Thinking Outside the Shark Battery

Greetings, a couple of weeks ago I bought this bike: https://flic.kr/p/2jHftd1 and yesterday I bought this battery: https://em3ev.com/shop/50v-14s5p-re...ing_wp_cron=1601441773.7520489692687988281250. I can tell you which motor I bought too but my question concerns the battery. I'd like to put it in the open area just behind the seat-tube, in front of the rear wheel. I've got no clue how to hold the battery securely. A triangle bag won't work. I found a squarish bag but it is tiny. Duct tape seems tacky (no pun intended) and anyway this bike is going to be a year round daily driver in the Pacific Northwest. Daily rain after October. Any ideas?

leisesturm said:

I'd like to put it in the open area just behind the seat-tube
[...]
Any ideas?

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Don't put it there?

Rack top is better, easier to protect from splashes. Front of handlebar is better. Hanging from top tube is better, if your knees don't rub across it. Top of a front rack is better.

It's going to take some fabrication. Mine is scrap wood and baling wire. First time around I used fluted polypropylene ("coroplast"), which is very strong but not as esthetically pleasing as scrap wood and baling wire. If you go for something more upscale and need a couple of fancy clamps, t-cycle.com in Portland makes some deluxe stuff.

Make a plate or tray and bolt (seems there is a hole through the tube at the stand) to tube. Use some glue or adhesive to secure the plate on both sides (fill the seam left and right between tube and plate).





Place battery on plate/tray and secure at the top to the seat tube with a U-bolt.

Clearing both the pedals and the chain might be a problem with mounting it there. Chain likely closer than you may think.

Can be done to make a tray to carry it higher.

Longtail bike, nothing wrong with top of rack, or just toss it in a good sturdy saddlebag. Not a flimsy bike pannier, I mean a motorcycle type saddlebag. That worked great for me. Rain protected in that motorcycle type saddle bag.

It’s been common since the beginning of ebikes to mount a battery there, and many frames had been designed specifically for this. All the hardware and accessories for this purpose, is readily available and cheap. You will have to wait until you have the battery in hand though, because it was not designed specifically to fit there.

dogman dan said:

Clearing both the pedals and the chain might be a problem with mounting it there. Chain likely closer than you may think.

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I'd bet money it won't go square in the middle, because of the chain, but slightly offset to the left, it might go. It's about the wettest dirtiest spot on the bicycle though, isn't it?

I'd be looking for a higher mount, more like that bag with the orange zipper (but of course large enough to hold the battery), and strapped up to hang from various points on the frame sounds better than a clamp trying to hold a heavy battery out on a long axis. Consider forces on the mounting not just when standing, but also when on its side or other positions that may happen occasionally.

donn said:

I'd bet money it won't go square in the middle, because of the chain, but slightly offset to the left, it might go. It's about the wettest dirtiest spot on the bicycle though, isn't it?

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I believe that frame uses a 68mm bottom bracket shell, so I agree it can't be centered, since the battery is 81mm. Might work if two chainrings were removed though.

E-HP said:

donn said:

I'd bet money it won't go square in the middle, because of the chain, but slightly offset to the left, it might go. It's about the wettest dirtiest spot on the bicycle though, isn't it?

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I believe that frame uses a 68mm bottom bracket shell, so I agree it can't be centered, since the battery is 81mm. Might work if two chainrings were removed though.

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It is actually a 73mm BB and the rear axle is a modified boost spacing (141mm). I accept that the battery won't/can't be centered though. Good ideas from some, thank you. I really don't want to rack mount the battery because that will ruin its suitability for carrying anything else. It will also place the weight of the battery higher than I would like. It's a last resort option. Motor is a TSDZ2, so a final drive shroud close to the center-line of the bike, regardless of how many chainwheels are removed. As a recumbent rider I am very familiar with T-Cycle. I never thought of looking at their site to see what might be adapted. Thanks to whoever mentioned them. On it ...

Putting a battery there could pose some problems, like the chain and the pedals getting in the way. If you have mid drive that has wider distance between pedals you might be able to get away but a normal crank and pedal width along with the movement of the bike moving the battery then having that hit the pedals while riding is no fun.

I just put my battery hanging off the top tube snugged up close to the seat tube.
I've also placed the battery on top of the rear rack which makes it too top heavy.
Sides of the rack in a bag for lower center of gravity, until you start riding single track trails or bushy areas which can damage the pannier bag.

Mount as low as possible. Center of gravity is king.

Tommm said:

Mount as low as possible. Center of gravity is king.

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The slower you ride, the lower you want the center of gravity. The opposite is also true. Look at motorcycle types: a GP racer has the weight high, while a Trial has it low. I could explain why, but I guess you can find by yourself, now that you have a clue.

MadRhino said:

Tommm said:

Mount as low as possible. Center of gravity is king.

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The slower you ride, the lower you want the center of gravity. The opposite is also true. Look at motorcycle types: a GP racer has the weight high, while a Trial has it low. I could explain why, but I guess you can find by yourself, now that you have a clue.

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Even if that was true, which would completely defy physics, riding an unsuspended cargo bike I don't think he is about to break speed records.

Tommm said:

... [R]iding an unsuspended cargo bike I don't think he is about to break speed records.

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I sure hope you're wrong because that's exactly what I plan. This is going to be the fastest damn cargo bike on the West Coast. Maybe both coasts. To your point, the bar is likely not astoundingly high Unsuspended? Did you see those tires? Vrooom ...

Edit: The T-Cycle site: https://t-cycle.com/collections/all-battery-mount-parts/products/fully-configureable-battery-mount yesss! "Out of Stock" Noooooo ....

Tommm said:

MadRhino said:

Tommm said:

Mount as low as possible. Center of gravity is king.

Click to expand...

The slower you ride, the lower you want the center of gravity. The opposite is also true. Look at motorcycle types: a GP racer has the weight high, while a Trial has it low. I could explain why, but I guess you can find by yourself, now that you have a clue.

Click to expand...

Even if that was true, which would completely defy physics, riding an unsuspended cargo bike I don't think he is about to break speed records.

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He's right. Sport bikes and track racing bikes have their center of mass high and condensed, to make turning around the roll axis as quick as possible (by putting the bike's CoM close to the rider's).

I remember switching motorbikes with my buddy one time. His was a BMW R75/6 with very low CoM, and mine was a big heavy 1100cc Suzuki 4-banger with very high CoM. I couldn't believe how much harder it was to coax his bike around a corner at speed, considering it weighed less than two-thirds what mine did.

For parking lot maneuvering, his was much easier to manage. For scooting around, mine was oh so much better.

If bikes' roll axes were around the contact patches of the tires, your supposition would be correct; lower would be better. But the bike rolls around the combined center of mass of the bike and rider, which is much higher.

Balmorhea said:

Tommm said:

Even if that was true, which would completely defy physics, riding an unsuspended cargo bike I don't think he is about to break speed records.

Click to expand...

He's right. Sport bikes and track racing bikes have their center of mass high and condensed, to make turning around the roll axis as quick as possible (by putting the bike's CoM close to the rider's).

I remember switching motorbikes with my buddy one time. His was a BMW R75/6 with very low CoM, and mine was a big heavy 1100cc Suzuki 4-banger with very high CoM. I couldn't believe how much harder it was to coax his bike around a corner at speed, considering it weighed less than two-thirds what mine did.

For parking lot maneuvering, his was much easier to manage. For scooting around, mine was oh so much better.

If bikes' roll axes were around the contact patches of the tires, your supposition would be correct; lower would be better. But the bike rolls around the combined center of mass of the bike and rider, which is much higher.

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If I needed to carry anything heavy on my sport bikes, the tank bag was the only way to go to not have a negative impact on handling. On the twistys, placing more body weight over the tank provides the best handling as well. I don't recall ever riding slow though. :lol:

I have found that carrying the battery in an under the tt bag like this



to be very effective and am in line with the others that say having weight higher is not detrimental to handling, especially at speed. However if you expect to be reaching high speed averages with a TSDZ2 you might be disappointed. I use them myself on both a mtb and a roadster model and for sure high speeds are not their strong point. Once you get past to 25mph they really struggle, unless of course you are going downhill. You really have to work with the gearing to get it uphill fast too. So mainly I just work within it's limitations for the torque PAS cause it's good for cheap thrills....I find hub motors with big gear ratios and no PAS to be much more effective for speed personally.

Balmorhea said:

Tommm said:

MadRhino said:

Tommm said:

Mount as low as possible. Center of gravity is king.

Click to expand...

The slower you ride, the lower you want the center of gravity. The opposite is also true. Look at motorcycle types: a GP racer has the weight high, while a Trial has it low. I could explain why, but I guess you can find by yourself, now that you have a clue.

Click to expand...

Even if that was true, which would completely defy physics, riding an unsuspended cargo bike I don't think he is about to break speed records.

Click to expand...

He's right. Sport bikes and track racing bikes have their center of mass high and condensed, to make turning around the roll axis as quick as possible (by putting the bike's CoM close to the rider's).

I remember switching motorbikes with my buddy one time. His was a BMW R75/6 with very low CoM, and mine was a big heavy 1100cc Suzuki 4-banger with very high CoM. I couldn't believe how much harder it was to coax his bike around a corner at speed, considering it weighed less than two-thirds what mine did.

For parking lot maneuvering, his was much easier to manage. For scooting around, mine was oh so much better.

If bikes' roll axes were around the contact patches of the tires, your supposition would be correct; lower would be better. But the bike rolls around the combined center of mass of the bike and rider, which is much higher.

Click to expand...

Now to figure out which is relevant for this cargo bike.
Does he plan on leaning the bike at speed or will he be wrestling the bike through the city?
It is also a giveaway imho that all factory emtbs have their battery on the downtube and not the top tube.

I had a quick look and am still not convinced by the high cog argument. I see annecdotes and stories about it but they read more like they are comparing the bike styles that happen to have a high cog vs the bike styles that happen to have a lower cog. Not the same style of bike having one or the other.
The GP bikes can't have a lower cog because they wouldn't have enough clearance to lean as much as they do. But you can bet they are packed as tight and as low as possible. So it is more like a side effect of other factors.
The dirt bikes are also packed as low as they go, without the bottom of the bike hitting the ground at full suspension travel + some margin for a rock. So it looks higher but in reality is low as possible.
A cruiser neither has to lean heavy or have a big travel. So it has a very low cog, because that's the lowest they could put it.

Neither of the bikes feel like they do as a result of their cog alone, they feel like it because of the head angle, wheelbase, weight, weight centralisation and cog.

The only test I would give any weight to is picking multiple styles of bikes and putting a 40lbs lead weight to the very top and then the very bottom of them, and letting a test pilot see the difference.
But to me it looks like every type of bike has it as low as possible for the given circumstances, including emtbs.

Should clear his pedals fine, and above the chain should still be plenty low for the parking lots. Its just not likely to clear the chain and or crank if you put it at the very bottom. Another cargo bike I built had two battery trays built into the frame. They both went in just above the crank, so the frame metal cleared crank and chain. That one handled so good, but it burned in the fire.

Iv'e been riding low cog scooters for years and now a bmw R bike, and they do handle different. Simple solution though, learn to counter steer and they need no coaxing to corner just fine at any speed.

But yeah, you don't just knee over a scooter, no tank, and low cog. I love the way the R bike handles on my kind of road. 10 mph hairpin corners, enter em at 20 mph where the low cog works good, exit at 40. On the faster mountain roads I don't feel it corners poorly, but I'm not racing, nor looking to hit an elk at 70 mph. Doing the 191 in Arizona today

Tommm said:

MadRhino said:

Tommm said:

Mount as low as possible. Center of gravity is king.

Click to expand...

The slower you ride, the lower you want the center of gravity. The opposite is also true. Look at motorcycle types: a GP racer has the weight high, while a Trial has it low. I could explain why, but I guess you can find by yourself, now that you have a clue.

Click to expand...

Even if that was true, which would completely defy physics, ...

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OK. I see that you have your mind set and won’t search for the truth?

Lever physics is simple enough?

Riding slow, or even standing still, there is an advantage to stand upright and to have a large lever effect on the bike’s weight. Low COG is exactly that. That is because you then need to move the top of the bike a lot to transfer a given amount of weight. This large range of movement is giving precision over the amount of weight transfered, and a delay that is helping the rider avoiding over-correction when moving the weight in order to maintain balance at low speed or standing still.

When riding and maneuvering fast, there is an advantage to transfer weight with minimal movement and to adopt a tucked position. You want the shortest delay, thus the least lever effect on the bike’s weight. High COG is exactly that. Racing a GP bike, you first steer a bit left to turn right, to help initiating the weight transfer of a bike on which you have almost no lever effect. We do it naturally too at lower speed on light weight bikes but it is then a counterintuitive reflex.

Now about bike types. A big highway cruiser has low COG for the reasons that:
-It is heavy, thus would be hard to maneuver at low speed or stopped.
-It doesn’t need to have reactive handling. Quite the opposite, it has an advantage to have a delay because of the lazy riding position.

MX racers have a huge and high gas tank, for a short race after all, and one that requires light weight. Why is that? We want to be able to tune the height of the COG, with the amount of gas in the tank. That is because some tracks are faster with lower jumps and the advantage of high COG is more important than the advantage of lighter weight in high speed aggressive maneuvering.

On the opposite, Trials have a very small gas tank that is very low. All the bike is designed for the lowest COG, because you need a lot of lever effect to place the bike with precision, in a sport that is practiced at very low speed and penalizes every touch of a foot to the ground.

Tommm said:

on the downtube and not the top tube.

I had a quick look and am still not convinced by the high cog argument. I see annecdotes and stories about it but they read more like they are comparing the bike styles that happen to have a high cog vs the bike styles that happen to have a lower cog. Not the same style of bike having one or the other.

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You should try correcting your line when taking a corner a triple digits, and you'll be convinced.