first build - 30X4.5" tire FWD snow bike

[rocwandrer]

The bike:

A few years ago I built this bike frame from high grade steel tubing and bronze joining filler:

I'm around 6'3" (191cm) tall, so the proportions of the bike look about right in pictures. For comparison, a photo of the rear tire beside an aggressive off road 26X2.4:

The front fork is 135mm spaced and centered, fitted for a rear disc brake caliper. The rear is 135mm spaced, 20.5mm offset to the drive side. This makes it so the chain can clear the tire with 6 speeds on 9 speed spacing, and I can still run any standard 135mm spaced hub.

 

[rocwandrer]

Discharge log with lots of boring commentary mainly put here for me to keep my memory honest (edit: have confirmed these are Turnigy 4500 mah 6s2p LiFePo4 packs, not sure why the label was partially torn off and a sticker placed on them saying "4.4 ah"):

Controller shunt shaved. Can deliver 17 amps at stall, but the noise from the motor stops me from ever doing that. On steep hills at low speed, it will put out 10-13 amps for a few seconds. In practice, I run these between 0-8 amps ~99% of the time, with an average of 2-4 amps over the course of a typical trip. at reasonable speeds, it wont deliver more than 8 amps, and drops off slowly with increasing speed.

1 - unknown top off from storage condition
2 - 1.30 ah (RT=round trip)
3 - 3.75 ah (RT plus, around 300 mah to balance)
4 - 3.42 ah (RT)
5 - 2.16 ah (RT)
6 - 1.84 ah (OW =one way, to work, 100% throttle the entire way, cell 4 lower than the rest, cell 5 higher than the rest. Not sure which pack is driving this, both seem high on cell 5, even with separate charging)
7 - 2.10 ah (RT, moved charger to at work, -10F ambient temp, 3.33v just before charging, surface charge holding for longer now, 1.5 hours after balancing to 3.65v the cells are at 3.55v, except 5 in both packs at 3.58v)
8 - 2.82 ah (RT)
9 - 1.15 ah (RT, through the woods over packed/heat treated snow, took 90 mah to balance)
10 - 2.43 ah (RT, long way through the woods in the snow both ways)
11 - 2.08 ah (RT, pavement, almost hit by falling trees 4 times on the ride in (once was endo provokingly close)
12 - 2.18 ah (RT, balanced to 3.41v on the lowest cell, 3.65 on the highest)
13 - 2.60 ah (RT, 130 mah net to get back to 3.42v in balance charging, 200 mah to get to 3.6v/cell. 95% throttle setting with substantial pedaling both ways. 100% throttle yields too low an effort or too high a cadence. resting voltage of 3.38v implies a balance charging voltage of around 4.42v )
14 - 3.11 ah (RT)
15 - 0.63 ah (OW, tested out new used bulk charger briefly)
16 - 2.00 ah (OW, 400 mah to balancethrough the woods and on pavement. Found out that 150 w input or approximately 100 w to the ground of assist seems to be the point where it feels worth having the assist. 50 w input to the controller is the point at which there is something other than noise noticeably coming out of the motor. It only costs 4w to have the controller on, and about 30w to have the motor turning but not driving the wheel, seemingly regardless of speed. 500w of input to the controller at low to moderate speed seems to generate substantially less acceleration from the motor than I can produce myself at a "couple minutes" exertion level. Seems about matched at high speed.)
17 -1.1 ah (didn't charge, OW so far)
car pool - rebuilding front wheel
17 - 1.97 ah charged. Charge stopped at 42.06v, then took 128 mah to balance.
18 - 2.34 ah measured with iMAX B6. 0.75 ah to get home measured with watt meter; this is under 10wh/mi and the assist was perfect. Didn't feel like I was using assist much, but got up the hills quicker without knee pain. 1.29 ah to get in, 1.4 after leaving the watt meter on and the controller connected for a while. 2.34 ah total indicated delivered charge on the iMAX B6. 88 mah 12s to balance. 41.7v before balancing.
19 - 2.13 ah (0.9 ah of this was at ~25F with the pack starting out cold, all other discharges have been with battery starting warm in an insulated space with the controller) the charge roughly matches the discharge ah) 70 mah balance to 3.45v
20 - 2.31 ah
21 - 2.20 ah
22 - 3.25 ah
23 - 2.45 ah
24 - 2.80 ah
25 - 2.91 ah 174mah to balance
26 - 2.08 ah
27 - 2.86 ah + 150mah to 3.45v, +20 mah to 3.6v
28 - 1.89 ah
29 - 3.18 ah, discharge from starting warm, insulated, and not too cold out 3.033 ah recorded on the ah meter. 203 mah to balance
30 - 2.8
31-59 ~2.6 ah each 4/19/13 update. My use has stabilized and I'm on track for about 19 days per month doing 2.6 ah a day. Will update if this changes.
60 ~____ 10/25/13, back riding the bike. Cell voltages matched after 6 months of sitting around at ~75%SOC. Used 0.5 Ah and cells were down to 3.32v, so there couldn't have been much self discharge over the course of 6 months.

~72 - 2.950 ah 0.3 ah balance. Before charging, 3 cell pairs out of 12 were around 3.11-3.12v, with the other 9 between 3.22 and 3.25v.

Subjectively, voltage sag under load is much greater. A fresh pack used to sag to around 38v going up the first steep hill on my commute. Now it is more like 36v. Packs start the trip at room temp and don't have much time to cool before the hill, so it isn't the weather. 4/9/14

 

[Teh Stork]

Knee problems are often a result of weak glutes. Deadlift twice a week and start the day with glute activation excersices and your knees will be better in no time

 

[Drunkskunk]

Glad to hear the kid is ok.
You'll love that Fat bike with a motor. I've had mine going for a couple months now and I haven't even touched my other Ebikes. I bet you'll find you don't take the motor off, even if you just go out to pedal it.

 

[rocwandrer]

Why build it:

If my username looks familiar, I started working on an electric assist last year around this time, and then we found out that my daughter needed heart surgery. Skipping ahead a year, all is well with her now, and I'm back around to knee pain on uphills in the cold weather. I'm looking for a little assist to keep me riding my bike to work through the winter. I've been riding to work for 10 years now. My commute is only 3 miles using the shortest route, which is the way I take when my knees hurt. I fully intend to remove part of the electric assist from this bike for regular use, and put it back on for commuting.

A secondary reason for the assist is to be able to take this bike (instead of a faster road bike, or a car) on days when I am running late or the weather is bad (adding rolling resistance, slowing me down), and still be able to get in an off road ride on the way home.

If this hobby gets its claws into me like you folks, I'll build more later, but this build is going to stay modular/detachable/low powered/cheap-ish.

The assist kit - stuff I think I have figured out and have ordered:

Front wheel: Cute Q100, 36v, "201 rpm", disc compatible, 135mm axle spacing laced to a 559x100 double walled rim. The plan is 2 cross, with the left side spokes going to the right side of the rim and so on to give a decent brace angle without having to redrill the rim like I did in the rear. This also gives more clearance for the caliper on the 203mm rotor.

Rear wheel: XT freehub, custom assembled 6 speed 14-32 cassette 9 speed spaced (visible in the second photo in this thread), with 9 speed chain.

controller: KU63 with KU123 ordered as a backup. I will probably mod the KU63 for somewhere around 9-11 amps.

Batteries: 2x Turnigy 4500mAh 6S2P 30C LiFePo4 Packs

 

[rocwandrer]

Knee problems are often a result of weak glutes. Deadlift twice a week and start the day with glute activation excersices and your knees will be better in no time

With the knee replacements in my family, and this problem steadily getting worse with age, seemingly without regard for what shape I'm in, I don't hold out much hope for that. That said, I googled glute activation exercises, and find that my situation resembles the typical person they target. I'll try it out. Thanks!

 

[rocwandrer]

Glad to hear the kid is ok.
You'll love that Fat bike with a motor. I've had mine going for a couple months now and I haven't even touched my other Ebikes. I bet you'll find you don't take the motor off, even if you just go out to pedal it.

Thanks! The plan is to remove most all the Ebike stuff for weekend riding, and take as much as is quick release off for weekday unassisted recreational rides (which often happen right from work, and I ride home after.) I need to take enough off so it is obvious I'm not using the motor in order to fit in on group rides, unfortunately. I'm lazy though, so it would be good to know if the Q100 axle and bearings are up to some winter offroading. I figure it has to help that I'm running a rear axle size in the front.

What do you have for a fatbike? What's the setup?

 

[rocwandrer]

I typed all this together, but then decided to split it up in to more manageable chunks...

Stuff that is still up in the air / specifically looking for input on (1):

charger: IMAX B6. Can I mount this to my controller/battery box and take it along, or will it not hold up and I should have bought another one? Since I think I already know the answer to the last question, what's a cheap bulk charger I can use at home? I'm thinking 50W would work, but 75w would be better.

Battery protections:

1.) LV cut on controller is about 2.2v/cell. Does this seem a little low?
2.) Separate low voltage alarm cell checker set to somewhere between it's minimum of 2.7v and maybe 3.0v. What is a good starting point for 2.5c on LiFePo4 if I want to try to target 20% SoC as a minimum?
3.) Watt meter and good judgement about time and usage. I'll time some charges to get an idea of the depth of charge I'm using under different conditions.
4.) I plan to bundle the 2 packs in with the controller without airflow, and then insulate them further inside a pannier. I plan to store this at room temp for at least a few hours before each use. I can take temp readings and see if this is too much or not enough. I expect ambient temps to be around 0-35F most days, and the trips to last only 10-20 minutes, so I figure with a reasonable starting temp, most anything will work.
5.) I'll only charge when the cells are at room temp, and charge at 0.2-0.5c.

 

[rocwandrer]

Stuff that is still up in the air / specifically looking for input on (2):

Throttle:

I did some searching here, and came up empty. I know it must have been discussed before. I like SRAM trigger shifters, and run old servowave brake levers (awesome with cable discs!) I don't really even want the throttle on the bars when I'm not using the assist setup, so I didn't get a twist grip throttle. I bought a thumb throttle, thinking I can figure out a mount that is quick-release that somehow either puts the throttle within reach, or is friction only without a return spring maybe? Thoughts/suggestions/links to old threads here?

My other thought is that maybe I mount the 3-speed switch on the bar, and set it up as a binary throttle. I could set the throttle position inside the pannier, and then have on or off via a switch on the bars. This is only about 200w assist, so I think that might be ok. Can I put maybe something like a capacitor across the throttle signal line, to reduce shock in the gears on the hub when going from moving throttle off to moving throttle on, or is that even necessary?

 

[Drunkskunk]

What do you have for a fatbike? What's the setup?

Well, its a hand built frame as well, but I think I went the opposite direction from your setup.
4" Surly Larry tires, 55 inch wheelbase, Full suspension frame. 5404 motor that will put out over 10,000 watts. Its a bit of a monster.

 

[rocwandrer]

What do you have for a fatbike? What's the setup?

Well, its a hand built frame as well, but I think I went the opposite direction from your setup.
4" Surly Larry tires, 55 inch wheelbase, Full suspension frame. 5404 motor that will put out over 10,000 watts. Its a bit of a monster.

That thing is a monster! The frame design looks like an elegant solution for your intended goals (if you started out planning for over 12 hp of output )

Does it have frame and fork clearance for bud and lou?

 

[rocwandrer]

Wiring:

Battery:

My plan is to wire the two batteries into a the A side of a 4-flat boat trailer wiring extension cable.

This plug is polarized with an A side and a B side, is good for plenty of amps, and will handle a lot of connect/disconnect cycles. With dielectric grease, they hold up the elements reasonably well, and this one will live in a pannier. Even better, there is at least one on the shelf in my garage right now.

I'll make a patch cable to wire the charging leads on the charger to a B side plug in parallel configuration.

I'll use a parallel balance lead, semi-permanently attached to the charger.

For charging, I'll have 3 connections to make (two interchangeable balance leads, these are polarized, right?) and a 4-flat. For discharging, I'll have only one, impossible to mess up connection to make, and maybe a switch to turn on.

Controller

I'll wire the controller power leads from the battery such that it puts the two batteries in series on the B side of the connection, with an additional connection for the on/off lead (will it hurt the controller to leave this lead hot all the time, or just damage the battery connections over time?) I'm also thinking of switching the 4-flat to 5 flat, and shortening the barrel on the 5th terminal so it makes electrical contact after the other 4, then using it as the power up lead on the controller.

I'm assuming that the motor connection between the patch cable that comes with the motor and the controller is plug and play, and the same with the 3-speed switch and throttle.

Did I go horribly awry anywhere there?

Given that I'm going to be riding in sand/salt/snow/rain, should I pull the motor apart and spray it down with corrosion-x or boeshield T-9 or something like that?

 

[dogman dan]

A couple obvious red flags.

One is don't carry the charger. Put the charger in a fire resistant place, and make your battery easily removed to take to said place. Same for storing the battery, store em in a place where a fire won't ingite the whole house. Steel boxes kind of stuff, but not completely airtight ones, that would fail and vent sudden.

A B6 is a decent entry level charger, but it will be painfully slow at 50w. 4 hours for just two lipo bricks. You can't put lipo on charge, then go to sleep, leave the house, etc!!!!!! So you might like a 150w or 200w charger a lot better, aiming for closer to 1 hour charging.

Forget those trailer bullets for the battery wires. Get some decent 12g silicone wire, and some anderson connectors or some 4mm bullets. In the USA powerwerks for the andersons. EP buddy is a decent place to buy some connectors and wires, and maybe even the charger.

Leave the motor on the bike all the time. You'll strip out the axle for sure if you bolt it on and take it back off enough times. The threads are not german quality on that axle. Happliy, you chose a pretty light motor with an internal freewheel, so pedaling with the motor still on the bike will not be so hard. Bet those fat tires drag enough already to make it somewhat the same feel with the motor on the bike anyway. No reason not to make the controller and battery easy to remove from the bike. Some kind of box that contains the battery, and has the controller bolted to the box might work fine. Personally though, I'd just leave the controller in place too, and just remove the battery for the weekend rides. Well, truthfully, I'd just ride the bike powered all the time, and just call myself a cheater on the group rides. Use your knees for an excuse.

As for the knees, I'm no doctor, but every time I pulled my knee loose pedaling to hard on single track trails, I healed it best by lots of long rides with just moderate pedaling on the ebike. If something is slightly torn, you definitely want to heal it moving, but not re tear it every weekend. A GOOD REASON TO JUST MOTOR IT ON THOSE WEEKEND RIDES.

Get a cellog 8. It's just a really handy tool to have in your kit, even carry in your pocket while riding. Makes looking at battery voltage a snap. While riding, some kind of whole pack voltage meter is a must. Doesn't have to be a cycleanalyst, but they sure are nice!

 

[rocwandrer]

A couple obvious red flags.

Good! That's why I posted all this, though i probably should have stretched it out over a few days

One is don't carry the charger. Put the charger in a fire resistant place, and make your battery easily removed to take to said place. Same for storing the battery, store em in a place where a fire won't ingite the whole house. Steel boxes kind of stuff, but not completely airtight ones, that would fail and vent sudden.

A B6 is a decent entry level charger, but it will be painfully slow at 50w. 4 hours for just two lipo bricks. You can't put lipo on charge, then go to sleep, leave the house, etc!!!!!! So you might like a 150w or 200w charger a lot better, aiming for closer to 1 hour charging.

Don't carry the charger. Check. Painfully slow. Check. Fits right in with my day at work. What is a good dirt cheap 100w-150w bulk charger to have at home?

Fire resistant place... I bought LiFePo4 which I plan to seal up in carbon composite or aluminum skins. I was planning to charge in a metal cake pan, on or under my metal desk at work. I sit at a desk for 8 hours or so out of a typical 10 hour day, so I figured a 2-4 hour (not planning to run them dead all the time) charge is no big deal and I can babysit them. I work at a place that is VERY pro-electric transportation (we have outlets out front just in case anyone with a plug in hybrid shows up), so I could probably secure some 8 ft thick concrete lab floor well removed from flammables and near an outlet, if I had to. I'm not convinced I need to be that conservative here.

Forget those trailer bullets for the battery wires. Get some decent 12g silicone wire, and some anderson connectors or some 4mm bullets. In the USA powerwerks for the andersons. EP buddy is a decent place to buy some connectors and wires, and maybe even the charger.

Why? My thinking on the trailer wiring plugs is they will handle all the current a 12g wire will handle, and it is a fail safe against wrong polarity/series-parallel errors, etc. What is the reason for not liking the boat trailer wiring plug? Why are the other choices better? I bought all the connectors I need to do the whole thing with 4mm bullets, but thought the multiple lead, single plug concept is good for idiot proofing/simplifying.

 

[rocwandrer]

Leave the motor on the bike all the time. You'll strip out the axle for sure if you bolt it on and take it back off enough times. The threads are not german quality on that axle.

A good point. I might try to find some bronze nuts to use, to help with this, and/or copper anti-seize. Doesn't really matter now, laziness just got the excuse it needs to leave the wheel in place all the time

Bet those fat tires drag enough already to make it somewhat the same feel with the motor on the bike anyway.

Actually, for 90% of the miles I ride the bike, the big fat, low pressure tires drag LESS than a more normal sized tire. Check out the roots in the first photo in this thread. These tires roll over those the same as a road bike tire rolls over cracks in the pavement. In the winter, even when it is less effort to cut through loose snow with a skinny tire, it is near impossible to steer accurately enough to keep the bike upright, where the big fat tires let you keep going as long as you can keep pedaling. They do suck mightily on pavement or smooth dirt road though, yes.

Personally though, I'd just leave the controller in place too, and just remove the battery for the weekend rides. Well, truthfully, I'd just ride the bike powered all the time, and just call myself a cheater on the group rides. Use your knees for an excuse.

As for the knees, I'm no doctor, but every time I pulled my knee loose pedaling to hard on single track trails, I healed it best by lots of long rides with just moderate pedaling on the ebike. If something is slightly torn, you definitely want to heal it moving, but not re tear it every weekend. A GOOD REASON TO JUST MOTOR IT ON THOSE WEEKEND RIDES.

The places I like to ride, the fat tires already give me such a big advantage that I already get labeled a cheater No need to sell me on the electric assist. If I like it as you say I will, I'll do what you suggest as a matter of course. I don't think I will, but we'll find out soon enough

Get a cellog 8. It's just a really handy tool to have in your kit, even carry in your pocket while riding. Makes looking at battery voltage a snap. While riding, some kind of whole pack voltage meter is a must. Doesn't have to be a cycleanalyst, but they sure are nice!

I spent $33.55 shipped for the ability to:

1.) see instantaneous watts/amps/volts display while riding if I want to.
2.) have low voltage auditory alarm on all 12 cells while riding, all the time.
3.) have 3 independent devices to check individual cell voltages, one of which displays 6 at a time. I thought this was important, given how low quality all this stuff is.

You say carry in your pocket... The only thing the cellog8 would give me that I don't have coming in my present order is voltage logging. Was that the reason you said cellog8, or is it more accurate than the other devices like the cell checkers and watt meter I bought?

 

[rocwandrer]

Motor and controllers got here yesterday. Batteries, etc just got sent to the airport in HK.

 

[maydaverave]

Great bike. Do you have any close up pics of your frame? I would love to see the brazing.

 

[rocwandrer]

Great bike. Do you have any close up pics of your frame? I would love to see the brazing.

I don't really have any closeup shots of the frame. This is the best I can find for closeup (crop and zoom didn't turn out so well because it was resized from the original).

It isn't exactly pretty anyway. My brazing is.... functional.... This was frame number 14, and I've had no frame failures in the last 14 years (I had some stick welded recumbents that ended badly early on). I can braze well enough now that I don't have to use super thick BB or HT stock, and still don't need any post joining machining. For pretty stuff, there is a lot out there on frame building forums, like the one over on MTBR.com. For example, pretty much anything by Dave Bohm is beautiful without any cleanup.

 

[rocwandrer]

I do have some slightly better shots of another bike I built:

the pictures I had on my work computer, uploaded here:

https://picasaweb.google.com/101738...&authkey=Gv1sRgCMCBpJ_JjbnWRQ&feat=directlink

 

[docnjoj]

That is really pretty! Thanks for the great work!
otherDoc

 

[rocwandrer]

That is really pretty! Thanks for the great work!
otherDoc

Thanks!

 

[rocwandrer]

So it appears "SpeedPost" lost my Hobby King order. I get to wait a month for my refund, unless "SpeedPost" admits to losing it before that time is up.

If I wait a month for my refund, and then order something else, the critical time I wanted the assist will be over by the time I have it working.

Any ideas on an interim solution? I could make use of as little as 100wh of capacity, but would need a charger too.

 

[maydaverave]

Seems a shame to paint those frames. I would polish them and then clear coat them raw. Thats awesome that you can build frames like that, I brazed in welding class and was impressed by the strength of it. Do you need oxy acetylene or can you get away with mapp gas? Going to have to learn more about this, thanks for the inspiration 8)

 

[motomech]

The assist kit - stuff I think I have figured out and have ordered:

Front wheel: Cute Q100, 36v, "201 rpm", disc compatible, 135mm axle spacing laced to a 559x100 double walled rim. The plan is 2 cross, with the left side spokes going to the right side of the rim and so on to give a decent brace angle without having to redrill the rim like I did in the rear. This also gives more clearance for the caliper on the 203mm rotor.

Rear wheel: XT freehub, custom assembled 6 speed 14-32 cassette 9 speed spaced (visible in the second photo in this thread), with 9 speed chain.

controller: KU63 with KU123 ordered as a backup. I will probably mod the KU63 for somewhere around 9-11 amps.

Batteries: 2x Turnigy 4500mAh 6S2P 30C LiFePo4 Packs

controller: KU63 with KU123 ordered as a backup. I will probably mod the KU63 for somewhere around 9-11 amps

The Q100/KU-63 combo will produce around 12 Amps stock. D8veh, myself and others have fornd 15 to 17 Amps to be the "sweet spot".
Above those limits, the Cute gets "growly", at or below, it is almost dead silent.

 

[motomech]

Wiring:

Battery:

My plan is to wire the two batteries into a the A side of a 4-flat boat trailer wiring extension cable.

This plug is polarized with an A side and a B side, is good for plenty of amps, and will handle a lot of connect/disconnect cycles. With dielectric grease, they hold up the elements reasonably well, and this one will live in a pannier. Even better, there is at least one on the shelf in my garage right now.

I'll make a patch cable to wire the charging leads on the charger to a B side plug in parallel configuration.

I'll use a parallel balance lead, semi-permanently attached to the charger.

For charging, I'll have 3 connections to make (two interchangeable balance leads, these are polarized, right?) and a 4-flat. For discharging, I'll have only one, impossible to mess up connection to make, and maybe a switch to turn on.

Controller

I'll wire the controller power leads from the battery such that it puts the two batteries in series on the B side of the connection, with an additional connection for the on/off lead (will it hurt the controller to leave this lead hot all the time, or just damage the battery connections over time?) I'm also thinking of switching the 4-flat to 5 flat, and shortening the barrel on the 5th terminal so it makes electrical contact after the other 4, then using it as the power up lead on the controller.

I'm assuming that the motor connection between the patch cable that comes with the motor and the controller is plug and play, and the same with the 3-speed switch and throttle.

Did I go horribly awry anywhere there?

Given that I'm going to be riding in sand/salt/snow/rain, should I pull the motor apart and spray it down with corrosion-x or boeshield T-9 or something like that?

My plan is to wire the two batteries into a the A side of a 4-flat boat trailer wiring extension cable.

The problem with trailer connectors, as explained by someone here, is the poor crimp connection inside the plastic molding.
Having said that, I am running one on a MXUS mini @ 12S & 22A w/ no problems, so I think it would be fine for your app.