Phat Bike Build

[jkbrigman]

Here's the before photo right after getting the bike home from the LBS. It's a slight knockoff of the Electra Townie, but with less of a crank-forward emphasis and a slightly smaller (but still big) central triangle. The tires on this bike are HUGE: 2" thick, 26" diameter. The thickness of the tires and design of the frame make it look smaller, like a big kid's tricycle. But this bike is very large: when I sit on it, my belt comes to the top of the door on most cars. It's good to be king!

 

[jkbrigman]

The Phat Bike Rides! This was at the beginning of a 28 mile test ride.

This test used the old battery harness. Made from 12GA stranded copper with 4mm bullet connectors and one anderson powerpole, this harness needs replacing with a heavier one with better, tighter connectors. In the past, this harness has come apart and stopped the bike. Fortunately, no shorts or fires, but I'm living on borrowed time anyway.



Here's a component list of what I added to the stock frame:

9c 2810 rear DD hub motor
25A Infineon controller modded to 40A
Cycle Analyst v2.23
18S2P in the bag (on this ride)
Falcon EV bag
Self-built battery harness
Thumb throttle, no regen
SKS fenders
TransIt Rear Aluminum Rack
TransIt Rear Pannier

 

[jkbrigman]

Sunshine and temps in the high 60's made a Phat Bike test run mandatory, so I took advantage of the weather to test the bike on the route and see if it's usable as a commuter. Results are good, but not good enough. Read on, your comment welcome:

First, The Bad News:

A 12mph headwind from the south had a very power-draining effect on the 15Ah 18S3P LiPo: the headwind cost almost 3Ah over 4 miles as the motor was pulling 30 Wh/mi there for a short distance. It drained the cells heavily early into the test run.





The Good News:

The ride is balanced, stable and features plenty of shock absorption even for a hardtail from the fat tires and suspension seatpost . The triangle battery bag and LiPo works great low and in the center. The throttle is working "ok" but the non-anatomic handlebar grip is annoying: it offers no distribution of force over the left palm, so that hand keeps wanting to go to sleep from the nerve pressure.

The drivetrain is useless at speed: I was unable to pedal fast enough to contribute any useful energy at cruise speed and this shows up severely in the energy consumption. This bike eats energy at twice the rate of the recumbent for less speed. None of the intermediate gears on the bike were useful while applying electric power: the only time I used them was if I pedaled the bike with no electric power at all.

I realized an interesting effect of pedaling at speed: not only do you cut energy needed from the battery in the first place by pedaling, but you can help keep the motor up in it's most efficient speed range. With the extremely low gearing of this bicycle, I was unable to help the motor stay at speed, so I saw more heat buildup on the motor than ever before. Without good "legs", I couldn't keep this motor turning fast enough to stay efficient.

My thesis means that if you see 200 watts savings from pedaling, maybe you contribute 100 watts and save another 100 watts keeping the motor's back-EMF working.

Summary of the data:
Distance: 26.04 miles
Consumption Rate: 26 Wh/mile
Total Energy: 678.55 Watt-Hours
Total Current: 9.887 Amp-Hours
Max Speed: 27.9 mph
Avg. Speed: 17.8 mph
Total Time: 1hr 27min

This is just too slow. I need another 5mph!







Conclusions:

• I need more speed! Modify the pedal drivetrain to be useful at speed so I can help keep the motor in it's happiest speed range.
  
  This bike needs a fairing and maybe even a tailcone. I wonder if replacing the pannier with a rear trunk on top of the rack would help aero the same way a tailcone would.
  
  The new battery harness worked flawlessly: I'll stick with 10GA and good insulated pairs of 4mm bullets from now on.
  
  Get rid of the front derailleur and get the anatomic grip back.
  
  Regen would help - I lost energy at 3 stoplights that could have been reclaimed.
  
  Get a helmet with a face shield. There were bugs out even in December!

I solicit your comments and suggestions for making the bike faster and more efficient!

 

[jkbrigman]

Checked out these fairings:

http://www.zzipper.com/Products/prod_upright.php

Users report a consistent 2mph speed increase and improved comfort in cold weather. They are expensive. The one I like is $350. I understand some people take a piece of lexan and the equivalent of a "male mold" and an oven, and manage to melt the lexan into a fairing shape. I wonder if this is something I could do at a TechShop?

 

[jkbrigman]

New 11-32T rear freewheel ordered from ebikes.ca. A thorough check of LBS's (called three) demonstrated that this part is not available locally, at least as a new part.

JKB

 

[pendragon8000]

Do you have a v3 CA? If so , limit the current to the current used at Max speed, use a moderate throttle ramp up. If not I would suggest getting one as it effectively increases your range by an economical amount. Also Max out tyre pressure?

 

[jkbrigman]

Do you have a v3 CA? If so , limit the current to the current used at Max speed, use a moderate throttle ramp up. If not I would suggest getting one as it effectively increases your range by an economical amount. Also Max out tyre pressure?

Thanks! I have a v2.23 CA and it will do that. Good point on the tire pressure: I'm running max (60 psi) right now, but I'm thinking I'll need to go back to Schwalbe so I can run higher pressures. By the way: nice build with the Scott Spark!

 

[jkbrigman]

Quick test today in zero headwind conditions revealed some important information:

1) Power consumption on this bike is highly sensitive to the rider's position. I could affect power consumption very directly by how much I sat up or bent over the handlebars, causing it to vary by as much as 400 watts and at least 100 watts no matter what the conditions.

2) When you fall below the motor's efficient rotational speed, the effect of wind resistance has a near-doubling effect on power losses over it's affect at or above the motor's "sweet spot". I realized how crucial it is to keep a 2810 in a 26" wheel spinning at 20mph or more.

At least the results are consistent: 25 Wh/mile, 6.8 miles, 170 Watt-hrs total. With 600-800 watt-hours to burn to 80% discharge, that gives me a theoretical range of about 32 miles.

Holy crap. I need a fairing.

 

[pendragon8000]

Thanks! I have a v2.23 CA and it will do that. Good point on the tire pressure: I'm running max (60 psi) right now, but I'm thinking I'll need to go back to Schwalbe so I can run higher pressures. By the way: nice build with the Scott Spark!

Yeah the spark is pretty sweet.

I get similar kw/hr to you but at 37.5mph (60kph)... I have power limited to 1.2KW with a mild throttle ramp up and peddle moderately hard on take off.

 

[jkbrigman]

I get similar kw/hr to you but at 37.5mph (60kph)... I have power limited to 1.2KW with a mild throttle ramp up and peddle moderately hard on take off.

That's actually pretty phenomenal for a DS mtn bike. And I start out the same way you do - pedaling - I never "goose it hard" from a standing start. Are you contributing ANY pedal power at that speed? A stock mtn bike crankset isn't going to reach 37mph.

There are a number of factors I'm looking at changing to try to effect improvement:
- pedal system (I have an 11-28T 7-speed freewheel coming)
- wiring and connectors: the way this bike draws current, I know I need to swap out some of the small-gauge wiring and connectors for larger
- fairing: I've simply got to have a fairing. I'm like a billboard moving forward on this bike. Not to mention I could use the windbreak if I'm going to ride here anytime soon in the cold weather.
- It's possible I could have a bad cell. I've not done any study of the condition of the packs yet. That's to be done.

JKB

 

[pendragon8000]

I do contribute a few kph to the speed but my gearing makes it hard to pedal hard because my legs are ripping around so fast. I have 44 front 11 back with 29 inch wheels. I'm going to put on a 48 t up front I just have to get around to putting it on. At that speed though it makes almost as much difference in speed just to duck down into aerodynamic position. Maby the 48 tooth ring will let me push a bit more.

 

[jkbrigman]

The Phat Bike came stock with a 14-34T "MEGARANGE" rear freewheel. When I installed the 9c 2810, I simply transferred that freewheel over:



One of the to-do items is to swap out that stock freewheel for a new 11-28T freewheel from ebikes.ca. Ordered and received the new 11-28T freewheel and went a little crazy and ordered a new crankset too.

New fire-breathing headlight received. It's the one that's on ebay and can run up to 90 volts, previously mentioned in the forums. The mounting bracket is crap and the wiring needs to be reinforced, strain-relieved and protected. It would majorly suck to short out 18S LiPo in the headlight circuit...might just install an inline fuse for that headlight....

 

[pendragon8000]

Have you tried a plug pack? I STILL haven't . But it should work.

 

[jkbrigman]

Have you tried a plug pack? I STILL haven't . But it should work.

Not yet. What about a small switching power supply for doing the conversion?

 

[teklektik]

I dream of a nice, low-cost DC-DC converter for 75-to-12 volts that I could install in the pack and leave there, powering a bike "low voltage bus" for headlight, taillight, turn signals and horn.

Have you tried a plug pack? I STILL haven't . But it should work.

Not yet. What about a small switching power supply for doing the conversion?

That's what's in the laptop supplies plus they're waterproof and good to 240v. The Toshiba ADP-60RH is well tested for this ebike application and puts out 15v @ 4A - nice for automotive accessories. You can search around for netbook supplies if you want an even smaller unit. I recently picked up a nice small ASUS netbook supply (12v @ 3a) which works very nicely although 12v is a tad low for automotive lighting (but still okay).

Unless you have a wimpy horn, you may be better off just running a 12v battery tap for your horn. They have a large current draw and huge electrical noise (basically a big interrupting inductor). It's hardy worth over-specing the converter for an occasional irritated blast... there are no material consequences from a cell balance perspective.

 

[jkbrigman]

The Toshiba ADP-60RH is well tested for this ebike application and puts out 15v @ 4A - nice for automotive accessories. You can search around for netbook supplies if you want an even smaller unit. I recently picked up a nice small ASUS netbook supply (12v @ 3a) which works very nicely although 12v is a tad low for automotive lighting (but still okay).

Unless you have a wimpy horn, you may be better off just running a 12v battery tap for your horn. They have a large current draw and huge electrical noise (basically a big interrupting inductor). It's hardy worth over-specing the converter for an occasional irritated blast... there are no material consequences from a cell balance perspective.

No horn installed yet - I'm giving some thought to that, maybe even go for an air horn.

My search-fu seems to be weak these days....teklektik, you saved the day: I have TWO of those supplies just lying around. Time to break out the wire cutters and spare anderson connectors....DC bus, here I come!

so now I've got FOUR Phat Bike mods in the queue to report back on:
- Change out freewheel (ebikes.ca)
- Change out crankset (vueltausa.com)
- Laptop P/S dc-dc converter (my trash can)
- New headlight (ebay)

 

[jkbrigman]

Results: up from 14mph to 18mph sustained pedaling. If I'm willing to spin "too fast", I can reach 22mph. (21.7mph according to the CA speedometer function)

I went through all the gears to compare new freewheel to old and it's OK. The 28T "first gear" works great, you can't tell much difference between it and the 34T MEGARANGE gear. I can start from a standing stop on the large front chainring just fine with the 28T rear 1st gear.

There's more friction in the new freewheel. I don't fully understand this. I'm hoping this will lessen with use.

So going from 14 tooth to 11 tooth "high gear" bought me about 3 or 4 mph. This isn't fast enough. I have to swap out the crankset to get the larger chainring on the front to get more speed.

 

[jkbrigman]

Changed my signature to reflect the new 19 Wh/mi for the Phat bike. Fixed problems with the derailleur and changed out the freewheel. This one change gave remarkable results, getting me below my initial target of 20Wh/mi. Now that I can add useful energy at or above 20mph, consumption has gone from 26 Wh/mi to 19 Wh/mi.



This was over a 24 mile trip "out and back" over the same route. On the outbound leg, I was surprised to see 13Wh/mile, but at a slower average speed of about 16mph. On the return leg I spent more power and averaged 20mph.

The work is far from done to get closer to 30mph average. Next steps are to swap out the crankset so I can have a 52T front sprocket (requiring a very LARGE allen wrench) and improve aerodynamic efficiency by adding a fairing. After the fairing, add a rear rack "trunk" and remove the pannier, which is hanging out in the wind.

The theory of "100 watts at the pedals saving more than 100 watts at the motor" is being validated by testing. On today's test run I was able to save as much as 400 watts of power consumption in the motor by adding my puny 100 watts when running 18-22 mph.

Conclusion: With a hub motor, plan to change out at least the rear freewheel if you want your ebike to reach speeds of 20-22mph while being able to add power via the pedal drivetrain. Plan to change out the front chainring (or crankset if needed) if you want to add power past 22 mph.

My last conversion, a recumbent, had a 52T chainring up front that was good for adding power up to 33-35mph. Let's see if I can reach that on this conversion by swapping out the crankset. Will do so and post results....

 

[jkbrigman]

The new crankset and freewheel testing is successful!

With the former pedal system, you couldn't contribute any energy past 14mph. That prevented the bike from reaching the motor's "sweet spot". (remember, this is a 9c 2810, so the motor builds up decent back-EMF at about 20-22mph on 72v and 26" wheel). With the stock crankset, consumption was terrible: 26Wh/mi and speed was awful: 14mph average. The bike could briefly reach 26mph peak. The rest of the time, 14-18mph. (swapping out the freewheel bought more speed, about 4mph more, but wasn't yet reaching the motor sweet spot)


In other words, with the stock crankset and freewheel, the Phat Bike is a failure!. You can do those speeds on a road bike without a motor.
However, I swapped the stock crankset out with this one (http://www.vueltausa.com - thanks to neptronix!):


Doing this made an immense difference! The new crankset allows me to contribute energy all the way up to 31mph peak. 25mph sustained on flat and level ground is possible by using both the motor and pedaling. Consumption is now 19Wh/mi because you can now spin the 9c 2810 motor (26" wheel) up to 20mph at about 450watts. This means the battery can now cover the 33 mile commute distance, where prior testing put that into doubt.

The 25mph sustained is on flat, level ground. Climbing hills, I lose speed to keep consumption at 500-800 watts. Overall average is 18mph. Still too slow, but a huge improvement over 14mph average.

Verdict: changing out the freewheel and cranks = success. Total cost less than $80.
Next: It's time to do an actual commute on the Phat Bike.
What's so special about that? It's 66 miles round-trip!

 

[jkbrigman]

On the testing for the freewheel swap-out, turns out I got my first flat on the motor wheel:


When searching for the object that penetrated my nice, kevlar-belted "Hemisphere" tire, here's what I found:
View attachment 1

Looking at it in my gloved hand, it looked like a tiny steel needle:


My working theory is that this is a "thread fragment" from a steel belted tire. I hear from others on E-S that they've had a flat from the same kind of item.
I can't possibly believe this could be a needle, so I'll go with the "steel belt fragment theory".

Anyway: kevlar belt didn't stop it. Nor did innertube. I'll probably keep running this tire/tube combo, but will keep an eye open in case I need to switch.
Now I understand why everyone makes a big fuss out of getting a flat on the motor wheel tire: it's difficult to fix a flat on a motor wheel. I've fixed flats before on the road, but this one, I'm not so sure I could have gotten it fixed...

 

[Ykick]

Rear tire? The front usually rolls over and kicks up things like that and they're at a perfect angle to spear the rear tire. Never ceases to amaze me how many rear flats are actually caused by the front tire. I guess those unicycles do have a clear advantage in that regard, LOL....

Did you need to change the bottom bracket for the road crank? I'm about ready to go with a 53T and LBS said something about perhaps needing a different BB?

Looking good.

 

[jkbrigman]

Rear tire? The front usually rolls over and kicks up things like that and they're at a perfect angle to spear the rear tire. Never ceases to amaze me how many rear flats are actually caused by the front tire. I guess those unicycles do have a clear advantage in that regard, LOL....

Did you need to change the bottom bracket for the road crank? I'm about ready to go with a 53T and LBS said something about perhaps needing a different BB?

Looking good.

Thanks Ykick for the props, means a lot coming from an experienced ebiker!

No need to change the bottom bracket at all: I had a square taper bottom bracket and both the old and new cranksets fit that. If I had one of the other types of bottom brackets, I'd have had to change it out. I borrowed the tool to do that too, so it would have been a matter of just buying the hardware and installing it.

There were two challenges with the crankset swap:

1) I HAD to have a crankset removal tool, I couldn't get around that. Once I got the tool (I borrowed one) it was a snap.
2) The front derailleur was very tricky to move. I tried to take a shortcut and just loosen the derailleur and move it up the seat tube. I scratched the crap out of the seat tube and didn't have to do that, I should have just removed the cable from the derailleur, moved it, then tightened it down and reinserted the cable. That would have worked much better.

I can't tell you one way or another what might have caused that tiny wire to pierce the tire, but I can see what you are talking about: maybe hitting a rock with the front tire that jostled the wire on the ground and positioned it to go into the rear tire. The shocker about it was how the sharp, hard wire went DIRECTLY into the tire: there was no angle to it at all: it pierced at exactly 90 degrees and it was so long that it went clear into the tube with at least 1/4" still in the tube when I removed it.

SLIME, or some equivalent, would have helped in this case and sealed the puncture. I would definitely want some kind of tube sealant had I been on a long tour ride instead of a short ride ("only 24 miles" ) But...this kind of projectile would have come loose inside the tube and "floated" around in the SLIME. I seems reasonable that it would have actually re-penetrated the tire from inside at a later time. You would hope the SLIME would stop that hole too.

 

[jkbrigman]

A few postings ago, I planned FOUR MODS to the bike. Time to report on each item:

- Change out freewheel
- Change out crankset
- Laptop P/S dc-dc converter
- New headlight

Change out freewheel
Problem: Can't pedal enough to add any energy and keep the motor at a low-current-consumption speed.
How: tried to buy 11-28t freewheel at LBS. They said those don't exist. I politely thanked them and hung up, ordered it from ebikes.ca. Installed it with the nice custom freewheel tool.
Website: http://www.ebikes.ca.
Result: Problem solved about 50%: The bike went 4mph faster, uses less energy (from 26Wh/mi down to 19Wh/mi!), shifts great.
Rating: 5 stars! Cost: about $40 for the freewheel and $12 for the tool. Shipping about $20.

Change out crankset
Problem: Can't pedal enough to add any energy and keep the motor at a low-current-consumption speed.
How: Got recommendation of vueltausa.com for a replacement crankset. Looked 'em up on the web, found an awesome 52t front crankset for...$30, $9 shipping. Bought it. Borrowed crank puller tool, installed new crankset.
Website: http://www.vueltausa.com
Result: Problem solved the "other 50%": Bike went ANOTHER 4mph faster, now can provide pedal input all the way up to 35mph and still uses less energy. Got front derailleur to work OK with it. Brakes are beginning to show their limitations.
Rating: 5 stars! Cost: $30 for the crankset and $9 shipping.

Comment: Swapping out both the freewheel and the crankset really makes the 9c 2810 motor wheel shine! I can now cruise easily at 22mph on 200-400watts and can push the bike to 25mph on flat/level ground. 31mph is possible for limited times depending on terrain. I was ready to get rid of my big 2" tires, but the new pedal system eliminates that concern and allows me to keep running a big, soft safe tire that can handle the broken glass and debris on the side of the road. If you are commuting long distances, this is the MUST MOD for your ebike!

Laptop P/S dc-dc converter
Problem: Would like to have low voltage DC from the big 18s pack.
How: Use a laptop or wall-wart power supply to drop pack voltage to low voltage DC.
Result: Haven't gotten to this yet.

New headlight
How: ordered the "up to 90v capable 800 lumen" LED headlight off ebay. Installed new headlight, runs off my 72v (18s) pack. NOTE: this light did not come with a mounting kit or on-off switch, so I had to make some parts to "finish" the light. It's pretty crude: the back-end of the light is just an open cylinder with two screw-slots
Website: http://www.ebay.com. Here's the same light that INCLUDES a bracket foronly $20 with free economy shipping: http://www.ebay.com/itm/Motorcycle-...uper-White-Eectric-of-12W-1290V-/261118647712
Result: Crude, simple, fast install. Brilliant bright light, doesn't drag down the pack at all. No added battery to charge. I'm amazed at how well it works, wish I'd gotten one sooner.
Rating: 3 stars. Cost: about $36 off ebay

I wouldn't operate an ebike without a high-power high-output light like this. Whether you get the magicshine clone that has it's own battery or you get something like this that runs off the pack, a bike light doesn't give you enough forward lighting to avoid obstacles. I could clearly see the motorists behave better around me with this light: I watched them see me, recognize me and drive safer!

 

[pendragon8000]

nice work. yeah the 11 tooth gears with 7 or 8 speed are non existant in the normal bike world. glad you got 35mph thats great, how mch power consumption?

 

[jkbrigman]

nice work. yeah the 11 tooth gears with 7 or 8 speed are non existant in the normal bike world. glad you got 35mph thats great, how mch power consumption?

Thanks man! I appreciate the good word from an alumni of a studly bike build!

Consumption is now 19Wh/mi, about 450watts up to 25mph(40kph). The 25mph/40kph sustained is on flat, level ground. Climbing hills, that number goes to crap as I lose speed to keep consumption at 500-800 watts. Overall average is 18mph/28kph as shown by the CA. Still too slow, but a huge improvement over 14mph/23kph average.

I need to dial back the verbage on my posts and feature the data more prominently. I had this information in my prior post, but even I didn't want to go find it myself. So I'll go back and edit, dial back the flowery prose a bit.