jonescg's NEW electric racebike BUILD thread!

[Frank]

Nice update Chris. I'm in the process of (slowly) building a 60S13P battery for my street-legal Hayabusa and land-speed bike using the 2170 format Molicels. I experimented with the cells and welding last year for a 20S5P replacement pack for a friend's scooter with some success. I'm building four sub-packs/blocks, mostly for ease of handling. Assuming this works out I'm also contemplating a 96S8P build for another race bike.

Good to see you back online!

 

[jonescg]

This weekend, we sort of got the band back together

A long-time mate of mine who helped out at the Mallala and Queensland Raceway rounds of the eFX series was in Perth for the weekend. Dan Evans looked after the bike and us, whenever we were in town. While he was over, we caught up with Pottz (Danny Pottage) who first steered Voltron to victory - long before it ever turned and stopped properly. Also, we watched Jack Miller take the Motegi GP win. Great weekend all round!

We were drinking beers kicking tyres in the shed, and entertaining options for the bike. It's going to be about $6000 for a new battery, but as discussed above, it's going to be a heavier battery at 70 kg, but twice the capacity at around 12.2 kWh. The alternative is to go for a 4p 168s pack which is only 9.8 kWh and weighs 56 kg, but being a Molicell pack, probably only good for peaks of 180 amps (110 kW-ish).

So the bike needs a diet, and wheels are a good place to start. Carbon wheels prevent us from racing in most classes, but given the weight constraints we face, it might get a concessional admission. If we have less power to start with, spinning up less rotating mass is a good idea. We have known for a while now that the rear wheel is not in line with the centre of the bike, which probably explains why most anticlockwise circuits were rough on corner exits. So we found a way of moving the wheel across about 10 mm and getting it back onto the meat of the tyre at lean. I'll have to get these fabricated soon, but so long as it doesn't involve messing with the wheels we can put lighter wheels on later.

I'm pretty sold on cylindrical cells now, as the pouches were just so easy to compromise, and they never lasted all that long. I guess if money were no issue we could build two batteries - a 10 pack and a 12 pack.

 

[Danny Mayes]

Go Chris, cant wait to see it back on the track. Shout out if you need some help, happy to support if I can.

 

[jonescg]

So this is the current situation with the rear wheel.

The rear wheel and brake assembly is from a GSXR1000 so the swingarm needed to have a slot built into it to capture the brake calliper. The centreline of the rear wheel is about 15 mm off centre from the middle of the bike, so we need to gain 15 mm by moving the wheel to the left, and filling the space on the right. Unfortunately, you can't go leaving the sprocket and brake disc where it is so the whole calliper will need to move to the left by whatever we can gain, and the tongue on the calliper will need to be modified so that it can reach into the groove.

Just by moving the plain spacer across to the other side, we gain 5.9 mm.


We also have the opportunity to machine the two wheel bearing spacers so the left one is about 6 mm shorter, and the right one is 6 mm longer. We might be able to build up a bead of weld on the brake calliper mount so that it reaches well inside the groove on the swingarm.


This obviously moves the chain run too far to the left, by potentially about 12 mm. We can move the front sprocket about 4 mm to the left without it fouling the frame, although it's getting further out on the driveshaft which is never ideal. We have heaps of meat there - it's 44.45 mm in diameter.

But this will mean its time for a super custom sprocket, one where the teeth of the rear sprocket are off-set inwards from the face which bolts to the wheel. We would need to do this with steel I presume, as alloy might be a bit ambitious. We're not going to go smaller on the chain - 600 Nm of torque needs as much chain as you can muster!

 

[Solexelec]

Hi for your caliper, you can also machine a spacer that will shift your rear disc to the right and thus find the original fixing.

for the rear sprocket, I have already seen rims reworked to remove an extra thickness.

your rim moves but not your accessories, remains to be validated if it goes with the tire.

 

[jonescg]

Hmm, I might have avoided this in the past because the shoulder bolt head clearance is not ideal, but I reckon we can make something of it. The Suzuki OEM bolts are a bit special - M8 thread, 10 mm diameter shoulder, but the length of the shoulder is 7 mm. And the head is a flattened pan, presumably to clear the calliper mount. I can always turn them down to fit, I guess.

But yes, not modifying a cast aluminium part with heat is a good move.

 

[Frank]

I've machined a sprocket carrier before to move the sprocket back towards centerline. It might be worthwhile picking up a scrap one at the wreckers or evilbay and seeing how much you might gain w/o compromising integrity.

 

[jonescg]

I've machined a sprocket carrier before to move the sprocket back towards centerline. It might be worthwhile picking up a scrap one at the wreckers or evilbay and seeing how much you might gain w/o compromising integrity.

I'd be interested to hear more about this, Frank. I'm thinking steel is the better material, and obviously limits us to this size or larger, but 6 mm might not be too hard to find. The current chain run is ~8 mm well clear of the tyre so theoretically we've got the numbers to make it work.

 

[Frank]

I can't figure out how to embed it, but here's a link to a GS500 sprocket carrier that I was playing with to make the GS500 swingarm and wheel work with a T500 in the T500 frame. You can see holes where we were starting to break through. Ultimately the c/shaft sprocket was shimmed out a bit and a different sprocket carrier turned down to make the chain line up (don't forget about rear tire clearance!). I'm running a 520 chain and turned down a 530 sprocket to get some more offset but didn't need to use it.

I can't remember how much material was removed here but I've found notes indicating we were aiming for 5/8". We never got there but made things line up by a combination of machining somewhat less than the 5/8" and moving the c/shaft sprocket out. My numbers were "tape measure estimates" but I'll bet this carrier had at least 3/8" taken off it. YMMV but it might be worth playing with a scrap carrier to see what you can get out of it.

https://flic.kr/p/2nPgrfn

 

[jonescg]

Interesting - the break-through looks a bit sketchy, but I might not need to mess with the sprocket carrier if I can get an offset sprocket to suit. It's being raced occasionally, so it's not like I'll be changing sprockets often.

The hub proper is 160 mm diameter, so it might be possible to get something which bolts onto the carrier in the usual way, but allows the sprocket to hang past the hub in the inside.

 

[jonescg]

So it seems the 6.0" rim width of the K9 GSXR1000 rear wheel is the problem. The hub is physically bigger than the previous 5.5" rim width of earlier models, which means there's not much sprocket mount to machine into before you hit the hub anyway.
So here's an idea - an off-set (or should that be an in-set) rear sprocket which can clear the 160 mm diameter wheel hub, but still have enough meat to handle the forces.




I've not drawn the teeth on the sprocket (as that's rather difficult to do) but you can sort of get the gist. It wouldn't be cheap to machine, but a 5 axis CNC could probably make this out of T6 alloy?

 

[Frank]

Sounds doable as long as the chain won't hit the tire. Is switching to the narrower wheel an option or does that compromise tire size and mounting too much?

 

[jonescg]

There was 8 mm of clearance originally and I've got another 4 mm or so on the front sprocket.
The 190 tyre on a 5.5" rim was okay, but we needed more grip on exit. Just imagine what it will be like when the wheels are in line!

 

[jonescg]

Had a crack at drawing the sprocket - think I did OK.



The thinnest part in the section is 6 mm, which is probably not ideal. If I needed a bigger rear sprocket it wouldn't be an issue, but as it is, 37 teeth is already high speed wheelie country.

Might need to get this made out of steel?

 

[j bjork]

I was going to say that it looks like there is room for more material around the bolt heads if needed, but I just realized that it is the inside and not the bolt hole side..
Do you plan to have it cnc milled, or cut out and finish it on a ordinary lathe?

 

[jonescg]

Probably 4 axis CNC, But its the sort of job you could finish on a decent lathe.
I'll try and get a section profile image up...


Not great, but I'm not sure how much more radius I can put on the sprockets inside edge.

 

[jonescg]

Hmmm, depending on how much compression the cush drive takes, I might be able to add a bit more fillet.
It sits proud a few mm - may be enough to clear the inner recess?

 

[jonescg]

So the spacers all worked out - just need to get the new sprocket made. If I move to magnesium or carbon wheels the weight savings will offset the extra mass of a 5p battery.
On the battery, I'm torn between making a bike that is lighter, but has less power, or a bike which is heavier and has almost the same power. A 168s5p battery is possible, but would have a grand final mass of about 70 kg, which is an easy 14 kg heavier than the 6 kWh pouch cell pack. But double the capacity!

I can probably take a power hit, because a fast bike is a light bike. But considering the sag on these cells will be higher than the sag on pouches, I'll probably be looking at pretty much the same range with 9.8 kWh as 6.3 kWh.
It's also a bit of a squeeze to get the 12 kWh battery in there. Maybe I should drop to 9.8 kWh and be done with?

 

[SlowCo]

On the battery, I'm torn between making a bike that is lighter, but has less power, or a bike which is heavier and has almost the same power.
I can probably take a power hit, because a fast bike is a light bike. But considering the sag on these cells will be higher than the sag on pouches, I'll probably be looking at pretty much the same range with 9.8 kWh as 6.3 kWh.

Comparable with the difference between 600cc and 1000cc bikes. It comes down to preference and the type of tracks you'll ride with it.

 

[jonescg]

Yeah, the kicker for me was, if I opt for the lighter, shorter-range, but less powerful option, I might as well swap the motor out for a lighter motor which saves 10 or 15 kg. Plus, even if we did get the bike turning well on a short range battery, all the stewards need to do is add two laps to the race and we're pre-ordering a DNF.
So as much as it pains me, a heavier bike with 140 kW and more range is the solution, I think.
Then I need to find some lighter wheels.

 

[jonescg]

Welp, I dropped some coin on 850 Molicells. This is enough to build a 12.5 kWh battery. If I minimise the potting to just the sides of the battery, it will weigh in at about 70 kg. Which is a lot more than I like, but the range will make it a viable track bike with any major class of Australian club racing (up to 22 km). If nothing else I can enter it into the TT in 2024

 

[amberwolf]

What does the potting have to do for you?

Maybe you could use foaming silicone like this:

Purchase Soma Foama Silicone Foam

Soft two-component silicone foam used for a variety of industrial and special effects applications.

www.reynoldsam.com

Just keep in mind you have like 30 seconds to do something with it once you start mixing the two parts. (I wish it was longer, since I'm not very fast at mixing/pouring/etc, but it still does what I need it to in my non-ev projects)

Soma Foama® 15 & 25 are soft, two-component platinum silicone flexible foams that are versatile, easy to use and can be poured into a mold or over other surfaces. Compatible with platinum silicone rubbers, cured foam has high heat resistance (up to 350°F / 176°C), are water resistant, UV resistant, and resists oxidation and ozone degradation. They can be used for a variety of industrial and special effects applications including making foam filled appliances, padding/seat cushioning, orthotics/orthopedics, potting and encapsulation of electrical circuits and vibration dampening.

 

[riba2233]

Welp, I dropped some coin on 850 Molicells. This is enough to build a 12.5 kWh battery. If I minimise the potting to just the sides of the battery, it will weigh in at about 70 kg. Which is a lot more than I like, but the range will make it a viable track bike with any major class of Australian club racing (up to 22 km). If nothing else I can enter it into the TT in 2024

What cells did you get?

 

[jonescg]

What does the potting have to do for you?

Maybe you could use foaming silicone like this:

Purchase Soma Foama Silicone Foam

Soft two-component silicone foam used for a variety of industrial and special effects applications.

www.reynoldsam.com

Just keep in mind you have like 30 seconds to do something with it once you start mixing the two parts. (I wish it was longer, since I'm not very fast at mixing/pouring/etc, but it still does what I need it to in my non-ev projects)

Potting is mainly to keep the cells snug in their capture plates so they don't vibrate themselves to pieces. But also waterproofing/corrosion resistance, and a bit of thermal uniformity.

I hate hate hate short pot-life polyurethanes. Like you I'm just too slow at doing the mixing and pouring.

 

[jonescg]

What cells did you get?

Molicell P42As. They seem to be a good combination of energy density and power, and they aren't unobtainium like P45Bs.