Diamondback Apex trail build (was Cannondale Rush Carbon)

[scfoster]

New to this forum and looking for advice on an ebike conversion or purchase.

I have a 2008 Cannondale Rush 3 Carbon frame bike laying around (yes I should have sold it for the case a long time ago) the specs for the bike are here.

Cannondale Rush 3
Model Code: 8Vm3
Frame: rush CarBon, 110 mm
Fork: LeFty speed Bonded dLr2, 110 mm
Rear Shock: FoX FLoat rp23
Rims: maViC Xm819 ust disC, 24 hoLe
Hubs: CannondaLe LeFty Front, sun ringLe dirty FLea rear
Spokes: dt swiss Competition
Tires: maXXis CrossmarK XC ust, 26 X 2.1”
Pedals: CranKBrothers egg Beater
Crank: Fsa aFterBurner megaeXo, 22/32/44
Chain: shimano 9-speed
Rear Cogs: sram pg-970, 11-34 Bottom Bracket: Fsa megaeXo Front Derailleur: shimano LX Rear
Derailleur: sram X-9
Shifters: sram X-7 trigger
Handlebar: Fsa XC-281aos, 25 mm rise
Stem: CannondaLe XC3 si, 31.8 mm
Headset: CannondaLe headshoK si
Brakes: aVid juiCy 7, 160/160 mm
Brake Levers: aVid juiCy 7
Saddle: Fi’Zi:K nisene sport mg
Seatpost: CannondaLe C3 2014 aLLoy
Sizes: s, m, L, X
Colors (codes): Vredestein team (gLoss) (rep).
uni CarBon w/patriot BLue gLoss) (BLu).
Extras: CannondaLe V-teCh grip


I'm 6' 3" tall (190.5 cm), 195 lbs (88.5 kg) with a daily commute of 5.1 miles each way (8.2 km) with a vertical climb/descent of only 300ft (91m) with only one relatively steep section. The road is 50-50 urban street (with break down lane) and city (lot's of stoplights, parked cars and sidewalks). I want to assume I will NOT have the ability to recharge the batteries when at the office, so a range of 10 miles (say 20km) will be necessary. I would prefer to keep up with traffic in the City and would love to be able to do 40 mph if necessary.
I currently use a BMW 800GS motorcycle and it takes around 20-30 minutes to get to work. Found a place to park for free (thank you Amtrak) so gas and parking aren't much of a consideration as the bike get 50mpg. Looking more for the convenience of parking right outside the office door (bike stand right outside) and the occasional LIGHT mountain biking trail use. Not deluding myself that I'll use this for commuting 95% of the time, if I use this bike.
Regarding technical skills, I know how to use a soldering iron, voltmeter, I'm an aeronautical engineer and I do all my own maintenance on the motorcycle. So assembling things shouldn't be an issue. Willing to try and break a few things along the way (stuff happens). If I destroy the bike, I'm okay with that. Already thinking about how to fashion a torque arm to work with the carbon/aluminum frame.

So I'm looking for advice on what would be the best path forward or whether this bike is even suitable for conversion? Or, should I head over to Walmart to buy a steel framed mountain bike as the base?

I know this isn't going to be cheap but I'm willing to cut costs by assembling things myself and doing some testing.

Thoughts?

Thanks in advance (Scott in Delaware, USA)

 

[MadRhino]

I wouldn't build with a hub motor on this frame, unless I can make a complete new swing arm with alu or steel. This is a good bike to fit a GNG mid drive though.

 

[John in CR]

If I had a carbon frame like that "laying around", then I'd use it for sure, since to me "laying around" means it's absolutely fair game for hacking. The bike is old enough that any weaknesses should be easy to find online, and easy to address with carbon fiber and epoxy to strengthen, reinforce, and add what's needed like a battery box, torque arms, etc.

 

[speedmd]

I have both a modded GNG 1 and the BBS02 750 watt kits. If your just commuting and want it stealthy the bbs is the way to go. Lots of factory made (8 - 11AH) batteries should fit the frame opening also and easily make the round trip. Will make a great ride.

 

[scfoster]

If I had a carbon frame like that "laying around", then I'd use it for sure, since to me "laying around" means it's absolutely fair game for hacking. The bike is old enough that any weaknesses should be easy to find online, and easy to address with carbon fiber and epoxy to strengthen, reinforce, and add what's needed like a battery box, torque arms, etc.

I was thinking the same thing. Carbon fiber in this application is a LOT stronger than it looks.
If I wreck it I can always get a new swingarm.

Wondering what if I can get a 48V hub on it. I think the spacing is 135mm. Any good kits?

Thanks for the comments so far.

 

[mlt34]

I'd be really worried about blowing out the dropouts on that thing with a 48V kit.

I agree with the comment above that you want a BBS02, assuming it's compatible with that bottom bracket. The installation process is pretty easy (you don't need to be a rocket scientist, or, well an aeronautical engineer to do it). You could run the 48V you want and get a good 1000 watts. It'd be an insanely fun ebike that way. But a hubmotor build, I don't think that's the way to go. You'd be limited to a smaller, weaker hubmotor to try and not destroy the bike.

BBS02 sources: http://em3ev.com/store/index.php?route=product/product&path=36&product_id=166
and: http://www.bmsbattery.com/central-motor/646-48v350w-bbs01-bafang-central-motor.html

Ooooh I'm drooling over seeing that bike electrified...

 

[John in CR]

You're an engineer, so anything can be made to fit anything. For the most part until you get into power too high to consider putting on a carbon bike frame hub motors come in 2 varieties, direct drive and geared. Direct drive means the motor shell is the rotor of the motor. They're heavier due to the low operating rpm but same torque requirements, but greater outside surface area for greater heat dissipation. They handle higher current and voltage better than geared, and can be easily modified to give a light bike performance that makes operating in the open space available in traffic much safer by making cars the low speed objects you avoid as opposed to you being the low speed object hundreds of vehicles must avoid squashing on every trip. Geared hubmotors have a motor inside operating at 4-5X wheel rpm with a plastic gear planetary reduction. Geared are more efficient during acceleration, but are more limited in terms of pushing them well past design limits, because they try to optimize the motor and gear reduction (with plastic gears) to suit the job.

If you went geared, you'd probably need to go with 2wd, which would be fun and zippy, but going from a motorcycle as a commuter I think you'll be left wanting more and that means a redo of the whole system. You can go directly to a higher level of performance with one of the larger direct drive motors, and then if you want to embarrass cars and catch motos by surprise all you have to do is mods for better cooling and crank up the current and voltage. At 275lb I'm a beached whale in comparison to you and my Cannodale SuperV based ebike is capable of over 100mph and I have no concerns about pointing it up any paved hill regardless of grade or length.

Hints:
Look out for name brands that cost far more but use essentially generic parts. I have little doubt you'll want to increase performance, so bite the bullet in the beginning and get more controller than you need initially. Then it will be capable of the higher current and voltage you'll eventually want. When you're ready to mod a motor for better cooling, don't copy the crowd, because what is typically done isn't very effective. Contact me, I think we can help each other by using your tools and knowledge to maximize the effectiveness of my latest centrifugal fan approach using external blades to cool a hub motor.

John

PS- Have you looked at Audi's ebike? Since you're starting with a carbon frame you might consider going a similar route with the motor out of the wheel for an urban and trail assault bike. It just wouldn't be a street beast capable of creating the safe spacing that I do by using speed and acceleration, but it might make up for it by easily handling shortcuts through parks and up and down staircases.

 

[mlt34]

If you went geared, you'd probably need to go with 2wd, which would be fun and zippy...

…and pretty tough to do with that lefty fork.

Speaking of which, I don't know why its still called a "fork". It's more of a chopstick now, isn't it?

 

[Drunkskunk]

That carbon rear swingarm wasn't built to withstand torque being put on it in the directions that a hub motor will. If you go for anything above pure pedal assist levels of power, you're going to need a new swingarm or a dramatic rework of the original. Also remember that a hub motor is a heavy beast, increasing your unsprung weight, and affecting your pivot points and suspension mount points. Carbon parts don't like to be abused or pushed outside of spec.

Best alternative would be a bottom bracket drive like the BBS02.

 

[John in CR]

You guys don't have much faith in SCFoster as an aeronautical engineer. One of the things I like about starting with a carbon frame is that strength can easily be added wherever it's needed and by spreading the stresses properly and adding strength in the right directions very little added weight can go a long way. We've got people hacking and welding on aluminum frames that makes them markedly weaker, especially in the HAZ, and all those people get are pats on the back and praise about the mods they do.

As long as SC can be satisfied with his own finish work, I have faith that he can analyze the stresses on the structure and make any necessary changes. This can all be direct mods that don't detract from the existing structure other than to sand off decorative paint to ensure a good bond with the new material. That's what attracts me most about starting with a carbon platform. No, I wouldn't take a carbon bike, glue on some thick steel clamping torque arms, and go for motorcycle performance. I would however be excited to hack into a "laying around" carbon frame, cut the dropout size to fit a big hubbie with a properly sized axle, imbed clamping long tapered steel torque arms using a carbon fiber tape wrap to secure them and spread that load, strengthen all of the swingarm with a wrap or 2 of carbon, use unidirectional carbon wrapped in multiple directions to greatly increase the strength of all high stress points, and mold a 2 piece battery box with a glass on the inside (for electrical insulation) and carbon fiber on the outside that fits perfectly to the main frame for a saddlebag type front triangle battery box. I'm no trained engineer and I know with certainty that I could build a sufficiently strong and lightweight extreme power ebike with that approach.

Actually, for extreme street running a longer wheelbase is necessary, so I'd extend the existing swingarm by 4" or more, and use carbon fiber to imbed new clamping steel dropouts. Another option would be to get it up and going first, and then fabricate a new swingarm that not only lengthens the wheelbase, but also lowers the saddle and adds a bit of trail to the steering geometry for better high speed stability. The controllers I have to use take up a lot of real estate, so as part of the swingarm extension I'd include enough space near the pivot to hide my controllers while still providing them with sufficient ventilation.

Since I'm too cheap to buy a carbon bike, now I'm on the search for one that someone broke. My SuperV's main tube was collapsing at a crack near the shock attachment rendering the frame worthless, but I fixed that permanently by stuffing it with fiberglass cloth, injecting it with epoxy, and bolting a steel plate with shock attachment tabs directly to the now solid main tube. I'm sure I can repair any damaged carbon bike even if it requires such extreme strengthening as going solid core in the repaired area.

John

 

[scfoster]

I agree about the "chopstick" reference.

Not so concerned about the weight/torque of the hub motor causing damage, especially if a torque arm is added. Since carbon fiber is so unforgiving (doesn't bend/yield to give a warning of impending failure) a pretty large factor of safety is "built-in" when components are being designed. This would be especially true for a mountain bike, where the impact load (think aircraft arresting hook on a carrier) is probably pretty large when landing after a jump. I recognize that said factor of safety would be largely eaten up with a hub, so banging around in the woods would probably be a bad idea. Of course potholes in the City can be pretty unforgiving

I do like the BBS02 but wonder what the top speed would be with it. The price for the complete kitwith battery (22Ah) looks to be about $1300 plus shipping. Not bad.

I did find a "Black Lightning" complete kit from Hi-Power Cycles, but wonder if the $4000 price and extra weight is worth it. Also not sure if the wheel will fit my 135mm wide drop in.

 

[John in CR]

I did find a "Black Lightning" complete kit from Hi-Power Cycles, but wonder if the $4000 price and extra weight is worth it. Also not sure if the wheel will fit my 135mm wide drop in.

That price is way out past what I was warning about earlier. My 100mph bike didn't cost nearly that, with bigger more capable battery, dual higher power each controllers, etc., and the $900 I paid for the pedal bike.

 

[scfoster]

Pulled the trigger on the 48V 750W BBS02 kit from EM3EV.com, including a 50V 22Ah battery. Total price, including shipping paypal fees and currency conversion was $1560

Thanks for all the suggestions..... Now the wait begins.

 

[speedmd]

Hi scfoster

You will like the feel of bbs on the light weight bike. The 22ah pack is much bigger than needed unless you plan some significantly greater distances than you noted. I built one up in a aluminum santa cruise bike like yours and can fit 16ah of 48v lipo in the frame center and I ended up running mainly a half pack (8ah) most all of the time and can easily go more than the distances you were looking for and still have plenty of charge remaining with the half pack.

They carry these smaller packs pictured below that may fit your frame. Several other good dealers have similar ones that are even a bit smaller. It feels much nicer with the weight in the frames center.

You also will want to make sure your BB shell is not too thick. Not a deal breaker if you don't mind grinding away a bit of material if it is too tight a fit.

 

[scfoster]

Hi scfoster, You also will want to make sure your BB shell is not too thick. Not a deal breaker if you don't mind grinding away a bit of material if it is too tight a fit.

The fit is a concern but I'll cross that bridge when it arrives. Worst case, I'll get another frame.

The initial plan is to get a seatpost mounted carrier and a bag to house the battery.

I agree about the battery more than likely being way too big, but I figured I can always downsize to something smaller, while having the larger battery if I want to take longer rides.

The full suspension frame doesn't leave a whole lot of room for a battery, so I'll have to experiment.

 

[speedmd]

Your planing on having a 20 pound battery hanging off a flimsy single arm rear rack. Don't hit any bumps. I would worry a bit if bumpy. I would ask paul if he has or can make you one that will fit the frame opening. 11AH should be good for at least 15 miles with this kit going by what I am getting. Your milage may vary. LOL

 

[mlt34]

Yea I worry you'll be asking a little too much if that seat post mounted rack. Thats a big battery. Awesome battery, but heavy nonetheless. Worst case there will be many people on this forum that would want to buy it off you if you needed to downgrade :wink:

 

[scfoster]

Two things.... first I would fashion a brace from that triangulates from the bottom of the rack to the frame below. But I appreciate pointing out the need for it.

Second, what is a good source for batteries in the USA? Shipping on a single battery from Hong Kong would be high.

 

[mlt34]

Triangulating it to the seat tube would be a good way to go.

What batteries are you looking for? RC lipo from hobby king shouldn't be too bad to ship.

In the US you can get AllCell batteries but they are just chinese cells in an overhyped wax mold. Kinda pricy. You can get them from Ebikes.ca

There's also HeadwayHeadquarters on the west coast, but again, Chinese cells. Good quality, but everything is chinese. That's why we pretty much buy the batteries straight from China. Cut out the middle man.

 

[scfoster]

Got it. Is there any value in just building my own? That way I could create a custom bag in the necessary shape for the frame. Don't have a sewing machine but I do know how to make patterns and have someone else do the sewing.

One thought is if the battery pack were removable, I could take it in to work and recharge it there. That would mean the pack would only have to give me 6 miles (say ~10km). Not very far at all.

Battery technology is something I know next to nothing about. I'm assuming there's a world of difference between a dewalt/milwaukee tool li-ion battery and something that needs to provide continuous power for around 30-40 minutes. Correct?

Otherwise, I'd rig up a connector for one of the larger Li-ion tool batteries (or multiple), then just use a charger for that brand at the office.

 

[mlt34]

Got it. Is there any value in just building my own? That way I could create a custom bag in the necessary shape for the frame. Don't have a sewing machine but I do know how to make patterns and have someone else do the sewing.

One thought is if the battery pack were removable, I could take it in to work and recharge it there. That would mean the pack would only have to give me 6 miles (say ~10km). Not very far at all.

Battery technology is something I know next to nothing about. I'm assuming there's a world of difference between a dewalt/milwaukee tool li-ion battery and something that needs to provide continuous power for around 30-40 minutes. Correct?

Otherwise, I'd rig up a connector for one of the larger Li-ion tool batteries (or multiple), then just use a charger for that brand at the office.

Building your own is something that is definitely doable and the big advantages are 1) you know the work done is quality work, 2) you understand what's going on in there in case you ever need to do a repair, and 3) you can design it in any shape you want to fit your bike. It's also not that hard - remember most of these packs are built by young women in Asian sweatshops.

However, building your own isn't a necessity, and there are lots of good off-the-shelf batteries that could fit your need. A removable battery is definitely nice. The main downside is they are easier to steal, but you're not going to be leaving that bike alone any time soon, I'd imagine. Plus, if you're removing the battery for charging then the bike is less of a target for theft. If anything, someone's going to want your fork before they take your motor.

For removable batteries, this style could go on a rear rack like you're talking about:

You just bolt that plate onto your rack (may have to make some kind of spacer/adapter if your rack isn't flat) and then your battery slides onto the plate and locks. Then you slide it out and take it with you when you want to charge.

I usually get batteries like those from BMSbattery, such as this one: http://www.bmsbattery.com/48v/403-48v-10ah-lithium-ion-alloy-shell-ebike-battery-pack.html
or this high c-rate one might be better for you: http://www.bmsbattery.com/48v/609-48v-15ah-lithium-ion-alloy-shell-ebike-battery-pack.html

Those two would give you your 6 miles easily. They'd probably give you more like 25 miles depending on use. That's a good thing though, because as soon as you hop on the bike you're going to want to use it for a lot more than just your normal commute :lol:

oh and regarding the power tool lithium batteries and ebike batteries - they are actually surprisingly similar. They sometimes use identical cells, and some guys even build ebikes that use power tool batteries as they are (for ease of plugging them in and charging) or rip open power tool batteries to get to the quality battery cells inside.

The big difference is that capacity in Amp Hours (AH). Power tool batteries usually have lower capacities, 2-4 amp hours, whereas ebike batteries usually start at 10AH and can go up to 20 or more. The more amp hours, the more fuel in the tank, so to speak. Also, the more current you can draw. lithium batteries are limited in how much current they can output. Cheap cells are usually limited to 1-2C, where C is the AH rating. So a 10AH pack that is rated for 1C continuous discharge should only be discharged at 10A, with short periods where you can probably draw up to 20A. If you used those exact same cells in a larger pack, say 20AH, then suddenly you can safely draw 20A all the time (still 1C). For power drill packs, if those cells are rated at 1C and it's a 4AH pack, you can only draw 4A. That's the main difference between drill packs and ebike batteries. Other than that, it's about the same thing. Oh, and drill packs often don't have a BMS (battery management system) to monitor the cells during charging.

 

[Modbikemax]

I note all the advice given so far relates to them spending your money and potentially f...ing up your nice bike.
Everyone is good at spending someone else's money.
Go the cheap steel frame route, learn something, then decide if you want to f... up your really nice bike.

It will be a lot cheaper. :wink:

 

[speedmd]

Another pack to look at if it fits is the new GEB pack. GEB-48V11.6AH Dolphin models battery pack http://www.gebattery.com.cn/ If it will fit, you will most likely like this setup. LIPO is possible but some fire risk if not careful.

 

[scfoster]

Got the BBS02 in the mail and was excited to get the installation done. One problem.... the BBS02 doesn't fit

Turns out the bottom bracket casing is too thick (not wide). The distance between the motor housing and the crank spindle is about 5mm too short, so the spindle can't go through the bottom bracket without the motor housing hitting the frame. Oh well.

So I headed down to the bike shop and picked up a Diamondback Apex trail bike that was on sale.

The motor fits just fine. However the bottom bracket is 73mm, so the chain is at such an angle that not all the gears can be used.

I'm willing to grind off 5mm on one side to better align the chain. Has anyone done this or is there some other solution?

 

[Modbikemax]

Thanks for posting that. It's the sort of thing that gets glossed over in the advertising. Chain alignment is pretty important.
I have cut a bottom bracket holder( not sure what you call it) part of the frame down before to get better chain alignment but you need to have some meat to cut off. Carefully mark a line all the way round and carefully cut off with a hack saw. You could use an angle grinder with a 1mm disc but sometimes I prefer hand tools. However there is no going back.
I should mention it was not for this motor.


I would check all your other options first though. For example maybe use fewer gears, with a motor you really don't need the very lowest gears anyway. I would try to get the chain as straight as possible on the gears you will use most which will probably be the first 3.

Told you you would learn something :wink: