* * * Bike Designs and Theories * * *

[safe]

Let's throw some design ideas around...

 

[safe]

One theory I've worked on for something like 28 years now is the idea of the "sit and stand" bike (I remember having the idea at around 18 and reading a book on aerodynamics and running formulas to justify the idea back then):

On a downhill you want low frontal area and so you want a tight "sitting" tuck that gives better control and aerodynamics at the same time.

On an uphill you get off the seat and pedal while standing up. This is not the "ideal" way to climb hills, but it's not terrible if it's for short distances. If the hill is long and not very steep then you can rely on the motor to pull you up, but for those "power deprived" situations when the motor starts to get hot and "yell" for help this is when you stand up and pedal.

 

[safe]

(from another thread) Unless it's 20amps or less you're already above the legal 750 watt limit.

That's a fine point of the law I guess. "Whatever it takes" to comply would be my position on it. It would also be preferable to sell the bike with a 20 amp controller anyway because then you get better range and since you could pedal on the uphills that "solves" the torque problems.

So I could see going on "separate paths" of development with one path flirting with 60 mph speeds and the other staying within the more restrictive laws and seeing what can be done there. If I went with Lithium on the "pedal bike" and a low current limit then the battery pack could be very small and very lightweight. How about this:

36 Volts 20 Amps
Lithium Pack of 60 cells 10 x 3 x 2 - (13.2 AH)
Weight is only about 8 lbs
Total Price only $282

This would give a top speed of about 30 mph even with gears and a runtime of about an hour or 15 miles, more if you pedal, and this would all be done with an 8-speed when 30 mph limits are accepted. To be 100% compliant with the 20 mph law you sell it with a single speed on the rear.

At prices like that you could sell a lot of them because the battery doesn't scare people away. ($282 verses something like a $800 for a bigger machine)

On a downhill the bike would still be "smoking fast" since it would have the fiberglass and low frontal area. You "sit down" to ride and "stand up" to pedal. (because the seat needs to be almost a foot too low for pedalling while sitting) Note the long wheelbase too... no worries on the "big downhill" where you actually have your fun...

 

[knightmb]

That's a fine point of the law I guess. "Whatever it takes" to comply would be my position on it. It would also be preferable to sell the bike with a 20 amp controller anyway because then you get better range and since you could pedal on the uphills that "solves" the torque problems.

So I could see going on "separate paths" of development with one path flirting with 60 mph speeds and the other staying within the more restrictive laws and seeing what can be done there. If I went with Lithium on the "pedal bike" and a low current limit then the battery pack could be very small and very lightweight. How about this:

36 Volts 20 Amps
Lithium Pack of 60 cells 10 x 3 x 2 - (13.2 AH)
Weight is only about 8 lbs
Total Price only $282

This would give a top speed of about 30 mph even with gears and a runtime of about an hour or 15 miles, more if you pedal, and this would all be done with an 8-speed when 30 mph limits are accepted. To be 100% compliant with the 20 mph law you sell it with a single speed on the rear.

At prices like that you could sell a lot of them because the battery doesn't scare people away. ($282 verses something like a $800 for a bigger machine)

On a downhill the bike would still be "smoking fast" since it would have the fiberglass and low frontal area. You "sit down" to ride and "stand up" to pedal. (because the seat needs to be almost a foot too low for pedalling while sitting) Note the long wheelbase too... no worries on the "big downhill" where you actually have your fun...

Sounds good, but how do you get batteries that good for only $282? I know another person from China is willing to sell some Lith packs for over $630 + $70 for the charger, might want to send him a message. Any idea how much the rest of the bike parts would cost?

http://endless-sphere.com/forums/viewtopic.php?t=293

 

[safe]

Lithium Cells

$4.69 * 60 = $281.40

All the rest is extra of course.

It's "safe" to say that 60 cells will always cost LESS than 120 cells...


http://www.all-battery.com/index.asp?PageAction=VIEWPROD&ProdID=554

 

[Ypedal]

My personal view on the subject.

Go on google and search " Freeride "...

Expensive.. yes.. heavy.. yes... STRONG ? .. ohhh yes...

Why re-invent the wheel.. just walk thru your LBS and look at all the frames available.. some are better suited than others....

10mm dropouts..

135mm for non-disk.. 150mm for disk brake

Battery mounting.

Throttle friendly controls

Seat/handlebar position depending on your needs and age.. lol..

Good quality suspension so you don't do the pogostick thing.. and it can be adjusted to handle the weight of batteries.

I picked my 05 Norco Chaos out of another 100 frames available.. there was a " Specialized " that was almost as good.. but was another 1000 $ more.

 

[safe]

Some better pictures of the "sit and stand" concept...

 

[xyster]

Lithium Cells

$4.69 * 60 = $281.40

All the rest is extra of course.

It's "safe" to say that 60 cells will always cost LESS than 120 cells...

These cells are rated 1.5C, but due to uneven power use in parallel packs, it's much safer to run them at 1C.

patrick_mahoney has a 12s8p pack of these that, last I heard, were working peachy-keen with his 20 amp controller (1.1C).

So if you were serious about this safe, at 20 amps plan at minimum 8 in parallel -- for 36v 80 cells total.

These can be found for around $3 per cell if bought in lots >100 and a 10-12% off coupon (very common) is applied. That's how I bought mine.

For $45 all-battery also sells 10-cell (in series) BMS's with a peak 27 amp rating -- one of those should work great with an 80 cell 37V ~16ah pack:
http://www.all-battery.com/index.asp?PageAction=VIEWPROD&ProdID=909

For inexpensive lithium packs less than 16ah, you could choose batteryspace's 1.3ah 10C a123-knockoffs for ~$6 each:
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=3071

But with these ~3.2v cells you'd need to come up with your own charging solution, or use an RC charger with settings for lithium iron phosphate cells (of which there's a couple now).

 

[safe]

Why re-invent the wheel.. just walk thru your LBS and look at all the frames available.. some are better suited than others...

Because I learned 20+ years ago that bicycles use a wheelbase that is waaaaaaay too short... like 10" too short for real high speed riding. While the bike must pass laws for flat line speeds at the "point of sale" the idea is that people modify them or use them as "Gravity Bikes" that don't need a "tow" to get to the top of a hill. You can pedal to the top of the hill with the motor assisting you (which makes that part easy) then you get into your "tuck" and hit speeds of 50 mph or more going down it.

The longer wheelbase makes the bike easier to stand up and pedal on too because it slows the steering down a lot.

Trust me... I been doing this for over 20 years now... it works...

 

[safe]

For inexpensive lithium packs less than 16ah, you could choose batteryspace's 1.3ah 10C a123-knockoffs for ~$6 each:
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=3071

I do like the looks of those...

 

[Mathurin]

If you have to stand up at all to pedal hard on a DF, your seat is too low.

Recumbent designs address the normal vs. crouched problem safe's design suffers from.

More may be icing, but 500w of power is quite a lot on a bicycle.

Some power-assists assist a lot, but no human input = not a bicycle.

Most bicyclists seem to ride at somewhere around 15mph, something that goes 60 is in a completely different time zone.

It's a terrible bicycle that's too heavy to be carried up a flight of stairs, installed on a car rack, etc.

 

[xyster]

It's a terrible bicycle that's too heavy to be carried up a flight of stairs, installed on a car rack, etc.

I doth protest! It's true my bike is too heavy to carry, or attach to any common car rack, but it pedals just fine and quite normally. I often use it without any assist for 5-6 mile exercise rides. On the plus side, being too heavy for one person to easily carry, it's less likely to "walk away" from a bike rack.

 

[TylerDurden]

It's a terrible bicycle that's too heavy to be carried up a flight of stairs, installed on a car rack, etc.

Ditto on that...

Even with my lead taken off, my bike still weighs 60lbs. I put that on the car-rack at least twice a week.

I look forward to building a lowrider that breaks-apart for easy loading (not while riding).

 

[safe]

Recumbent designs address the normal vs. crouched problem safe's design suffers from.

But the known handling concerns about low center of gravity on the recumbent makes the recumbent not desireable for "Sport Style" riding.

On the uphill you want to be able to "stretch your legs" as you do the hill climb. On the downhill you want to be in a postiion to be able to react with "body english" to bumps in the road and sliding around. The recumbent just doesn't have the physics right (so says wikipedia) to handle "well" when things get scary:

http://en.wikipedia.org/wiki/Recumbent_bicycle#Disadvantages

"Balance. Balance is easier to effect with a higher centre of gravity, because of the "pendulum effect" (it is easier to minutely change the angle at which ordinary bicycles lean).[5] The lower center of gravity makes two-wheeled recumbents harder to balance, especially when moving slowly or on unstable surfaces. If a wheel slides, the bike will typically go down very fast. Where one can change one's weight from the seat to the pedals on an ordinary bicycle, one's weight is only on the seat while riding a recumbent. This ability to shift one's weight and place weight on one's feet is an important part of the difference in balancing an ordinary bicycle and balancing a recumbent.

Hills. A perceived disadvantage of the recumbent position is that the rider is unable to stand on ascents. This is most noticeable during the initial period of riding a recumbent when the muscles are not yet trained for the different muscle recruitment. Offset against this, the rider can push against the seat to generate more pedal force than is possible on an upright bike because on an upright, the rider cannot press a pedal downward with any more force than his own weight. As with upright bikes, higher cadence reduces leg strain and fatigue when climbing. A few designers have attempted to build bikes which convert from recumbent to upright for climbs. In practice the biggest difference is probably the additional weight of the recumbent layout combined with the difficulty of balancing a bike with a low centre of gravity at speeds below about 5mph; the idea that recumbents inherently cannot climb is regarded by recumbent riders as a myth as recumbents have won hill-climb challenges and races with substantial ascents against uprights in mixed fields, and have been ridden over the mountain stage routes of the Tour de France.

Riding position. The riding position, while comfortable and removing stress from the arms, cannot easily be varied during a ride (as upright riders might stand for a hill), and some find that bottom brackets at or near hip level produces problems with cold or numb feet. Some riders suffer "recumbent butt", a pain in the gluteal muscles caused by their working harder while being compressed. This can usually be addressed by adjusting the seat angle and pedal position. Another disadvantage is the eye offset: the distance between the eyes and the front end is quite a bit larger, and in addition, you don't have the option of leaning forward. This leads to a bad insight angle at sharp corners. (Car drivers have the same problem, though less acute since they are closer to the middle of the street.) It's also a bit more difficult to glance back.

However I'll add that the "sit and stand" concept suffers from one problem in that after you complete a hill climb your legs don't particularly like being tucked afterwards and prefer a more stretched out position because the circulation is better. This is the #1 drawback to "sit and stand" with the electric bike, but as with all things there are advantages and disadvantages. I've found on my previous "sit and stand" road racers (from back in the 1980's) that your legs feel okay about 30 seconds after you crest the hill... so one might simply stop pedalling as they approached the crest and let the electric power take over (wiggle your legs a little while standing up)... then once the speed starts to build up on the downhill you get into the tuck.

Bobsledders do something similiar... they have to use their muscles first, then jump inside their sled and get kind of "cramped".

 

[xyster]

"recumbent butt"

The ubiquitous affliction of couch potatoes everywhere.

<font size="-2">The wording of that statement was superfluously redundant -- oh well.</font>

 

[safe]

Variations on Stokemonkey

With the Stokemonkey system the "peak power" of the motor and the "peak power" of the human pedalling are "supposed" to be in line with each other. I'm thinking of making a mild variation on that theme because the main time to pedal is when you need to get up hills. If I shift the pedal power down a bit it suddenly allows me to climb with a taller gear than I might normally need. Overall it makes the motor run in the higher rpms and the human power comes in at the lower rpms. This way the rider would be in a situation of "boosting" the bad areas rather than magnifying the good ones. (you don't have to worry about the "no load" condition because you would "rev yourself out" well before that takes place)

I'm not sure if this is good or bad yet.. hmmmmm...

I've got a variable on my spreadsheet to move the pedal area back and forth in the powerband and run "what ifs" on it. By shifting low I can all of a sudden tackle 15% slopes with a very low controller limit.

 

[safe]

Chain Alternatives

Most people think:

"I want to be able to pedal and then MAYBE I might add a little extra motor power sometimes to help out." (Stokemonkey style)

...but what if instead you think:

"I want the motor to be the primary energy source and I MIGHT pedal to add a little extra power to the motor when it gets bogged down on a hill." (Sit and Stand style)

Solving these two "opposite" design goals would be accomplished as in the chart below. Note how in the "Sit and Stand" style the motor is "direct drive" to the rear wheel thus allowing the second chain not to move unless the rider is pedaling. That's a 50% reduction in chain related drag. The freewheel that unifies the pedal crank to the motor would have minimal drag. (virtually none) This would boost efficiency for the chain to near 95%.

The "Cyclone Style" is good too, but it places the motor in a position that is (for my designs) awkward. (that's where the motor connects directly to the main bike chain) Another drawback is that you are more closely tied to a chain speed that would require a lower rpm motor speed. The "Cyclone Style" has merit and I wouldn't rule it out. (it would be nice to have just one chain rather than two, even though the second one is not used most of the time for "Sit and Stand")

 

[Geebee]

Safe, you really need to try out some recumbents, choppers.
Do you realise what a huge range of bikes recumbents cover? Lowracers, highracers,trikes streamliners, lwb's, swb's,velomobiles and assorted others.
I have a chopper style recumbent that will drop any upright push bike through a corner on sealed roads, it is quite happy well beyond 45 degree lean in a corner, I have had cars lockup when they realised they could not corner at that speed, similar response on a trike if you are good at body english although not to the limit of the bike.
Oh and it breaks one of your other rules the batteries are inches of the road on the bottom of the frame.
Your sit and stand machine could not remotely approach the speed of a streamliner or even a velomobile on the flat or downhill.
Also I for one could not ride your style of bike uphill as I have a rebuilt knee and arthritis, yet I can blast along in complete comfort on my recumbents and not so comfortably on wedgies.
Yes recumbents are slower uphill but if the hills are rollers you will never see a velo or streamliner after the first roller.
I have not ridden your style of bike but it is close to the only style I haven't tried.

 

[Malcolm]

Your sit and stand machine could not remotely approach the speed of a streamliner or even a velomobile on the flat or downhill

This is why recumbents are excluded from most racing events. If you're not happy about the balance of a recumbent bike, you could always build a recumbent trike, like Geebee's. They're fairly easy to build for someone with your fabrication abilities. They have good stability, but also require plenty of body English to get the best out of them. (Although if you place plenty of lead low down a trike should be virtually untippable). They have excellent aerodynamics and they provide lots of space for stowing batteries and playing with different gear configurations.

 

[safe]

Also I for one could not ride your style of bike uphill as I have a rebuilt knee and arthritis, yet I can blast along in complete comfort on my recumbents and not so comfortably on wedgies.

You have a good point on that one. I played "club level" Volleyball for about 10 years and all that spiking and then landing has produced an injury to the tendons of my left knee that makes my knee sore when in a "tuck" position for a long time. So my own bike makes my knee sore if I ride too much. (I'm 46 years old now and the body is getting sore in a lot of places)

So that's a strong argument... people who's health is not so great can ride a recumbent more easily.

 

[safe]

If you're not happy about the balance of a recumbent bike, you could always build a recumbent trike, like Geebee's.

That's a good idea.

I'd feel more comfortable being that low and having three wheels than trying to steer through corners knowing that the normal fraction of a second reaction time that you normally get on a "road racer" is now cut in half or more. From what the technical analysis of the low center of gravity suggests you basically will crash before your body can even realize what is happening if one of the tires slides. On my "road racer" I've already gotten into a few slides (small) at speeds of about 25 mph and the bike very smoothly regained traction and straightened out. No major "high side" or anything just a progressive chatter and then catch.

So I'd build a trike before a recumbent...

But I'm also thinking of selling these things potentially and kids like "cool stuff" and the "road racer" looks cool. With fiberglass and hot bright paint it will be like candy for the kids. (kids of all ages :wink: ) I would think the "target audience" for my bikes are the 14 - 21 years olds that want to get around, but don't want the hassles of a motorcycle license yet. Maybe even some young people who don't want a car at all and still want to get around and have some fun while doing it. I'd see this as a "bridge" to the larger (electric) motorcycle or car or in many cases simply a "sport pleasure" unrelated to practical need.

 

[Lessss]

GeeBee. We DEMAND pictures!!

 

[safe]

This is a nice chart. In it I'm assuming that as the pedal rpms increase from 40 rpm to the peak of 100 rpm that the human powered "effort" drops from 200 Watts (at 40 rpm) to zero at peak. Somewhere in the middle you would find a "balance" that would be the actual speed that you climbed the hill. The faster you pedal the EASIER it gets (since the motor helps out more) so you have a sort of built in "incentive" to get the power up into the better efficiency areas for both yourself and your bikes motor. This is more like the "Stokemonkey" configuration.... which is actually the best I think...

Talk about "wide powerbands". The addition of pedaling to the low end would essentially eliminate motor heating. That's a nice little "extra" for being able to pedal.

Another "interesting" observation is that you could gear a single speed to hit 40 mph on the top end and in order to "get there" use the pedal power "boost" to get you up to speed. My calculations show that even with a tall gear that will get you to 40 mph with 500 watts of pedal effort you could still climb a 10% slope. So the powerband "expansion" is very impressive and it really adds to the "sit and stand" concept. For speeds BELOW 20 mph you pedal while standing up and get hit by the wind... for speeds from 20 - 40 mph you let the bike to all the work and actually save "overall" effort with less wind resistance. It's a true "win win". :wink:

The 8-speed gearing ends up just being gravy...

 

[Mathurin]

Tried to guesstimate charts of what I think I perceive in pedal power.


Approx. power band:

Approx. RPM vs time to exhaustion:

Power vs time to exhaustion:

Unite MY1018:

Right then, I've been thinking the 250w MY1018 could be good if crank mounted with an internal geared hub at back.

The way I would use it is pedalling around 90 most of the time, like when commuting and stuff, and every now & then I'd hammer around 120 for a few mins whenever I want/have to, ie: there's some other dude on a bike I want to beat, I want to ride in with the traffic for some reason, or maybe I'm warmed up and just feel like it, etc... But the point is that pedalling at 120 is something I do when I want to go faster.

So here's the problem: The MY1018 would get revved out and put out less power when I want more of it, or it would be bogged down wasting eff needlessly when I'm using it as I would most of the time, cruising along, because it's power band is ass backwards compared to the human part of the drive line.

Now I'd much rather have something that actually complement the human part of the drive line, unfortunately with the crank drive the only way I could think to circumvent it requires the use of a derailleur to change the proportional ratios depending if I'm cruising or pushing. But a derailleur is something I strongly prefer to avoid. So, the other solution I thought of was to mount it on a geared hub up front, this one has the double advantage of introducing a freewheel to the works, that would be absent in the crank mount config.

 

[Leeps]

speed controller?
Joe