Extreme Hill Climber Fat Tire MTB Project.

[Alan B]

A hill climbing application would be better served with a mid drive. With a BBSHD, for example, a full rear cluster could be installed, and a single front chainring. This could easily cover a 3:1 or more gearing range and get the motor operating at a higher RPM while providing the rider with proper pedaling cadence.

[commuter ebikes]

A hill climbing application would be better served with a mid drive. With a BBSHD, for example, a full rear cluster could be installed, and a single front chainring. This could easily cover a 3:1 or more gearing range and get the motor operating at a higher RPM while providing the rider with proper pedaling cadence.

Yes, gearing is a great thing. I agree with you about the mid drive for a better range of gears, but I had three Cromotors laying around. I will use the motor to travel 7.3 miles at 35mph to the trailhead and maybe not use the motor at all in the park, if I can resist turning on the motor. Hopefully this extremely low gearing can pedal the 350 pound bike + rider + cargo up the steep hills.

I was able to get five wheels built with the dishing off by 2-4mm with the tire biased toward the drive side; if that tire rubs the frame, I will have to run a slightly more narrow tire in the rear. The spoke tension values (on the Park Tool TM-1) are between 15 and 30 units. Back to Alan's point, a mid drive leaves the front and rear unmolested. On most bikes, the area on the drive side between the hub and axle nut has so many parts competing for space. I envy you mid drive guys, but I am so paranoid about a cop seeing any electronics because I am afraid they will confiscate my rig.

The electronics tech found physical damage on one of my 36V batteries. Some of the strips to popped off the cells. This may have occurred when the battery fell off a stool while I had it in the garage. The electronics tech will spot weld the strips back on.

[Sneakers915]

No cop is going to confiscate your bike, at most you'd get a ticket and even that seems very remote. You're in CA, ebikes are legal pretty much anywhere aren't they?

[commuter ebikes]

No cop is going to confiscate your bike, at most you'd get a ticket and even that seems very remote. You're in CA, ebikes are legal pretty much anywhere aren't they?

We have the three levels that are legal, and all of my ebikes are above both power and speed levels. When I built the bikes, I built exactly what I wanted; apparently California thinks that is too much power and speed. As such, it is an illegal homemade motorcycle. It would be at an officer's discretion to warn, ticket or confiscate. So that is why I have always been so careful to hide the motor, battery and controller and always pedal.

In practice, however, I ride this around everyday and I have never been pulled over. The cops either don't notice the bike, or if they notice I often get a smile.

I'm sure the key to avoiding legal problems is driving safely. Blowing through a stop sign or driving like a jerk would make a terrible impression.

[Alan B]

A Cromotor is a wonderful thing, but very heavy, and mounted in those huge wheels it is really not a good fit for dirt trails. The current required to spin those big tires on steep hills with lots of weight to carry is going to make it very hot. It is just the wrong choice. We actually already proved that there in Marin on that day, the BBSHD made it up the hill and didn't get warm and the Cromotor was getting too hot and didn't really have adequate torque, and that wasn't as steep as those roads get.

I would abandon that plan, it is just going to soak up a lot of effort and funds and deliver a poor result with insufficient torque and excess axle weight.

A BBSHD or Cyclone would be more fun and give you lots of pedaling gears, and make a lighter bike. I would think you could easily trade a Cromotor for a Cyclone so not have to spend cash.

[commuter ebikes]

A Cromotor is a wonderful thing, but very heavy, and mounted in those huge wheels it is really not a good fit for dirt trails. The current required to spin those big tires on steep hills with lots of weight to carry is going to make it very hot. It is just the wrong choice. We actually already proved that there in Marin on that day, the BBSHD made it up the hill and didn't get warm and the Cromotor was getting too hot and didn't really have adequate torque, and that wasn't as steep as those roads get.

I would abandon that plan, it is just going to soak up a lot of effort and funds and deliver a poor result with insufficient torque and excess axle weight.

A BBSHD or Cyclone would be more fun and give you lots of pedaling gears, and make a lighter bike. I would think you could easily trade a Cromotor for a Cyclone so not have to spend cash.

I'm afraid I have a bit of a mania about needing to hide my motor, controller and battery. I fully recognize that this mania is a weakness on my part. So within the confines of a rear hub motor, one wonders if I could depend on the extremely low gearing of the drivetrain and a reduced power setting in low and medium settings of the 3-speed switch. I just lost 55 pounds and I hope to lose 55 more, so that will help with the weight penalty of the Cromotor. A Cromotor weighs about 13.4 pounds more than a Cyclone, which I imagine gives the Cromotor a better ability to produce power and, more importantly, manage heat.

I also have a stipulation that all of my ebikes have the same motor and controller with interchangeable batteries, harnesses, and as many other bike parts as possible. These Hillclimbers that I am building differ only in the frame, chainring, freewheel, headset, axle width and lack of derailleur and trigger shifter. I need to minimize the amount of spare parts because I stock spare parts and there is only so much room in my garage.

I wonder what power settings will be low enough to keep the motor under 100 degrees C while climbing steep hills. On the street, I can run a continuous 2.5kW without overheating. Going up a steep hill and pedaling with the single extreme granny gear (1-7 mph pedaling range) , I will be curious to see how much continuous power I can run and still keep the motor temps in the double digits. If it does get over 100 degrees, I could turn off the motor and just pedal while the motor cools. I think I will designate both the low and medium settings in the 3-speed switch the task of climbing steep hills.

[Alan B]

For continuous operating at near zero speeds the power limit is probably in the 500-700W range. Battery current will need to be limited to about 10 amps max, perhaps less. Experimentation will be required to find out.

Here's some comparison data for some of my ebikes awhile back:



Here are some very rough approximate numbers for near-stall uphill trail speeds:

Assuming bike and rider and gear weighs 330 lbs,
A gradient of 20% makes the load about 700W at 5 mph,
The thrust required just for the gradient is about 55 pounds

The CroMotor above has 23.5 inch tires and a 120 motor amp controller and produces about 90 pounds of thrust max at near zero speed. If we convert this to 29" tires the thrust drops to 75 pounds due to the large tire penalty. Limiting the heat to about 700W for continuous operation in this mode is about half as much as the max shown above, so about 0.707 times the current and thrust, or 85A and 50 pounds of thrust.

With the Cromotor at 5 MPH fed with 700W all of the power will go to heat because 50 pounds of thrust will not move the bike against 55 pounds of gradient load. With the Cyclone operating at decent RPM through the gears, perhaps 20% of the power will go to heat. The power dissipation is primarily related to the surface area of the motor, so the Cyclone can dissipate about half the Cromotor. So if the Cromotor can dissipate 700W and just sit there stalled whereas you can feed the Cyclone 1500W and it could dissipate 300W while it is doing 1200W of work which is enough power to climb the grade at something like 9 mph. With the Cromotor you will only need about 5 pounds of thrust from the pedals to get moving at low speeds since the Cromotor is putting out 50 pounds (and getting very hot). So you won't need the low gears with the Cromotor on, it will be about like pedaling on almost level ground. With the Cromotor off your pedaling effort will increase by a factor of 11.

This is about the same as the Bonanza was with only rear wheel drive. Going to 2 wheel drive totally changed that. Since one motor pretty much cancels the gradient, the second motor is operating like it would on a level surface, and the total of the two are capable of more speed than most trail conditions allow. Also both motors run cool since they are not stalled anymore and have better airflow and the heat dissipation has doubled while each carries half the load.

Estimates and Calculations subject to errors and approximations. :)

[commuter ebikes]

So helpful!

[commuter ebikes]

I have had my nose to the grindstone for the last few weeks, and I have made enough progress to post an update:

(1) All of the wheels are laced and trued. The last wheel had a rim bent in three different places (because I was jumping like a moron), so it was almost impossible to true. The best that I could get the dish is 6.5mm (biasing the tire toward the drive side). If I ever want to do more jumping, I will use that wheel. If I can commit to staying on the ground, I will replace the rim which is a project in itself because the Rolling Darryl rims are only seasonally available, and I would have to drill my own cutout holes and then refinish the rim (I powder coat it).

(2) The controller heat sinks are built. I had to buy a 1-7/8" hole saw. I took them to the powder coater.

(3) I built the battery boxes. My friend who was doing it for me got a girlfriend, so he became too busy to do it.

(4) My electronics tech converted my two CAs from DP-S to DP.

(5) The same electronics tech fixed a 36V battery that suffered physical damage causing many spot welds to become separated.

(6) I amassed a large stockpile of 6 conductor stranded cable for my harnesses.

(7) I got a spare White Industries 23t freewheel and another freewheel removal tool which I will modify differently than my previous tool modification. That freewheel removal tool, as it comes from the factory, will not fit over the fat Cromotor axle. This time I am going to drill the hole larger (last time I shortened the tool). We'll see how this bit https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1 drills through the case hardened chromoly tool steel.

The powder coater is taking a LONG time to powder coat the two frames and small parts. It has already been about 6 weeks. One time they took 10 weeks.

I am currently making five master harnesses, any one of which can be used on any of my four bikes.

Once I get the harnesses built and the frames back from the powder coater, I have all of the other parts needed for assembly. We'll see what new problems arise upon assembly.

[commuter ebikes]

Here are the goods:

[commuter ebikes]

The powder coater says that they are swamped. They have had my two frames and small parts for two months, and they said that it might take another three months. I was trying to finish all of my tasks before the powder coating was done, but all I have left is redoing the harnesses so I will probably end up waiting on the powder coater with nothing else to do.

For my wiring harnesses, I had to buy 30 more of these connectors: http://www.allelectronics.com/item/c...%3A1%3BN%3B%7D.

I bought https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1 and https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1.

I modified another one of these tools http://www.bikeman.com/WIND-FWTOOL.html. The cobalt steel bit would not cut the tool steel, but I used a stone on a large die grinder which worked very well.

This won't be the first project which is delayed and waiting on the powder coater. I am very glad that I have two other bikes to ride while I wait...and wait.

[commuter ebikes]

Here is part of one the harnesses. It is a six conductor 22AWG stranded cable with precrimped connectors which is the wiring for the temp sensor, e-brake (regen) and ignition. I need to make five of everything, so it takes a long time.

[calfee20]

There has to be a better way to do this. Those connectors come with pigtails so they have to be soldered. They are also not water proof. You need an electrical system that uses a crimper and will provide insulation strain relief and sealing in one step. All of the auto manufacturers use these sort of connectors.



Something like this.

When you work for an auto dealer the manufacturer will provide kits to repair their style of connector. Then there are individual part numbers for the pieces to resupply the kits. This is the experience I have had in various dealerships.

It would be nice to keep things compatible with the connectors that come with the controllers or your Cycle Analyst. However if you are looking for water proof then maybe something from an auto parts store or something that can be ordered from the US.

Maybe something like this? Disclaimer........I have no personal knowledge of this company. I just ran across them with some web searches. http://crimpsupply.com/packard-delph...metri-pack-280

[commuter ebikes]

There has to be a better way to do this. Those connectors come with pigtails so they have to be soldered. They are also not water proof. You need an electrical system that uses a crimper and will provide insulation strain relief and sealing in one step. All of the auto manufacturers use these sort of connectors.







Something like this.

When you work for an auto dealer the manufacturer will provide kits to repair their style of connector. Then there are individual part numbers for the pieces to resupply the kits. This is the experience I have had in various dealerships.

It would be nice to keep things compatible with the connectors that come with the controllers or your Cycle Analyst. However if you are looking for water proof then maybe something from an auto parts store or something that can be ordered from the US.

Maybe something like this? Disclaimer........I have no personal knowledge of this company. I just ran across them with some web searches. http://crimpsupply.com/packard-delph...metri-pack-280

Great point. I like to order from All Electronics, and they sell those exact "weather pack" connectors: http://www.allelectronics.com/index....D=weather+pack.

Unfortunately, I am broke now due to spending so much money on this hobby, so I will just have to put heat shrink tubing over my precrimped "locking connectors w/leads": http://www.allelectronics.com/index....tors+w%2Fleads. I have been using these precrimped connectors on all of my bikes for years, and I have never had any kind of failure. I just spent the last of my money on a full inventory of these, as well as a lot of heat shrink tubing. At the time of my connector purchase, I considered the weather pack connectors, but the increased cost was a financial issue. In retrospect, I should have bought the weather pack connectors and the proper crimping tool http://www.allelectronics.com/item/c...nectors/1.html with the money I spent on heat shrink tubing.

Here is a cool instruction sheet for crimping: http://www.allelectronics.com/mas_as...r_crimping.pdf.

[Alan B]

I have one of those connector kits from allelectronics. Those connectors are a bit large, I haven't used them much. They are a bit big for ebikes.