Safe's Electric Bike Project #001

[safe]

Okay Xyster.... now I know you have about 2-3 times the horsepower that my bike does, but what is the TOP speed downhill or otherwise that you have actually achieved?

Do I have you beat at 47 mph?

(there are Gravity Bikes that have done 50 mph if the hill is steep enough)

 

[Lowell]

My downhill speed isn't much different from flat ground... it's hard to push all that air around at 45mph.

 

[xyster]

In order to prevent Xyster from "spamming" my threads with solicitations for me to look at this circuit I've come here to offer my blessings and to confirm that I've seen it.

Sheez, some people have no appreciation for what others try to do for them! :?

Okay Xyster.... now I know you have about 2-3 times the horsepower that my bike does, but what is the TOP speed downhill or otherwise that you have actually achieved?

38 mph up an ~2% grade. I don't trust the bike to remain stable and in-one-piece at speeds any higher.

Do I have you beat at 47 mph?

Depends, how fast have you gone up a hill?

 

[safe]

My downhill speed isn't much different from flat ground... it's hard to push all that air around at 45mph.

My flat land speed is about 40 mph, so I only gain about 7 mph on a hill, but I've got gears so there's little power, but I'm not FIGHTING against the back EMF current in the motor. Anything fixed gear will be fighting itself if you try to exceed the no load speed. Mine freewheels too, so the motor becomes disconnected. (on my old gearing there were many times when on a steep hill the bike was going faster than the motor could keep up and it would freewheel)

 

[safe]

Depends, how fast have you gone up a hill?

I should have bought a "Hemi".

So I've got you beat on top speed, but not on power...

 

[Lowell]

My downhill speed isn't much different from flat ground... it's hard to push all that air around at 45mph.

My flat land speed is about 40 mph, so I only gain about 7 mph on a hill, but I've got gears so there's little power, but I'm not FIGHTING against the back EMF current in the motor. Anything fixed gear will be fighting itself if you try to exceed the no load speed. Mine freewheels too, so the motor becomes disconnected. (on my old gearing there were many times when on a steep hill the bike was going faster than the motor could keep up and it would freewheel)

My no load speed is somewhere above 100km/h, so that's not an issue. I'm not going to mess with the speed controller this time so any more speed right now will come from minimizing losses, both electrical and aerodynamic. If I haven't broken 50mph by the time my new MOSFETs arrive, amping up to 50 or 60 amps should do the trick nicely.

Justin at Ebikes.ca was mentioning soldering copper braid on to the FET busses, which is something I'll do to the blown up controller at the same time.

 

[safe]

My actual no load speed is 56 mph, but before you even get there the power is dropping off very fast so if you actually want to GET to your peak speed based on "peak power" you need to gear the bike higher. (or in your case you need to have the voltage higher)

For example:

For me to achieve my "ideal speed" (maximum speed that can be achieved at peak power) I would need to gear my bike so that the no load speed would be about 64 mph. That's a full 8 mph above where I am now.

So you always have to "over shoot" the mark in order to hit it...

But also you need to think more about aerodynamics. Since aerodynamics is XXX rated (drag increases as the cube of X speed) you might be having more troubles with power getting there. For me I can achieve 42+ mph with only a little over 1000 Watts of power. On a regular mountain bike it might take 2500 Watts to do the same thing. So you have to view aerodynamics as your main obstacle to gaining more speed. Of course, brute force will do it, but your range will go down as a result...

 

[Lowell]

The Ebikes.ca simulator says peak power speed at 72v is around 95km/h. I'm running 84v, so that should put it around 110km/h. With some aero work, there's much more potential in my setup as it will gain power the faster I go.

 

[safe]

With some aero work, there's much more potential in my setup as it will gain power the faster I go.

What is your calculated "peak power" (Watts) and at what speed does it occur?

You have to plot power verses speed because at some point those two curves intersect. It's at the point of intersection (based on wind resistance) that you get your "actual" top speed.

Without the wind resistance being plotted against your power you can get some very unrealistic numbers.

I've already got the 5304 setup on a spreadsheet at 72 Volts and 35 Amps and the numbers I get are:

Peak Power - 1970 Watts
Speed at Peak Power - 44.1 mph
Top Speed With A VERY Streamlined Bike (like mine) - 48.8 mph
No Load Speed - 54.2 mph
Wheel Size - 26"

Feel free to download it...

 

[Toorbough ULL-Zeveigh]

Ho-kay, I naturally assumed that this thread was about speed record on level ground. If you're now including downhill, then you need to get in touch with this man who also happens to be a member here at ES.

http://groups.google.com/group/Tida...89c35/d1b7a80b8582418e?tvc=2#d1b7a80b8582418e

Kirby Hill tonight, Uma let loose like nobody's bidness and set me
flying at 63.1 mph!


(Uma is his pet name for his TFSx).


I'm guessing 68 mph or so might be possible from the top of
Kirby Hill with no regen but won't be trying that till I get a better
front fork and wheel.


Believe it or not I hit very close to 50 mph in REGEN yesterday before
I pinned the throttle about 200'-300' from the bottom. This hill is SO
steep at the top (and with a bit of a twist to the left that prevents
you from seeing the bottom for quite a while) that I normally brake a
bit in conjunction with REGEN until about 1/3-1/2 way down (I think the
entire hill is about .2 miles long). But yesterday I felt comfortable
enough (from doing the hill so much lately) not to brake at all at the
top and to just let REGEN engage on its own and see how fast the bike
would go in REGEN before that point where I feel safe visibility-wise
to let'er rip.


Larry




And in case you really are talking on the level there's always this half decade old hub design. I'm guessing you've already seen it since you're shooting for 1 mph over. Not bad for a direct drive hub tho, huh? Remember, I'm just a messenger, so don't hate me.

http://www.greenspeed.us/tidalforce_electric_motor.htm

Check out this WaveCrest electric velodrome pace bike - this yellow speed demon whips around insanely banked turns at speeds of up to 45 mph. It has a light-weight Cannondale frame and racing rims specially configured to meet the speed and range requirements of the recent 2005 UCI Track Cycling World Championships in Carson, California.

 

[knightmb]

Feel free to download it...

I tried the spreadsheet, it won't open in Open Office or Microsoft Office, both say it's corrupt?

 

[safe]

I tried the spreadsheet, it won't open in Open Office or Microsoft Office, both say it's corrupt?

Try renaming is as a "*.wks" file. It was created in Microsoft Works, so that's probably what's causing the problem.

It's not dangerous... it was made on Windows 98... so it's old stuff...

My Windows XP motherboard died on me about a year ago, so I've been using my old machine for all this time... one of these days I'll get a new one...

 

[xyster]

Feel free to download it...

Safe, I downloaded your spreadsheet, but like knightmb, it doesn't open for me. I tried renaming it like you said -- no difference. When forced to open it, excel shows it as garbled junk. Can you export this as an .xls please?

 

[knightmb]

The format may be too old. I can't get it to open in Excel or Open Office when I rename it to a *.wks file

 

[TylerDurden]

I converted it to xls.. Open Office & excel should now open it

 

[xyster]

Hey, it opens now! Thanks, TD.
But there doesn't appear to be any graphs with it. Do I need to roll my own graphs?

 

[safe]

You're going to have to reselect the columns to create the graphs.

Here's that same file after I converted it to (true) Excel format. No graphs in it now though...

 

[safe]

In case anyone is interested in multiple speed bikes, here's my MY1020Z3 "Geardown" motor pumped up to 48 Volts and I'm using this newer format with the rows and columns reversed... so just when you learn the last one I flip it on you. In many ways this newer format is easier to read...

 

[safe]

50 mph on a Downhill Achieved (2/22/07)

I managed to get the bike up to 50 mph for about 6 seconds on a downhill today.

 

[Matt Gruber]

Good for you!
How many shifts did you make?

 

[safe]

How many shifts did you make?

It took all six gears to pull it off. Without the ability to shift I wouldn't have built up the momentum to get to top speed... gears work... my little 750 Watt motor powered bike is the evidence. Sixth gear was engaged just as I got into the highest speed section and it could pull it for only 6 seconds before the hill flattened out. In Missouri a 100 foot high "hill" is about all that you can get. (imagine if I lived in Colorado)

 

[Matt Gruber]

so it went 46 in 1 gear?
and it took 6 to get 50?

 

[safe]

so it went 46 in 1 gear?
and it took 6 to get 50?

What are you talking about?

My bike has always had a 6 speed derailler gear setup in the back. I have the choice of a 22 tooth or a 14 tooth for the front gear. The rear "freewheel" is 14, 16, 19, 21, 25, 28. (I think)

Without the 6 gears to choose from I couldn't make it up any of the hills around here or reach any decent speed. In order to achieve 50 mph I had to get a running start from the "other" side of the hill and so I started at a stop sign in first gear, shifted up to about third or fourth before hitting the crest and then shifting through to sixth gear as I started down the hill. This way my "peak power" was always in use rather than either underrev or overreving the motor. "Peak Power" occurs at a specific rpm all the time... that's what gives you that "extra"... because you are always near perfection as far as the motor rpms are concerned.

The "Peak Power" curve is the magenta colored line...

 

[Matt Gruber]

thanks! i misunderstood a previous post about the front sprocket.

 

[safe]

On my "transaxle" one of the teeth on the previous gear setup broke (I had previously bent the teeth inward because the chain was dropping between the two gears... I had welded them too far apart ) and so I decided to go ahead and increase my options by cutting away all the old stuff and adding parts from a rear freewheel to the "transaxle" instead. The freewheel started life with 6 gears and I cut that down to four in order to get them to fit. They are 14, 17, 19, 21 and don't forget that on the wheel itself I have 14, 16, 18, 21, 24, 28. I built that weird looking front derailler too. It's not really "runtime" configured (it uses a simple bolt and wingnut instead) but it could be if I really wanted to. (maybe later)

So much for "no more development" on this bike... it's like a "bad addiction"... once you start to "tinker" it's hard to stop...