What I didn’t know about electric bikes

After a lot of research this weekend, I learned quite a bit more about electric bikes and how they work.  I particularly concentrated on how the motor in the rear hub operates and how it can provide power without any moving parts.  My first goal from this point will be to open the hub shell of an Ultra Motor brand hub motor in the rear wheel of a Stromer.  I’ll detail all of it in a well-covered post.

Most of the information I found was on just a couple websites which I somehow had not come across yet. Electric Bike is definitely well organized and provided the most information about a variety of hub motors and their corresponding controllers and diagnostic procedures.  Ypedal has an amazing and vast knowledge of the systems and has created tons of custom setups as well as details repair on several Youtube videos that is a complete procedure and well explained.

Most of the motors have a similar layout:  An outer shell to protect and encase the motor, then a ring of magnets that are positioned between the shell and coils of copper wire.  Other than a couple sensors and wires that exit through the center of the wheel near the axle, that’s about it.  Very simple and once familiar with the parts, moderately easy to work on.  I chose to first learn about the motor because it seems like this is the only component that I haven’t been able to service other than to simply install a replacement wheel.  To have the ability to fix the motors once the manufacturer’s warranty expires will be essential — especially as the number of electric bikes is increasing and they are becoming more common.

Back to the sensors and wires in the motor.  Usually there are three small square shaped sensors that are positioned between two of the outer magnets in line with each other.  These are called Hall sensors and they measure the electrical current coming out of the motor as the wheel spins.  A tapered side of the sensor body is always positioned outward and usually is set with a tiny amount of JB Weld or epoxy. Out of the top of each sensor are three uncovered wire leads that are soldered to colored wires carefully running to the center of the hub and exit from the wheel to the controller and potentially a torque sensor.  A torque sensor is generally on higher end electric bikes while cheaper versions simply use a cadence magnet to calculate the input of added power.  The torque sensor is nicer because it adds power based on a direct measurement of the deflection of the wheel backward against the rear dropout when you put pressure on the chain and pedals.  Most are robust and work accurately, giving the rider a better feel of added power when accelerating.

In some situations, I read that one or more of the Hall sensors can go bad and with the right tools, it is a small project for an afternoon that will avoid a replacement ($500-750) or service elsewhere ($100/hr).  Even if you aren’t up to doing the task yourself, you will be better able to diagnose and familiarize issues that occur.  For the avid mechanic, it is possible to upgrade your hub motor for minimal cost.  Larger wires (if they can fit through the frame and center of the wheel) will boost available power and a better controller or throttle can more accurately distribute the power.  Unless you have an extreme desire to mod your electric bike, the magnets and copper wire are difficult and costly to replace.  Some motors are spun low with larger gauge copper wire which can provide more power, but less torque on hilly terrain while high spin copper will have better power at a high cadence and will last longer.

In order to remove the motor from its hub shell, a car bearing puller is necessary.  It is an extractor style tool with three arms that pull on the shell while a center bolt pushes the axle and opposite hub shell side.  It is helpful and recommended that you tap the shell with a mallet during this process to aid in freeing the two halves.  Otherwise, direct extraction with the bearing puller could break the hub flange and then you’ll be left with a useless motor and no shell.

Considering the Stromer that was detailed in the review and diagnosis, I believe that the torque sensor was overloaded in the frame without that necessary bolt and the motor overheated and fried one or more of the sensors.  This would explain the NO_COMM lack of communication between the LCD controller and the motor.

It makes a lot of sense once the elements are broken down like that.  I also think that one of the wires exiting the rear hub is a faulty wire with a weak spot somewhere near the center of the wheel.  The torque sensor itself seems okay.  I am going to check current through each of the wires to determine the faulty one and then solder in a new one along with the replacement of the sensors.

I was very happy to find this information and come to realization that these bikes can be fixed from the ground up if necessary.  Why wait a week or weeks for new parts to install when the local hardware store and Radio Shack have all the necessary parts for a solution?  I am going to continue to do more research into the motor repairs as well as connecting different controllers to the bike for operation.  It is exciting to realize that with the right research, I can create incredibly fun bikes that are useful for both fun and transportation. Now, once I can locate a car bearing puller, I’ll open the motor and take photos of everything so you can see it.  Stay tuned!

– SNC

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How To Properly Glue A Tubular Tire

I am sure that many people have great techniques (as well as poor ones) on how to glue tubulars, but I thought I would provide my take on it.  I have glued well over 500 in my career thus far and not one has ever come back where it “rolled” off the rim.  I take this as a good technique proven over time because if it is one thing I can pretty much guarantee, it’s that someone who rolls one will definitely make sure the ‘gluer’ knows that it happened.  If you perfect the consistency of your method while gluing, then you will have predictable results that are positive.

That being said, let’s dig in.  If you are a bike shop mechanic and haven’t tried gluing, practice on a set of ones first and have them inspected about a week later by someone who has glued.  If the tire is quite difficult to pull off, then you’ve done it right.  Recently, I have come across several cases where a poor gluing was easily reflected in the difficulty (or ease) of pulling the old tire off.  Either the glue had been applied in spots on the rim or almost none at all in the center.  Let me express that you don’t have to have glued a ton of tubulars to get it right.  You just have to follow a method that is proven and makes sense.  If you are a cyclist that doesn’t have access to a shop, then follow this guide because you’ll know your wheels better because of it and you’ll always have the opportunity to be race-ready.  The process can be done in a day with the right tubulars or over several days for ultimate quality and aesthetics.

The first thing I do is to obviously remove the old tubular.  If it has been glued correctly, this will be the second hardest part.  Below you will see a series of photos detailing the removal.  I usually start by taking my index fingers and thumbs and rock the tire side to side in different places on the rim to try to peel the edges of the tire off.  If a particular section starts to peel well, I will focus there.  I take a plastic tire lever and run its edge along the part of the tire that is glued.  This kind of ‘cuts’ the glue to start the removal and ensures that the base tape does not rip off the rest of the tire.  Then, I begin to pry the edge of the lever under the center of the tire until it gives way to the opposite side.  Push either forwards or backwards along the rim flexing the lever upwards to peel more of the tire off.  Once you’ve done this for about a quarter of the radius of the rim, take the lever out and use your hands to peel the rest of the tire off.  Then, put the wheel in a truing stand if you have one for inspection.  Here are the photos of me removing a Vittoria Corsa Evo off of some Campagnolo Bora Ultimates.

After peeling the tire off, inspect it and compare the base tape to the new tubular being glued.  Many times, indentations around each rim hole for the spoke nipple will be seen.  Glue that is hastily applied will seep into these holes in the rim and create havoc for future truing and for broken spoke nipples to exit the rim in a spoke replacement.  Note any areas that are lacking in glue.  More importantly that this is to check the rim bed (the area where the tire contacts the rim) for leftover glue and any inconsistencies.  Check these two photos out:

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In the left photo, you can see that glue never really even made it to the right side of the rim and the indent in the center of the rim bed holds roughly the same thickness of glue as the left side.  From a better perspective, the right photo shows the area on the rim I found when peeling the tubular.  My best guess is that a layer of glue was on the tire and then a bead of glue was drawn onto the center of the rim bed before mounting it.  Don’t ever use this method.  That tire is not secure at all for racing — much less around the parking lot for a test ride.  I recommend at this point to mark non-glued tubulars on display models with a symbol on the valve extender with a silver Sharpie marker.

This is how to glue the new tubular.

Since there was little glue on the rim to start with, I elected to ‘paint’ over the existing glue using Vittoria Mastik One tubular glue.  It is rated the best — it holds the best (I have heard recently of using this in conjunction with gluing tape for cross tubulars and the methods I was described sounded great and sound).  The first step is to start spreading glue on the tubular since the base tape will soak up the first layer.  I like to focus on getting about 95% of the base tape covered in a nice layer of glue.  This means no thick spots or globs.  Use an acid brush (hardware stores — very cheap and perfect for the job) to steadily spread the glue in long sections several inches at a time with short strokes.  I usually spread a bead of glue (as pictured below) around a sixth to a quarter of the circumference at a time.  This helps to ensure that the glue doesn’t begin to thicken and dry or drip down onto the rubber of the tire.  While a little glue may touch the rubber, a lot is difficult to fix and results in poor treatment of the rubber to clean.  Take your time and be thorough.  Each coat takes about 10-15 minutes for a beginner and about 5-7 minutes once acquainted.  Check out the progress below.

One important thing to note with layers of glue on the tire is that you want to build a little extra glue right around the valve where it meets the base tape.  This will help prevent damage from pumping it up as well as rough valve holes and a secure fitting when stretching onto the rim.  Like this.

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Next is the rim.  I apply glue the exact same way as the tire.  Do two coats on the tire and two coats on the rim.  Spread it evenly and take care to both cover rim edges around the spoke drillings and the areas between.  Spread 2-3 small half-dime size dots of glue between each spoke drilling approximately a quarter way around the rim at a time.  Start at the last place you dripped glue and spread upwards in directional slow strokes.  Angle the brush to drag excesses of glue along the rim to areas where application didn’t sufficiently cover.  The speed of this process is a lot of what experience will give you.  The more you do, the quicker and more efficient you will become.  The idea here is that you follow the steps precisely so that you get glue where it should be.   The aesthetics will come with time.  Tubulars that stay on the rim are always cooler than pretty ones that don’t.  Here is the glue process.

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You can see in the right the bead drops of glue and spreading them out in the left photo.  Let each layer dry completely to touch and then it will be time to mount the tire onto the rim.

Take the tire and apply a very very thin layer of glue over the middle 70% of the basetape.  This will aid in activating the glue on the rim and in allowing a bit of positioning.  Check the tread and make absolutely sure that you will be stretching it on the correct direction.  Nothing is more terrible than realizing you just put the tire on backwards. Check the tread one more time.

Insert the valve into the valve hole with only some ‘pliable pressure’ in the tire.  You should be able to stretch it with moderate effort.  Begin with a hand on each side of the valve and pull the tire away from the valve in the direction of the rim.  Check the base tape on each side to make sure it is being placed evenly along the rim.  Once you get to the final six inches of the tire, wedge the axle of the wheel against something and pinch the tire while pulling it onto the rim.  Some cases and combinations of tubulars and rims are exceptionally difficult and some are wonderfully easy.  Vittoria happens to be a tubular that rides incredibly well and stretches easily onto almost any rim.

I hope this helped clear up the process of the gluing.  I may extend the article soon and include some photos of actually stretching the tire.  Feel free to comment and suggest any methods that are well proven.  Thanks for reading!

– SNC

Basic Wheel Truing and Tensioning

Wheels are perhaps one of the most complex parts of cycling in that they are the contact between the rider and the ground or pavement and can be considered the best upgrade a bicycle can have.  Properly trued and tensioned wheels at all levels greatly improve the quality of the ride and the longevity of their peak performance.  Attention to detail, patience, and practice will provide you with worry free operation time and time again.  In the rest of the article, I’ll be referring the true and tension of a wheel as simply wheel truing because both are necessary to keep a wheel straight and rolling correctly.

I believe that anyone can true their own wheels (except for some tubulars and several specific racing wheels) with a bit of guidance and attention to detail.  Taking the time to check your wheels after long rides and on a regular basis will allow you to minimize the amount of truing needed.  A wheel can only be trued so many times before there are no more threads left to tighten on the spokes.  Below is a diagram of a section of rim, a spoke, and a spoke nipple.

Components of Wheel

In this diagram, the spoke is threaded into the spoke nipple, which is anchored by the small lip on the inside of the rim. There are about 10mm of threads on the majority of spokes. Usually, 5-8mm of threads are threaded into the spoke nipple, based on correct spoke length calculation.  This leaves several millimeters of thread to be tightened during the life of the rim and spokes for truing.

Tightening the spoke nipple will guide and pull the rim to the left or right laterally as well as pull it inward towards the hub.  A diagram below illustrates this.

Cross Section of WheelIn this diagram, several of the elements were recreated from the first diagram (the spoke, spoke nipple, and rim).  This is a cross-section of the rim to show how tightening and loosening the spokes will cause the rim to move to the right or left.  Notice that the spoke and spoke nipple does not anchor to the rim at a direction 90 degrees, but at an angle because of the fact that the hub (the center part of the wheel) is wider than the rim.  If you tighten the spoke from the spoke nipple in this diagram, the rim will be pulled to the left.  If you loosen the spoke from the spoke nipple, the rim will move to the right.  This is how, over the course of the rim and all the spokes, that the rim can be straightened and thus, trued.

Now that the concepts are a little clearer, we can then focus on how much to tighten and loosen the spokes.  Once a wheel is built the tension of all the spokes should be relatively even.  Factory built wheels tighten all spokes to a specific tension, causing the rim to usually be slightly out of true once it gets to the shop from a distributor.  The reason that the rim is not true from every spoke being at the exact same tension is because of all the variables in the wheel add up and even high quality parts have small imperfections and variations in machining and manufacturing, summarized by the term, tolerance.  Remember that term because it will come up later.

When truing a wheel, it is wise to make small adjustments each time until the rim is straight (1/8th turns to 1/2 turns).  Never just crank down on one spoke and tighten it until the rim straightens.  This will cause uneven tension of the wheel, which will lead to spokes breaking and the rim to develop a ‘set’ and a shorter lifespan.  Spin the wheel and notice how much the rim moves side to side and settle on the worst sections first.  If you see the rim move to the left or right over a section, take note of how many spokes pass throughout the bend.  Find the worst part of the bend and tighten that spoke about a half turn and then the spokes on either side coming from the same side of the hub.  Tighten those spoke less and less the farther it gets from the spoke you first tightened a half turn, tightening less as the bend recedes.  Lightly squeeze spokes with your hands and spin the wheel in between truing to settle the adjustments.  This ‘shares the load’ between the spokes to straighten that section of the rim and allows the tensions to be gradually increased.  The spokes in a wheel do not work individually as much as being a team.  All must help to share the load of the rider on a bike.

Earlier I mentioned that spokes could also be loosened.  This is only really acceptable in very small amounts and as a second option after tightening spokes.  Loosening decreases tension in the wheel, which can also lead to spokes breaking and less threads engaged in the spoke nipple.  In particularly difficult sections of a rim, tightening and loosening is used to correct a bend, but only with practice and experience over time.  Even with this basic tutorial to help you better understand how a wheel is trued, your first few wheel truings will be a little frustrating.  Know that as you progress and true more wheels, you will begin to understand how much you must tighten a section of spokes to eliminate bends in the rim.  Lastly, sharp bends in a rim are nearly incurable and you will notice that one or two spokes must be tightened by a large amount to even get the wheel ‘mostly’ true.  If this is the case, the rim may need to be replaced and new spokes.  The spoke itself is very very strong and can easily hold 300lbs hanging from its end without much wear.  This being said, the spoke’s main enemy is uneven tension and the fact that there are only so many threads on the spoke’s end to tighten.

In summary, remember these two things.  No spoke works alone and thus, tighten groups of spokes to share the load small increments at a time.  The tolerance of machines and production allow a wheel to be only so true.  Low quality wheels can be trued to moderate expectation and high quality wheels can be trued to high expectation.  This is the difference in tolerances of machining.

Feel free to email or message me regarding any questions you might have.  People have written many books on this subject and I could continually talk to you about wheel theory all day.  Hopefully this article will help you to better understand wheels, how they are adjusted, and your confidence in being your own bicycle mechanic.  Thanks for reading.  Monday night, I’ll be posting Part One of the Specialized Turbo S Long Term Review and what things I have come to learn about working on them, adjusting the electronics, and general knowledge as far as how the technology is progressing.

 

– SNC

 

Wheel Truing and Specialized Turbo Long Term Review

I will be posting a short article tomorrow evening on wheel truing and will also post Part 1 of all the info and tuning/adjustments I have been through and discovered with the Specialized Turbo S Pedelec bike. I look forward to your thoughts!  Stay tuned for for great info and photos.

P.S.  I also edited the Dura-Ace 9000 front derailleur setup article after reviewing a few comments from readers and my own experiences with the setup.

 

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– SNC