel a quick oscillation die out if the front wheel is flexing the frame.

Marty

 

[recumpence]

Nope, its rock solid. No oscillation at all. It is just very responsive at speed. Man, if it oscillated at that speed, I'd be toast.

Matt

 

[recumpence]

I took a couple snaps of the bike today for your viewing pleasure. :wink:

Oh, I found the "Perfect" (perfect for me, anyway) riding style and ideal human/electric hybrid ratio. Basically, I pedal like a madman on the flats and use the motor for the hills. Even if I crank the motor hard to accellerate and climb hills, I can average less than 12wh per mile assuming I pedal to my limit on the flats. So, I am looking at a good 25 miles on a charge that way. If I tone down the hard accelleration and just use the motor to get up hills without being crazy on the throttle, I could do 40miles easily.

I am looking to double my WH this winter. But, these lipo cells have more than doubled in price since I built this pack!

Also, this winter I am adding another digital display to display ambient temperature, motor temp, ESC temp, and front brake temp. (maybe motor RPM too). Beyond that, I am planning on making a new seat, adding a second front brake caliper, making new pedals, welding up a stylish/aerodynamic rear rack, and replacing a few goodies that have been wearing a bit.

Matt

 

[AussieJester]

Also, this winter I am adding another digital display to display ambient temperature, motor temp, ESC temp, and front brake temp. (maybe motor RPM too). Beyond that, I am planning on making a new seat, adding a second front brake caliper, making new pedals, welding up a stylish/aerodynamic rear rack, and replacing a few goodies that have been wearing a bit.

Matt

Looking forward to seeing the upgrades...have you decided on a digital display for the temperature sensing yet Matt if so 'link please' Would like to do the same purely for aesthetics LoL With regards to the 20in wheel you have thoughts of using, im no expert but wouldnt this equate to a much bumpier ride? Not to mention screwing with your gearing not you wouldnt rectify that obviously... Best of luck anywayz Matt truly the neatest 2 wheel electric recumbent floating about ...

 

[recumpence]

I use Eagle Tree systems E-logger V3 with digital display. It is $110US. That system logs all data that can be downloaded VIA USB. I primarily use it for the digital display. The display can be computer programmed by USB as well. It reads Amps, volts, MAH used, wattage, multiple RPM inputs, multiple temp inputs, GPS, speed, G-force, etc, etc, etc.

Yes, a 20 inch wheel would screw up my ratios. I will most likely stick with the 26 inch wheel.

This thing works so well, it seems strange to try improving it. But, anything can be improved upon. :wink:

Matt

 

[TPA]

That bike wins the award for most stealthy. From those angles you absolutely cannot tell it is powered.

People who see you on what looks like an ordinary bike doing 40 must go.....

 

[MitchJi]

Hi Matt,

I am looking to double my WH this winter. But, these lipo cells have more than doubled in price since I built this pack!
Matt

Unfortunately a more accurate description might be that the dollar haas fallen.

Also, this winter I am adding another digital display to display ambient temperature, motor temp, ESC temp, and front brake temp. (maybe motor RPM too). Beyond that, I am planning on making a new seat, adding a second front brake caliper, making new pedals, welding up a stylish/aerodynamic rear rack, and replacing a few goodies that have been wearing a bit.

I use Eagle Tree systems E-logger V3 with digital display. It is $110US. That system logs all data that can be downloaded VIA USB. I primarily use it for the digital display. The display can be computer programmed by USB as well. It reads Amps, volts, MAH used, wattage, multiple RPM inputs, multiple temp inputs, GPS, speed, G-force, etc, etc, etc.
Matt

Thanks for the information. I really like the idea of monitoring temperature.

 

[safe]

Nope, its rock solid. No oscillation at all. It is just very responsive at speed.

The under the legs front wheel design means the wheelbase is too short. If you were to still stay within the recumbent philosophy, but just go with the front wheel in front of the legs design you would be better off. Longer wheelbase designs tend to smooth out responsiveness.

Either that or switch to a road racer design. :wink:

My bike just starts to handle best at about 40 mph and at 50 mph it's just perfect. It's trying to park a bike like mine that is a source of troubles. (I use a custom bike stand)

Your wheelbase looks to be even shorter than most standard bicycles. My wheelbase is 52", what it yours?

A standard wheelbase for a bike is about 42-46" I think.

It's "okay" to have fast handling (steep steering head angle) but if it's also combined with a short wheelbase then that's a problem. Combine a long wheelbase and steep steering head angle and you get a bike that "carves" in a smooth arc, but it can be "set" into that arc quickly. It's a quick handling and yet smooth way to build a bike. (it's very good at higher speed, but not so good at slow speed)

When you start to add weight it introduces a lot of negative handling traits that sort of surprise you, so you are better off getting the handling right based on geometry first. (I would not recommend using weight as a way to resolve other geometry issues)

 

[johnrobholmes]

There are also fewer people importing 10C cells, so there is less competition.


I have hit up a few factories to see what kind of production we would need to get a batch made. I betcha I could get rid of 500 10 amp hour cells in a hurry. The price of LiFe is pretty ridiculous for the power IMO. Up for 12 more cells Matt?

 

[Jeremy Harris]

Safe,

Although a longer wheelbase tends to give some directional stability, the most likely cause of the effect Matt experiences is due to the lower C of G and the consequent reduction in reverse pendulum stability. I notice pretty much the same effect on my USS SWB 'bent going down hills at speed.

LWB OSS 'bents (like the one you've illustrated) tend to have a higher seat and a more upright riding position, so will have a higher C of G than Matt's OSS Action Bent.

Although it seems counter intuitive, a high rider C of G does give additional stability. If you've ever tried to ride a Pennyfarthing, then you'd have noticed that it's actually pretty stable, even at low speeds, in part due to the high C of G.

Jeremy

 

[recumpence]

There are also fewer people importing 10C cells, so there is less competition.


I have hit up a few factories to see what kind of production we would need to get a batch made. I betcha I could get rid of 500 10 amp hour cells in a hurry. The price of LiFe is pretty ridiculous for the power IMO. Up for 12 more cells Matt?

I would love 12 more cells, if I could get them reasonably. I paid $435 for mine. It would cost $1200 now!

Matt

 

[johnrobholmes]

HOly Crap!! That is plain ridiculous. I just checked the MA site and you are indeed not bluffing!


Single 10ah cells shouldn't be anywhere near $100 each. $25 each retail is more like it, especially for china made cells.

 

[recumpence]

HOly Crap!! That is plain ridiculous. I just checked the MA site and you are indeed not bluffing!


Single 10ah cells shouldn't be anywhere near $100 each. $25 each retail is more like it, especially for china made cells.

No doubt! Every time I check the price is drastically higher. It is like watching the price of gas or airline tickets.

Safe,

My bike is in no way unsafe to operate. It exibits no ill handling what-so-ever. However, it is definately letting me know 40mph is enough. Basically it is like the first time I drove a friend's supercharged AMC Benz. That car is fast and very responsive. If you look into the other lane, the car follows. It is very willing to change direction. That is kind of what my bike is like. It is so extremely willing to change lanes (lines), that at high speed, more concentration is required.

I do not want to change the handling of the bike at all, though. For one thing, this is the only recumbent I have ever ridden that is not a handlful below 7mph. Typically, a low recumbent requires high speed to be stable (stay upright). Not this bike. It is easy to ride slow or fast. But, at high speed, a bit more concentration is required. :wink:

John, wait till you see my mountain bike setup I am planning this winter. Fantastic!

Oh, True RC is another discount lipo source. They are located less than an hour form my house. I will be calling them soon about some cells. They only go up to 5ah cells, though. So, some series/parallel majic will have to happen. But, I think I could get twice the AH per dollar through them.

Matt

 

[johnrobholmes]

I have contacted TrueRC with no luck so far. I don't like the idea of too many parallel cells, but we gotta work with what is available.



Can't wait to see what you bring together for a mountain bike!

 

[recumpence]

I have talked with them at length when I was building my bike. Good people.

I do not mind parallel cells. They stay in ballance that way. Too many series cells go out of ballance.

Actually, it is kind of nice having multiple cells because you can setup separate small packs to fit where you want.

Matt

 

[johnrobholmes]

I was thinking 6 cell series bricks would be nice. For a more standard voltage jump 3 cell bricks could be used too.


Lots of testing to be done with pack layout, for sure. I dislike too many parallel cells because it just adds in more cells to fail. 12ssp vs 12s1p of the same capacity has more wiring, more soldering, and more seals to go bad.

 

[recumpence]

My mountain bike project may recieve a hand-me-down from my recumbent in the form of my 10Ah lipo pack. It is two separate 6S packs in series. That pack will be perfect for it. Then I could move to True RC cells and do something along the lines of 48 volt 20Ah for long distance riding.

My mountain bike will be setup for mild top speed (around 20mph) with HUGE torque. I am looking at around 4,000 watts. So, with that much power on tap with 20mph gearing, the bike should snap wheelie like a dirtbike.

What I would like out of that bike is a power house, light trail riding, sometimes trials, and occasional around town fun bike. Even if I got only 30WH per mile with hard riding, that is still 10+ miles of smiling between charges.

At any rate, that bike will probably be my gearbox test mule (although I will definately send out a few to customers to test first).

Matt