Ultimate E-Bike Battery Box???

[mainsource]

Guys, why dont we see more of this battery box approach to road-going (non off-road) ebikes?? Can it claim to be headed in a useful direction? It happens to be my personal design... This one is deliberately setup to be particularly low, but ground clearance is obviously adjustable during the design phase.... Comments please!

 

[adrian_sm]

You might want to add a bit more clearance for front suspension travel.

I was chatting to John at Stealth Electric bikes a while back and noticed an early prototype that had a lower battery mount location towards what you have. He ended up putting the weight higher to improve the handling, notably mentioning the ability to power wheelie which is important for off-road riding to get over logs etc.

I also vaguely remember another discussion around having the weight too low making the bike twitchy/wobbly or something about how well it changes direction. Hopefully someone more knowledgeable than me will pipe up.

 

[Drunkskunk]

Neat design, But either that box has to move with the front wheel, or the first hard bump will slam the tire into the box. If it moves with the wheel, its partly counted to the bike's unsprung weight, and that has a negative effect on handling.

The other reason you don't see this design more often, is the weight would be too low. getting the COG low is good on low speed bikes, or things that don't lean into corners like cars. but on a high speed bike you want the weight up higher. There is a reason why ICE street bikes put the motor up high under the tank in the frame, and route the exhaust under the motor, its because thats the idea place for the weight.

 

[mainsource]

wheel travel has already been tested - no problems there.. the box is located such that the wheel moves up into its ideal arc location on a hard jounce... i also do not plan on going soft on the suspension... regarding too low a CG, my point of view is, that unlike a heavy motorcycle several times the weight of the rider, the upper body weight of the cyclist should more than balance out the overall center of gravity. this, since the amount of lipo batteries required come no where near the upper body weight of the rider. further to the point of twitchy; that's how my regular commuter bike feels with overloaded saddle bags - especially when the bulk of the weight is located up high (towards the top of the bags that is).

 

[mainsource]

the proof of the pudding is in the eating - and i am having this one for breakfast in two weeks!!

 

[Ykick]

Ground clearance reminds me of my kickbikes and it doesn't take much to high center. Video of your breakfast please!

 

[dogman dan]

Sooner or later buddy, you're going over the bars. One good chuckhole you don't see, that front tire's gonna jam, and wheeee!

Would be fine on a solid fork, of course.

 

[SamTexas]

Looks interesting. Do you have a bigger picture?

 

[ohzee]

Yea i was thinking the same thing.. looks neat , but the pic makes it hard to see what's what.

 

[neptronix]

Why not just mount the batteries in the center triangle with something like the falconEV bag?

http://endless-sphere.com/forums/viewtopic.php?f=4&t=29211&p=527575

Or replicate that in aluminum..

Best weight balance ever. Feels really natural.

 

[John in CR]

As long as you avoid the pregnant guppy look, is aerodynamic instead of the air brake pictured, is strong enough to protect the battery, and is absolutely waterproof, then sure why not. Avoiding the (IMHO) ugly guppy look while having sufficuent curb and suspension wheel front clearance is your real challenge.

BTW, you aren't seriously leaving the triangle (the ideal location for a battery) open just to hang it down there, are you?

John

 

[mainsource]

i am seriously leaving the triangle open... aesthetics is equally important on this build... my fork has stiffness adjustment and a lockout if needed... i always ride stiff cuz i used to ride road and like my bike ready for any challengers that may think i am a pushover... my current commuter is setup for just 1 1/2 inches of travel... my experience with different motorcycles confirms that my personal preference is for the lowest CG possible and this is the objective of my build.

 

[mainsource]

btw the box is just mocked-up in the posted pic... i had it completely mounted today with an upward tilt that matches the arc of the wheel at max jounce expected for typical road riding.

 

[dogman dan]

Brilliant, get a bike with a shock fork, then ride it with the fork locked out. Or bet your collarbones on "expected" fork travel.

Nothing wrong with it, if you redesign the box, eliminating the portion that curves above the wheel. Lop it off about where the A in Raliegh is on the frame, then the fork can travel if it needs to when you don't see that pothole in time.

I do understand about fork travel. I dirt ride, and see how a good fork only uses half it's travel most of the time even when riding rough trails. But once in a blue moon, you do nearly bottom the thing out. What I mean, is one fine day that car runs you off the road, and it's hop that curb or die. Wouldn't you rather hop the curb and live, instead of stuffing the wheel and going flying. On that day, you'll be very glad your front forks had some travel dude.

But don't listen to us, we're so new at this.

 

[mainsource]

am with you dogman!... the design does not absolutely need the portion that arches over the front wheel and i will give serious consideration to removing this feature...

 

[Evoforce]

You will definitely need to be able to go over curbs that are not depressed at different times in your riding experience if it is built too low it will not get over a curb you will find yourself in a tough position. Some types of speed bumps could also pose a problem.

 

[amberwolf]

If I were building a box like that on a suspension bike, I would most definitely first compress the suspension *completely*, before measuring the space required for wheel movement. Then I would leave another extra centimeter or so in case the fork flexes back during braking or impact, just in case.

I can't clearly see your shocks in the pic to tell if they are pneumatic or not, but if they are you could let all the air out to make it easier to fully compress them for this measurement. Then add clamps between the handlebars and the bottom of the crown, compressing until there is no more possible compression of the fork (not just until it's hard to compress, but until it is physically impossible to continue). You could use very large hose clamps, or very big and strong zip ties, (preferably at least a pair of the half-inch-wide ones on each side, in case one breaks or slips).


If you don't allow for *complete* compression of the shocks, then it's likely that one day the predictions of others before me in this thread will come true, and you're not going to enjoy the results.


Remember also that when the shocks are completely compressed, you need to have clearance on the box's bottom forward area for whatever compressed it--right now, even if the box were adjusted to ride higher by the difference in spacing between it's top and the downtube, it looks like the box would strike the ground during full shock compression.



I also would recommend using the triangle for your battery, as in my experience handling is notably better with the weight at most along the axle line, or above it. Depends on the rest of the bike's configuration. The farther away the weight of the bike is from your own, the harder it can be to pivot that mass using the pendulum effect (where your mass is the pendulum end, and the bike is everything between the pendulum pivot (contact patch with road) and the pendulum itself). If your weight is a lot higher than the bike's, it'll be easier, but if you are typical to light weight then it takes more effort by you to use body english to control the bike (which you do whether you realize it or not).


Other than those two things, it looks like an interesting plan, and I would like to see it's finished state. I am interested to see how you install bearings (and which ones you use) on the crankshaft-mounting-point holes in the battery box, and how you tie it to the downtube at the front and along it's length.

 

[mainsource]

thanks amberwolf... more pix coming soon.

 

[dogman dan]

It was awfull pretty though, with the curve. Still cool to have it, but more as a fender than a cavity to hold more battery. With more clearance then of course.

I hate to say do a complete redesign, but it might be cool to put some of the battery as planned, and have more box with the rest above the downtube in the triangle.

 

[mainsource]

funny to hear you say use the triangle in addition to the area below for even more battery dogman! even though my original plan was to do just the one box at the bottom of the frame, i pondered today; why waste the triangle space?... consequentially, i started work on a second battery box for the triangle.

 

[mainsource]

thanks amberwolf, for the analogy of the pendulum... however, i need you to think for a moment: the fulcrum of that pendulum is actually where the tire contact patch meets the road, not at the axle center-line as was earlier mentioned! if you are in agreement with me on this point, you would then conclude as utter rubbish, the notion from some earlier in this thread, that moving the battery CG closer to the fulcrum would result in twitchy countersteer action. take the same battery CG, locate it vertically to the top of a 10 foot pole and attach it to the bike...then tell me what do you get?? the closer a mass moves to a fulcrum, the more reduced are the turning moments, ultimately achieving a value of zero (no influence or neutral impact) - meaning in this case: a steadily reducing ability to have an effect on the countersteer dynamics of the bicycle!

 

[mainsource]

pls find a closer image of battery box attached

 

[amberwolf]

I can't see in either pic the bearings or bushings you must be using on the crankshaft (to allow the pedals to turn without wearing thru either the shaft or the box mount). How do you have it attached?

 

[dogman dan]

Clearance does look a lot better in that pic. How hard would it be to rebuild it, so you have 1 inch more? That would do it I bet.

For ideas on where to put the CG, look to motorcycles where it's been really well figured out for years. It depends on what kind of riding you are doing. For 1 mph or less riding on trials courses, they put the CG as low as possible. But once you are making turns at 25 mph or more, the CG moves up to about where the knees on the rider are located. Maybe even higher with a full load of fuel.

But I'm not saying having the battery weight low will be a problem at bicycle speeds, say 25 mph or less. It for sure will be less of a problem than locating that weight real high on a rear rack.

I've ridden an EVG bike, which had a lot of weight in two lead batteries built into the downtube. It did handle different, but I wouldn't say it was bad handling. In that case though, the weight was not below the crank. Half in the triangle and half below the crank should work real good.

 

[mainsource]

amberwolf: about the bearings, the holes in the case are about 10 thou proud of axle diameter and were used to properly locate the case before permanent mounts were fabricated. now that i have the permanent mounts in place, the holes would be further clearanced to avoid interference with the axle.

dogman: i have started fabricating the triangle case due to input from you and others on the forum... now i think its the only proper way to finish this project! notwithstanding my occasionally arrogant tone (in defense of this project) - i want to say THANKS for all the contributions that came in!