DIY College EBike

[A-DamW]

Agreed! That's why I'm amazed at this spindly rack on my daily cruiser has held up for 10,000 miles and going strong. It has not only a 14s6p pack on it but all my tire repair/tool stuff and saddle bags that I load clothes and groceries. It's steel where everything else seems to be aluminum.

Steel has an essentially near infinite cyclical fatigue life, if kept below a certain threshold.
Aluminum, and some other metals, will cycle fatigue to failure no matter the threshold of stress.

You can extend the life of aluminum by stressing it less, but it will never be as durable as steel.

Fun entertaining video by Fortnine
Motorcycle Metallurgy - Why Steel? Aluminum? Titanium?

Steel is real...

 

[raylo32]

An old guy's advice for the college student: for reliable transport get another bike and install a mid drive like a Photon. You can install it in an hour and it will do ~40 MPH if you need to and have a good enough battery. Lube the chain once in awhile and you are good to go. No issues changing flat tires. Then keep working this hub motor bike as your hobby or science project. This is the same advice I give my brother who likes to buy old BMWs for his daily drivers, which are always problematic with engine codes, busted window mechs, leaking air conditioning, etc. and need constant attention. That's OK for a hobby car/bike but when you need to be somewhere on a regular basis you need reliable transport.

 

[GoFastGus]

The main issue with that rack design is there is no solid mount to the seattube or seatstays. The "twisty" bits of flat metal are very flexible, and allow the rest of the rack to move / sway.

That rack is better designed than the one you're using, mostly because it has a secure "toptube" that clamps to the seattube to minimize lateral sway.

Gotcha, I’ll keep looking for designs like that.

LS is what breaks racks in the way Diggs shows.

(it can be exacerbated by using the rack as a handle for manipulating the bike, or lifting the rear end, as this adds other stress cycling to it).

I definitely do that, so that’s gonna stop real quick.

Steel racks will be better than aluminum for this kind of issue, because you have more of a chance to see a deformation before failure. Aluminum can show some stress cracks before complete failure, but it doesn't always do that. :/ The cracks can be completely inside it until failure.

I’ll look for something made of steel with a stronger design.

But preventing LS of the rack is even better, which requires a different design.

If by jump seat you mean something for a passenger, then keep in mind that every bump you hit multiplies the weight on the rack by however much force that bump creates (which is also related to your speed when you hit the bump, size of the bump, etc).

So a rack rated for say, 50lbs, with a person on it, will already be doubly overloaded, and every bump may place two to ten or more times the load on it at peak. It may not fail immediately, but it will be stressed beyond design limits each time, which can cause fractures or deformations, etc. (see my various posts about racks for different situations, including pics of one of the "indestructible" racks).

The one I linked to is rated at 165lbs. If I’m going over bumps in with two people’s weight on the seat and frame, I imagine the integrity of the frame is going to be a concern?

Also, the points to which the rack is mounted must also be designed for / capable of whatever load and type of loading is going to happen, or they themselves can fail. (I've broken frames at the seatstays from the lateral loading of an "indestructible" rack, such as the one I used on DayGlo Avenger).

Hmmm, that’s a good point. I’d rather something else break first before the frame.

 

[GoFastGus]

If you say so. E-bikes aren’t that fast. You need a motorcycle to go fast. No balance issue at 50mph+ though, so I guess you mean higher speeds than that.

How much above 50 have you not seen balance issues? This bike approaches 50mph on an open flat road

So you’re carrying a big ass wrench for swapping out your tube?

I’ve swapped tubes before, and all I’ve used is the tools to take the wheel off the bike (11 & 21mm sockets in the rear on this bike), tire levers, and a bike pump. Am I changing my tires incorrectly?

 

[GoFastGus]

Never thought to use wire nuts on an ebike installation. Never will either, though I guess for testing purposes a maybe.

Why’s that? Is it a safety issue or something else?

 

[GoFastGus]

If you have to use something like wire nuts, I recommend Posi-lock, like these:

Amazon.com

View attachment 379622
While experimenting with different motors and controllers, I used them successfully on phase and battery wires (and much smaller ones for low current/voltage signal wires) for a while (couple of years?) on the SB Cruiser, in our usually-dry desert environment but with occasional flash floods that submerges all that wiring under the trike while riding home for a few minutes at a time).

Gotcha, I’ll check these out! I try to wrap or keep wiring in a bag, so that’ll hopefully minimize the effects of rain and snow.

 

[GoFastGus]

have no place on an ebike, or any vehicle subject to movement and vibration. Same goes for solid copper conductor wires (except for motor windings.)

Gotcha! I’ll look for crimps or other connectors then.

Soldering is an art form, as is crimping. Look at some good YT tutorials, learn, and practice. Also helps to use good tools and materials. Avoids similar problems in the future.

Good advice! I’ll keep practicing, learning, and asking for help and advice.

 

[GoFastGus]

Here’s a short list of basic e-bike and scooter connectors that’ll really help clean up your wiring and make it look more professional.

2/3/4/6 pin Connectors

Pardon Our Interruption...

Bullet Connectors

https://www.ebay.com/itm/375369838803[/URL

I’ll definitely need something like this, thanks!

 

[GoFastGus]

Steel has an essentially near infinite cyclical fatigue life, if kept below a certain threshold.
Aluminum, and some other metals, will cycle fatigue to failure no matter the threshold of stress.

You can extend the life of aluminum by stressing it less, but it will never be as durable as steel.

Fun entertaining video by Fortnine
Motorcycle Metallurgy - Why Steel? Aluminum? Titanium?

I’ll take a look at this, thanks! My best bet might just be making a bike rack the way I want out of steel tubing and clamps.

 

[GoFastGus]

An old guy's advice for the college student: for reliable transport get another bike and install a mid drive like a Photon.

That’s an option I’d consider for a new bike. I’ll have to do some research on high power mid drive kits.

You can install it in an hour and it will do ~40 MPH if you need to and have a good enough battery. Lube the chain once in awhile and you are good to go. No issues changing flat tires. Then keep working this hub motor bike as your hobby or science project.

That’s a good point, they have some good reliability pros over hub motors. Do they come with upgraded chains for high power?

This is the same advice I give my brother who likes to buy old BMWs for his daily drivers

Bimmers are fun weekend cars (not my taste, I’d prefer a miata or classic Ford/GM), but yeah, not great daily transportation.

 

[E-HP]

How much above 50 have you not seen balance issues? This bike approaches 50mph on an open flat road

I’ve swapped tubes before, and all I’ve used is the tools to take the wheel off the bike (11 & 21mm sockets in the rear on this bike), tire levers, and a bike pump. Am I changing my tires incorrectly?

I just hit the throttle and let off when I decided it was too stupid to ride any faster wearing a bike helmet and windbreaker for protection. Dying on a ebike going 50mph has to one of the most pitiful ways to go. The Cycle Analyst logged 52.7, but it was still accelerating with field weakening on.
I mainly ride around at 20-25mph. The 5T has enough torque to wheelie at 20, just twisting the throttle, so you need to be extra careful if you pedal, and learn to lean forward out of habit. Im comfortable riding on streets with 25mph to 30mph speed limits, since there’s enough torque to zip up to 40 within a couple of seconds if I need to maneuver out of a situation. If you’re going to ride at ebike speeds, then a slow wind motor at higher voltage is a pretty fun combo.

I guess if you’re willing to carry the tools, and to go through the hassle to be fully protected, might as well do it.

 

[GoFastGus]

It is really worth switching to waterproof multi-contact connectors. XT60 / XT90 are excellent for power supply, especially if the motor is powerful. The contact is tight and they do not heat up.

Can XT60/90 connectors work for 3+ pin connectors, or are they only for 2 large gauge wires?

 

[99t4]

Why’s that? Is it a safety issue or something else?

(About the comment on not using wire nuts) Reliability and safety issue.

For house wiring, they're fine common acceptable proven practice. Usually the wires are clamped into a junction box (and also stapled to a framing stud near the box) so the wires are restrained from moving around, getting pulled, twisted, buffeted, etc.) If the wire nuts are torqued sufficiently to spec (most are not!) they hold the conductors together no problem.

Bike is a different environment. Vibration happens, wires get pulled, buffeted by the wind, bumps, shocks, etc. Tends to loosen the wirenuts leading to intermittent connections, overheated connections, and possible shorts.

Look what equipment is used in automotive and aviation wiring-- high quality crimped connections.

Some have successfully used Wago type clamping connectors for experimental wiring configurations on ebikes.

Can XT60/90 connectors work for 3+ pin connectors, or are they only for 2 large gauge wires?

Called the MT60, 3 pin connector in a triangle shape. Any more than 3 (at that size) and it starts to get real difficult to use, talking disconnect/connect here.

 

[GoFastGus]

Luckily We have BikeLink lockers around where I live

Update: so do I, thanks for the tip! Applied for a spot at my local one.

 

[GoFastGus]

Called the MT60, 3 pin connector in a triangle shape. Any more than 3 (at that size) and it starts to get real difficult to use, talking disconnect/connect here.

Thanks for the tip! Is that something I could use on a 3 phase lead motor with 12ga wire?

 

[99t4]

12ga is the upper limit I think. You can easily check for yourself. Lots of information on mt60 online. Even here on ES!

 

[raylo32]

CYC makes a fortified drivetrain with fewer and stronger rear cogs, compatible shifter and stronger chain. It isn't really necessary for Photon but might be a good idea if you got an X1 Pro Gen 4 with 72v and wanted to push it to the max. I believe this is only compatible with thru axle hubs but I am not sure. I run standard bicycle 8 and 9 speed drivetrains on my Photo gen 1 bike and X1 Pro Gen 2 bike. Not had any problems, but I am not pushing much more than 2Kw and then only for short throttle runs. I mostly run pedalec with their torque sensors and can easily ride along as fast as I need to go until I need to maybe merge with or cross auto traffic, then throttle up.

That’s a good point, they have some good reliability pros over hub motors. Do they come with upgraded chains for high power?

 

[Zambam]

For your next build, since you will be keeping it indoors to avoid theft, weight will be an issue. How heavy a bike can you comfortably haul up and down the stairs day in and day out?

What's your commute distance and terrain like? How fast do you really need to go? Pick the smallest/ lightest battery that will do the job. You also want a bike that's easily pedal-able home if you run out of juice.

 

[GoFastGus]

CYC makes a fortified drivetrain with fewer and stronger rear cogs, compatible shifter and stronger chain. It isn't really necessary for Photon but might be a good idea if you got an X1 Pro Gen 4 with 72v and wanted to push it to the max.

72V might be in store for the next build, so that upgraded drivetrain sounds worth looking into.

 

[GoFastGus]

For your next build, since you will be keeping it indoors to avoid theft, weight will be an issue. How heavy a bike can you comfortably haul up and down the stairs day in and day out?

Good point. Not fully decided between bike locker & storing somewhere in my building, so weight up & down stairs might well be an issue.

What's your commute distance and terrain like? How fast do you really need to go? Pick the smallest/ lightest battery that will do the job. You also want a bike that's easily pedal-able home if you run out of juice.

All good factors to consider. It's difficult not to get scope creep when planning a build out on paper, but I need to remember that this bike needs to also work with my daily life and can't be an impractical hassle.

 

[GoFastGus]

12ga is the upper limit I think. You can easily check for yourself. Lots of information on mt60 online. Even here on ES!

I appreciate how politely you told me "use the search bar, noob!" I'll add that to my reading list, thanks for all the advice!