* * * THE 40 MPH CLUB * * *

[safe]

This new club currently has no members.

When people actually prove that their bikes can go above 40 mph on flat land then they need to declare themselves as members here.

 

[safe]

My bike has passed the test to join the club and can exceed 40 mph on flat land.

So I'm a member of the "40 mph Club".

 

[Lowell]

47mph on the flat here...

 

[safe]

You have me beat. My top speed on the flat is right around 38-42 mph depending on conditions. We should be able to get a few people into this club because 40 mph is more easily attainable than 50 mph. And 40 mph on a regular bicycle is "enough" speed anyway...

On my mountain bike I know what 40 mph feels like on a downhill in the dirt and it's pretty darn scary. About 15 years ago I lived up in Squaw Valley (Lake Tahoe) for about 6 months and I used to take the gondola up with my mountain bike and race down their track. (they ran a qualifying session for the Summer Olympics that year so that was the track I was using) I'd bet that I was going 40 mph down that hill or better... it was insane... from top to bottom it was a 3000 foot drop.

 

[safe]

My calculations show that a fully legal 750 Watt bike with "good" streamlining, but not "perfect" (like the "impractical" full shell ideas) will yield a top speed of about 40 mph. So in the "long run" I really ought to be focusing on getting 750 Watt bikes up to 40 mph (which I already have) and then turning towards efficiency to get the range up.

A "nice" goal would be:

40 mph top speed.

40 mile range.

That makes for a bike that does what you need rather well without raising many flags in protest. When a manufacturer sells such a bike they sell it with a single speed at either 20 mph top speed or 30 mph depending on the laws of that state. The owner then simply changes the gearing around afterwards to suit their tastes... which might or might not include a multispeed internal hub. Since the national law requires pedals it's simply a requirement to have them so this would also have to be included in the design.

40 / 40 / Pedals

It's my new formula... (but I'll still build a "monster" speedster just out of curiousity as well)

 

[xyster]

Safe, if you'd add an easy, DIY-friendly upgrade path to another "4" stat, your project would be very compelling to me:

4 seconds 0-40mph!

 

[Lowell]

Safe, if you'd add an easy, DIY-friendly upgrade path to another "4" stat, your project would be very compelling to me:

4 seconds 0-40mph!

Wouldn't that require a very large power upgrade over 750W?

 

[xyster]

Wouldn't that require a very large power upgrade over 750W?

Yes. Which is why I suggested he leave the components and overall system as modular and user-upgradeable as possible. Maximize the market!

 

[Lowell]

Wouldn't that require a very large power upgrade over 750W?

Yes. Which is why I suggested he leave the components and overall system as modular and user-upgradeable as possible. Maximize the market!

Sounds more like 50/30/4/pedals

 

[safe]

The national law has three parts:

750 Watt power limit.

20 mph top speed gearing. (as sold)

Pedals are required.

You MUST satisfy all three criteria to be "protected" by this law in all states and for all legal issues. (like getting sued by someone) They created the law to protect the manufacturer so that they could build without worrying about local laws... though in some cases (like Boulder Colorado) the local laws are actually WORSE than the national ones.

So if you want the widest "blanket coverage" of legality you pass these three tests at the "point of sale".

And this points to the "modified" bike being able to reach about 40 mph "tops" on the flat. (based on aerodynamic limitations) So you want to "over" design the bike to handle a little more than that speed safely... like about 50 mph. That way the bike is "safe" for all conditons that it might be placed into... stock or modified...

So the "40 mph Club" is where the national "legal" (but modified after sale) bikes will fall into... the "Monster Speedsters" (2 hp or above) are the only ones that will ever make it into the "50 mph Club". The "Monster Speedsters" are really (to be honest) small motorcycles in how much power they are producing. This is true whether you are using a "Hub Motor" or a PMG 132 to get power... so the "Monster Speedster" is more of a "power" question. The laws will never allow above 750 Watts... PERIOD.

 

[Lowell]

Motorcycles don't even start to be fun unless they have 3 digit horsepower...

 

[xyster]

And this points to the "modified" bike being able to reach about 40 mph "tops" on the flat. (based on aerodynamic limitations) So you want to "over" design the bike to handle a little more than that speed safely... like about 50 mph. That way the bike is "safe" for all conditons that it might be placed into... stock or modified...

Whether using gears or not, I'd rather have a bike "geared" for 40mph top speed with quicker 0-40mph acceleration than 50mph with slower 0-40mph acceleration. Top speed constraints (at some point necessary on a normal bicycle due to inherently lousy high-speed handling) don't necessarily set an upper limit to power. The bike could have a 100,000kw motor but still top out at 40mph.

 

[safe]

Whether using gears or not, I'd rather have a bike "geared" for 40mph top speed with quicker 0-40mph acceleration than 50mph with slower 0-40mph acceleration. Top speed doesn't necessarily set an upper end to power. The bike could have a 100,000kw motor but still top out at 40mph.

But then you fail the first criteria... the LAW says 750 Watts. PERIOD.

Unmodified the "legal" bike can only go 20 mph.

So what I'm saying is for "legal" reasons you need to sell the bike with the "ability" to go 50 mph (based on handling) and yet sell it in the "legal" configuration to keep it inside the 20 mph law. (if someone modifies the bike after sale that's their own liability)

My main point is that you need to "design" for 50 mph and "sell" at the 20 mph speed. (and then actually "achieve" 40 mph on the flat when modified)

Even if you sold a "Hub Motor" design you need to design the bike so that it can HANDLE the 50 mph top speed with stability...

 

[xyster]

So what I'm saying is for "legal" reasons you need to sell the bike with the "ability" to go 50 mph (based on handling) and yet sell it in the "legal" configuration to keep it inside the 20 mph law. (if someone modifies the bike after sale that's their own liability)

Apparently you do not read posts very completely.

"I suggested he leave the components and overall system as modular and user-upgradeable as possible."

"if you'd add an easy, DIY-friendly upgrade path to another "4" stat, your project would be very compelling to me"

Do you understand I'm talking about leaving a bolt-on upgrade path for aftermarket parts which you'd have no compunction to sell yourself?

 

[Lowell]

And this points to the "modified" bike being able to reach about 40 mph "tops" on the flat. (based on aerodynamic limitations) So you want to "over" design the bike to handle a little more than that speed safely... like about 50 mph. That way the bike is "safe" for all conditons that it might be placed into... stock or modified...

Whether using gears or not, I'd rather have a bike "geared" for 40mph top speed with quicker 0-40mph acceleration than 50mph with slower 0-40mph acceleration. Top speed constraints (at some point necessary on a normal bicycle due to inherently lousy high-speed handling) don't necessarily set an upper limit to power. The bike could have a 100,000kw motor but still top out at 40mph.

Ideal gearing would be able to carry the front wheel on a launch. Anything lower than that would just be for stunting.

 

[safe]

Xyster

On your bike the power is definitely there to take you to 50 mph, but the handing is so bad (weight balance, rear wheel strength, short wheelbase, frame flex, etc) that you really can't use it all. (you've expressed fears to go even a quarter mile at full speed)

My bike does 50 mph and feels about the same as my old MB5 motorcycle that also could go about 50 - 55 mph. Despite what you might "fear" about more speed if your bike was designed for it there would be no problem.

Case in point:

In my old "Gravity Bike" days I was talking with a "retired" local road racer that was a machinist in town and he told me (as I was just a little 16 year old kid that didn't know anything at the time) that when he looked at my bike that he thought the wheelbase was too short. So I built my first long wheelbase bike and <<< WOW >>> all of a sudden the thing could go really fast and it felt "safe" to ride. On that bike I was "paced" with a car to speeds around 60 mph on a 10% downhill. It was smooth... and I was using TWENTY INCH wheels.

In skiing they have "short" skis for the slalom racing and "long" skis for the downhill. I'm basically making the same case here.

Wheelbase is everything when you are going fast... it's what determines the speed that the steering reacts... so you need to get the wheelbase "correct" for the speeds you are intending to go at.

The "well built" national legal limit bike should be designed to handle 50 mph without the rider "freaking out"... the motor choice doesn't matter... it's the frame design that counts here...

 

[xyster]

Safe

I know. That's why I put the adjective "normal" in the sentence:
" (at some point necessary on a normal bicycle due to inherently lousy high-speed handling) "

I doubt many off-the-rack bikes of typical (normal) wheelbase and typical price, like most people typically buy, handle well enough at 50mph to be safe at that speed from a handling standpoint. Do you disagree? If not, then once again after your lousy reading comprehension is sorted out, we agree we agree.

Are you actually planning to design and sell an all-in-one ebike with a custom frame you design and have manufactured? That's a very competitive market with high startup costs it doesn't seem any company has yet succeeded in. If not, you're talking about a kit. And if you're talking about a kit, you're talking about it being safe on the "normal" types of bikes people buy.

 

[safe]

The simplified thought goes:

"If you plan to modify your bike to have 'higher than stock' performance don't you want your 'base platform' to be able to handle the extra performance you add?"

 

[safe]

I doubt many off-the-rack bikes of typical (normal) wheelbase and typical price, like most people typically buy, handle well enough at 50mph to be safe at that speed from a handling standpoint. Do you disagree?

I agree 100%.

That's the PROBLEM that needs to be addressed. If you start adding all this extra performance (whatever way you go about doing it) it seems irresponsible to do so without taking into consideration the issue of higher performance induced high speed stability problems.

If people are seriously going to start adding all this "extra" stuff they NEED a platform that is solid enough to make what they are doing safe to ride.

 

[Lowell]

What is the design speed for downhill mountain bikes around 46" wheelbase? Seems to me a heavily built DH bike would make a good candidate for an electric conversion.

 

[safe]

What is the design speed for downhill mountain bikes around 46" wheelbase? Seems to me a heavily built DH bike would make a good candidate for an electric conversion.

Yes, I would suspect the wheelbase is longer and the loads that are expected to be absorbed would be higher. Downhill racers do 50 mph top speed to the best of my knowledge. They tend to be more "motocross like" than street built, so the twisting stress might not be so good. Asphalt provides much more traction so that gets transferred to the frame as flex. On the dirt the tires will tend to slide across the top more and so that relieves frame stress.

If you found a bike frame manufacturer that made a "big deal" about frame rigidity then that might be a great platform except they are a little high off the ground for street speed. Aerodynamically they are horrible.

The biggest problem with the hub motor concept with a mountian bike is weight distribution. Ideally you would run two small hub motors one front and one rear. Then divide your battery pack with 50% in the middle and 25% off the front and 25% off the back. These "back loaded" bikes aren't good. And being "back loaded" AND rear hub motored is going to make the thing handle terrible.

Don't forget that motorcycles have wheelbases around 50"+.

 

[safe]

Using:

http://www.kreuzotter.de/english/espeed.htm

...and with the default values for the bikes I come up with the following numbers for how much energy in Watts are required to get the various bike designs up to the "40 mph Club" level.

 

[xyster]

Nice chart, Safe. Very useful for visualizing aero info. It'd be nice to have different colored lines on the same chart representing different speeds -- 10mph,20mph,30mph, and the 40mph one already done.

 

[safe]

Membership Dues?

All clubs have "membership dues". The price to join the "40 mph Club" can be found in these charts...

 

[xyster]

I almost inadvertently became a member of the 40-and-over club today. Some asshole in a pickup purposely tried to keep me pinned in the bike lane while approaching street construction signs positioned smack in the middle of said bike lane. I moved over into the traffic lane to avoid the signs. He roared by me at 40mph through the construction zone, almost clipping my backside with his right mirror. So after getting through the construction area, I sped up to try and get his license plate. It was a 25mph zone and he was tailgaiting somebody else going 35mph in another truck in front of him. I couldn't quite catch up, but I'm happy to note that without wet roads or much wind today, the bike was perfectly stable this time at 38mph. And that was going up a ~1-2% grade in a full upright, no-tuck position. The bike had plenty of pep left, but approaching an intersection, I had to slow down.

The problem really is finding a safe area to go any faster, and a calm, dry day like today. I only have two front brakes, no rear brake. Stopping reasonably swiftly from thirty I don't think is much problem. Stopping quickly from forty may be a very big problem.