YZF 2007 Electric conversion

BenBenBen

1 W
Joined
Jun 18, 2022
Messages
51
Hi everyone,

I'm Ben from France, new on this forum, and I started to convert a YAMAHA YZF 250 2007 to electric to make myself a good electric enduro bike and go riding on the weekend.

I bought a QS138 90H motor for this built, and plan to:
- Control it with a Silixcon SL
- Feed it with a 20S15 (or 16)P MOLICEL P42A pack so 4 to 5 kWh

Idea is to get about 22kW peak, as it seems to be a classic with this motor setup.

My first point is about transmission. I calculated that a (more or less) 5.5 gear ration between motor and rear wheel would be cool to reach 90km/h at 4000RPM at the motor and have good torque for enduro.

Option 1: Use the original 14T 428 type sprocket of the motor and use it with a custom 76T 428 type sprocket at the rear wheel.
Advantage: easy motor mount, compact design in the frame area (more space for batteries)
Disadvantages: weak chain (428), verry large and custom made rear sprocket

Option 2: Make a 2 stages transmission using the 22T original belt sproket of the motor with a 44T pulley and then a YZF standards 520 14T and 49T sprokets for the second stage, with a custom built axle in the middle.
Advantage: more tunning possibilities, only "on the shelf" belt, sprockets, chain, strong 520 type chain etc...
Disadvantages: complex motor mounting, need for an expensive custom middle axle, usiong more space in the batteries area.

According to your experience, what's your opinion about this choice?
Other question: Do you know which belt standard is used on the original 22T belt sprocket of the QS138 90h?

Thanks a lot in advance!!!

I already 3D printed the QS138 motor, and it mounts verry easily in single stage transmission position, only by re-drilling the bracket hole to 16mm, making a set of simple sheet metal brackets and grinding the frame a tiny little bit.
 

Attachments

  • IMG_20220618_172021.jpg
    IMG_20220618_172021.jpg
    3.5 MB · Views: 1,472
  • Capture d’écran 2022-06-18 173015.jpg
    Capture d’écran 2022-06-18 173015.jpg
    61.2 KB · Views: 1,472
5,5:1 will be a disaster.
You need at least about 8:1 to get good torque on the rear wheel.
That is my experience with a little over 500 phase Amps.
If you have a lot more maybe you can get away with higher gearing.

I would just go with the v3 with built in reduction. With that you can get almost any gearing you want in the end.
Why 4000 rpm?
 
Hi J Bjork,

Thanks for you reaction! I took 4k rpm as calculation basis cause it's given as the max speed of the QS 138 motor under 72V WO deflux, according to the "data sheet".

Aslo, I watched videos of the guys from ELMOFO that made some conversions based on Yzf Yam and CR Honda, same motor, and with a 76T rear sprocket (that they make and sell as spare parts by the way). They also sell complete kits, for about 7k USD. And from what I've seen, it didn't looked like missing torque with a Bac 8000 controller from ASI and a 21S ~4kwh pack. But that only videos of course, I've never seen one for real, and never tested one of course. Have you seen those bikes?

Regarding the V3 QS with integrated gearing, I didn't took this one cause it's rated 1kw lower than the 138 90H version. You think they can reach about the same peak power?

Ben
 
larsb said:
No, for sure not. 90h motor will have about 90/70 advantage since peak power scales by peak torque which scales by stator width for the same stator.
that's what I had in mind, and it seems logic!
 
I missed that you went for the 90h.
Still, if you go 5,5 gearing and 30% more torque compared to my 8,6:1 gearing:

5,5/8,6 =0,64x1,3=0,83

If my calculations is correct that would mean 17% less torque at the wheel.
If you can push the motor to 50% more torque you are still behind with 5% at the wheel.

To get to my 8,6:1 I have 10t front and 86t rear, both custom made. That rear sprocket is annoying, it gets dipped in mud and sand often. Sometimes it hits rocks too..
 
Got it! I took a moment to read all your thread on the KTM, and things looks more clear to me now.

Even if I still wonder how they do on those Elmofo bikes. Maybe they just looks better on video than they feel ridding it...

This gear ratio stuff looks like it was a real head scratching on your built!

I really hesitate to switch to a 2 stages design with strong and "easy to find" 520 part on the secondary.

It doesn't make me afraid technicaly, I've already done it on a 10kw golden motor for a PGO buggy (attached pictures), but the point here is the volume... And I really want to stay on my 5kWh pack idea...

If you had to start your KTM from scratch again, would you stay with this giant 428 sproket design of rather go with 2 stages?
 

Attachments

  • poulie 1.jpg
    poulie 1.jpg
    51.3 KB · Views: 1,401
  • poulie 2.jpg
    poulie 2.jpg
    48.7 KB · Views: 1,401
  • poulie 3.jpg
    poulie 3.jpg
    61.5 KB · Views: 1,401
  • IMG_20220223_200526.jpg
    IMG_20220223_200526.jpg
    3.7 MB · Views: 1,401
  • Capture d’écran 2022-06-19 115619.jpg
    Capture d’écran 2022-06-19 115619.jpg
    41.2 KB · Views: 1,401
Ok I made a few simulations this morning to compare the volume taken by both solutions with a 1:2 first stage (22T / 44T).

Clearly, the 2 stages takes to much space and will reduce the pack from at list 1kWh (pictures attached). I'll make the "range" choice, rather than mechanical elegance...

So I'll go for a direct 428 transmission, and we'll see later how big my rear sprocket will have to be. I'll laser cut several sizes on cheap alu, from the 76T to 90T just for testing, and make a strong version when decided what's the best compromise.

Next steps:
- Wainting for the motor to arrive
- Mount it
- Test it with random 20S pack to validate mechanical integration
- Start the battery pack design
 

Attachments

  • volume comparison.jpg
    volume comparison.jpg
    83.9 KB · Views: 1,397
BenBenBen said:
Option 1: Use the original 14T 428 type sprocket of the motor and use it with a custom 76T 428 type sprocket at the rear wheel.
Advantage: easy motor mount, compact design in the frame area (more space for batteries)
Disadvantages: weak chain (428), verry large and custom made rear sprocket

If QS did not increase the quality of their sprockets enormously, I would strongly recommend NOT using their sprockets.
What they sent me with my QS138/70 was just garbage. It was sitting on the shaft totally loosely.
Now I am using a 520 11 teeth JTF sprocket in front and a 70 teeth custom made sprocket on the rear, and I think it's quite good.
(or would be good, if the controller wouldn't act up, as it actually does)
 
Elektrosherpa said:
BenBenBen said:
Option 1: Use the original 14T 428 type sprocket of the motor and use it with a custom 76T 428 type sprocket at the rear wheel.
Advantage: easy motor mount, compact design in the frame area (more space for batteries)
Disadvantages: weak chain (428), verry large and custom made rear sprocket

If QS did not increase the quality of their sprockets enormously, I would strongly recommend NOT using their sprockets.
What they sent me with my QS138/70 was just garbage. It was sitting on the shaft totally loosely.
Now I am using a 520 11 teeth JTF sprocket in front and a 70 teeth custom made sprocket on the rear, and I think it's quite good.
(or would be good, if the controller wouldn't act up, as it actually does)

On the 138-90H I baught, I didn't choose the spline shaft option, but the conical with keeway. For for sure, they won't be any play there. Let's hope that the ttoth quality will be okay!
 
BenBenBen said:
If you had to start your KTM from scratch again, would you stay with this giant 428 sproket design of rather go with 2 stages?

I would defiantly went 2 stage now, I have thought about changing to a v3 motor.
It wasnt avalible when I built the bike, I dont think the 90h was either.

But I dont think it is worth it for me, the plan is to ride the yamaha instead when I am happy with the performance.
 
Got it,

If I had the same YZF that your got, I would probably go for the same kind of 2 stages (just smaller motor 138-90H). But in my case, it's the previous version and the available volume for batteries is a lot lower, due to the upper center beam that you don't have.

So, instead of the mechanical elegance, I'm probably going to make the "range" choice and stay on my 5 kWh idea. I'm using 21700 cells, horizontally and on 2 layers. So I'm verry flexible about the shape of my core pack and I should be able to fill most of the available space, even arround the motor.

Now I'm lasercutting a bunch of 428 rear sprockets in cheap alu, from 76 to 90T, and I'll make a strong one in 7075 grade after testings.

Aslo, I made a little simulation, and a 13T 428 sprocket should mount on the QS138-90H conical shaft. But 12T won't work, because of the to big diameter of the shaft. Or, at list, not without reducing the 38 diam of the centering section of the part (QS original drawing attached). But I'm afraid reducing this area creates a (too) weak point arround the keyway groove.
Other problem is that they only sell the 14T version. I'll have to make the 13T myself.
 

Attachments

  • sprocket sizes.jpg
    sprocket sizes.jpg
    127.1 KB · Views: 1,343
Hi everyone,

I made a few calculations, and I'm getting confused...

To have a reference point, I looked at the gearing ratios, speeds and torque on the original setup of the bike (ICE Yam WRF 250 4 strokes with 5 gears gearbox).

When I compare max speeds and torques, I figure out that, even in the worst case which is 14/76 teeth in 428 chain, I got more than twice the torque (at the rear wheel), that the original enduro bike on first gear @8500 rpm in factory setup which looks a lot more than enough for how I plan to use it!

@Bjork, I added your setup for comparison

Maybe some of my inputs or formulas are wrong? Or did I missed something?
 

Attachments

  • ratio.jpg
    ratio.jpg
    131.4 KB · Views: 1,328
Shit your right!!! It's a 1:3 ratio on this one.

I Update.

It looks more logic now. But still surprising.
 

Attachments

  • ratio.jpg
    ratio.jpg
    138.3 KB · Views: 1,320
BenBenBen said:
It looks more logic now. But still surprising.

how can be logic that in first gear the WFR reach 117 km/h ??? :lol:

Your calculation of the WFR are wrong - you need to multiply (not jut add) the gear ratios - You'll end up with approx 815 Nm in first gear.

Believe or not, anything less than 500 Nm will not make your bike funny to drive
 
Okayyyyy!!!!!

No I see my problem since the begining, I was addtionning the stages in "multiple stages transmission" setups instead of multiplying them... :confused:

So here the final calculation, and I makes perfectly sense, unlike all the others!

Good news is that on the 2 stages ratio I simulated before, I had a 1:2 ration on the primary, but don't need so much finally. So the big pulley (44T) doesn't have to be so big, and take so much space. I'll see how it looks with a smaller one.

Good figures attached.

Thanks a lot for your clarifications!
 

Attachments

  • ratio.jpg
    ratio.jpg
    138.3 KB · Views: 1,309
frostnova37 said:
I am doing a similarly spec'd project with a DRZ-400SM. What made decide to go with the SL controller and how much does it cost?

Well, I choosed le Silixcon SL for several reasons:
- It's extremely compact compared to competitors @ equivalent perfs
- I love the design and the specs, at list on the paper. As I love all the products those guys make!
- I want to test, characerise it and learn how to fine tune it for professional reasons
- I had the opportunity to get acccess to one

But If I din't had the contacts and professional needs, I would probably go for an other one cause it's verry complicated to source for private individuals. Price is arround 1k€ id I remember well for a unit sample. Silixcon have a limited production capacity, especially in those complicated times of components sourcing. And they are not focus on isolated conversion projects, but more on interesting OEM vehicles with volumes and good communication feedback.

About transmission. I took a nigh to think about it, and you guys convinced me to go with 2 steps.

I started to draw a concept and here how it could look like. I took a lot of inspiration on Bjork YZF concept, but adapted it to fit with my tools, 138-90H motor and older bike. I'm not a big fan of 428 chain first stage because of noise and maintenance, so I went for a 20mm 8M belt. And then a 520 chain secondary. Still got to find a way to tune the tension, and they are many surfaces and details to finalize to have a good mechanical design, but the main lines are there.

The plan is to start with a 1:7.27 ratio, and go for larger rear sprockets if required.
 

Attachments

  • reduc1.jpg
    reduc1.jpg
    159.4 KB · Views: 1,269
  • reduc2.jpg
    reduc2.jpg
    209.8 KB · Views: 1,269
  • reduc3.jpg
    reduc3.jpg
    73.3 KB · Views: 1,269
  • reduc4.jpg
    reduc4.jpg
    59.3 KB · Views: 1,268
  • reduc5.jpg
    reduc5.jpg
    39.3 KB · Views: 1,269
Elektrosherpa said:
BenBenBen said:
I'm not a big fan of 428 chain first stage because of noise and maintenance, so I went for a 20mm 8M belt.

I would think again if noise is such a big issue in relation to durability and easy maintenance of a chain...

Did you have bad feedback concerning that kind of Belt drive first step?

The thing is that I'll need a tensioning system in both situations. And, As I won't be able to slide the motor on the plates ( 6 screws on each side and no room for slots), I had in mind to use some automotive belt tensionners, and I found one in 50mm diameter with a exantric setup that could fit and make the tensionning strong and relatively easy.
 

Attachments

  • tensionner Belingo 2.0 HDI.jpg
    tensionner Belingo 2.0 HDI.jpg
    102.5 KB · Views: 1,250
juste like that

It only required 1 diam 10mm to make it work.
 

Attachments

  • tensionning.jpeg
    tensionning.jpeg
    81.4 KB · Views: 1,247
BenBenBen said:
Did you have bad feedback concerning that kind of Belt drive first step?

Usually for this application HTD 8M belts work just fine and are easy to find. Take a look to CONTITECH catalogue.
They have several extremely strong heavy duty type.
 
Back
Top