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Re: Yamaha YZ250F

Posted: Sep 16 2022 5:39am
by E-Max
TysonScott wrote:
Sep 15 2022 5:26pm
https://www.facebook.com/groups/electri ... 911125831/
this person used a qs 180 90h with ND961800 pushing around 100kw! that would be pretty insane on a shifter kart
[/quote]

wow this insane! :shock:
I am not sure if the ND961800 is needed, maybe the ND961200 is enough :?:

Re: Yamaha YZ250F

Posted: Sep 16 2022 6:32pm
by dougf
j bjork wrote:
Sep 16 2022 4:07am
Doug, how do you limit the charge then? (I think you were running 24s?) Do you guard it and turn it off when it is done, or let the bms cut if necessary?
I dont think I will buy one, but I am curious anyway :wink:

I havent really tested the new gearing yet, it will probably be this weekend.

Tyson, I have seen that one before :)
Very cool bike, but is it possible with that short wheelbase and skinny tire?
I dont know what to make of it, if it has the track version the controller should be capable of 100kw.
When I was messing with the sevcon it seemed like the motor was limited because of its higher inductance compared to a z-force 75-7 for example.

It is also interesting that he seems to have the earlier, 28Ah version of passat gte cell modules. Where I have the newer 37Ah version, that in my limited test had lower ir than the earlier ones :)

A 10.2x and 210km/h run in sneakers, jeans and a sweatshirt :?
It has its own battery charger inside. When I ordered I got it made for constant current up to 100.8v, then constant voltage. When the current drops below some threshold the engine shuts off. And yeah BMS takes care of balance, although the molicels are pretty much always bang on.

So that guy is making 100kW with a 180 and a 961800? Needless to say Im skeptical. Assuming NO sag you would need to run 125V which is higher then the max voltage in of a 961800. Thats before losses due to efficency, chain cabling etc. Id say this motor starts dropping off pretty quickly after about 500 battery amps which means around 40kW before losses.

Doug

Re: Yamaha YZ250F

Posted: Sep 16 2022 7:28pm
by liveforphysics
That drag bike looks legit to me. 125mph trap speed and 10.4 1/4mile takes real horsepower to do, that's faster than my 180hp GSXR-1000's fastest ET.

Re: Yamaha YZ250F

Posted: Sep 17 2022 8:56am
by j bjork
If it is the track version of the ND981800 it should be capable of 1350 batteryA.
It looks like he is running 2 (12s) battery modules, so that should be 24s.
Charged to 4,2v/cell it would be 100,8v.

If he is able to pull 1350A, how much would it sag, to 80v?
80x1350=108k

I think my tests on cells like that gave about 1,5mOhm resistance/cell.
That would mean 36mOhm in 24cells, and 48,6v drop at 1350A.
But that was on used cells in room temp. His might be new (I saw a post about modules from flooded new cars) and they might be heated before a run.

Even if that is possible it dosent mean 100kW output, but maybe 100kW from the battery.
I think sevcon predicted about 45kW (from the motor?) at 108v.
But if the run at the strip is real it would for sure take power..

Re: Yamaha YZ250F

Posted: Sep 18 2022 12:03pm
by liveforphysics
I would be shocked if he wasn't pre-heating his pack before the drag race. It helps too much not to do it.

Somehow he really ran a blazing ET and trap speed, and not possible to do that without making a LOT of mechanical shaft power.

Re: Yamaha YZ250F

Posted: Sep 19 2022 11:59am
by j bjork
It is amazing with such simple stuff that you can just get at a reasonable price.
Nothing fancy custom made in the drive line from what it seems :o

Back to my bike:
I was out riding quite a lot yesterday, on a tricky track with a lot of rocks and roots.
But it had some faster parts too.
I am surprised again how much difference the gearing makes :o

I thought on this bike with so much power it wouldn't be that noticeable, but it changed character a lot.
It lost the bite, the aggression. It still has power, it just doesn't respond at all the same.
( I went from 7,1:1 to 6,3:1, a little under 13% higher or faster or what to call it)
I got more used to it after a while, and I think I will ride it like this for now.
But I think lower gearing and maybe lower phase amps would be more efficient, and probably more responsive on the throttle.

Re: Yamaha YZ250F

Posted: Sep 19 2022 8:38pm
by Dui, ni shuo de dui
j bjork wrote:
Sep 19 2022 11:59am
It is amazing with such simple stuff that you can just get at a reasonable price.
Nothing fancy custom made in the drive line from what it seems :o

Back to my bike:
I was out riding quite a lot yesterday, on a tricky track with a lot of rocks and roots.
But it had some faster parts too.
I am surprised again how much difference the gearing makes :o

I thought on this bike with so much power it wouldn't be that noticeable, but it changed character a lot.
It lost the bite, the aggression. It still has power, it just doesn't respond at all the same.
( I went from 7,1:1 to 6,3:1, a little under 13% higher or faster or what to call it)
I got more used to it after a while, and I think I will ride it like this for now.
But I think lower gearing and maybe lower phase amps would be more efficient, and probably more responsive on the throttle.
Get crazy, make some kind of gear swicthing system so you can get the best of both worlds!
You already have the slight efficiency loss of an intermediary chain transmission stage anyways, so you wouldn't loose anything except maybe adding a little bit of weight.
Sure would be fun to see!

Re: Yamaha YZ250F

Posted: Sep 20 2022 10:51am
by j bjork
The only reason I changed gearing was to be able to use sprockets available to buy "off the shelf".
I dont have any other benefits that I know of yet, so some kind of transmission with gear change dont make much sense to me :wink:
If that is what you meant?
I suppose it will have higher top speed now, but that is not something I use anyway.

The problem was that the sprocket on the motor was too soft, it was made from ordinary steel.
I think I will check with the watercutter if he can just cut up the splines a little if I get sprockets with a smaller spline, so I can get a good 10 or 11 tooth sprocket on the motor.

Re: Yamaha YZ250F

Posted: Sep 21 2022 8:10pm
by dougf
That 100kw motor is probably rewound then because you're not getting 10krpm at 100vdc, or 100kw for that matter. I will try get my bike on my dyno this weekend. I should be able to do consecutive pulls while upping the battery limit. My guess is after 500A either my battery or motor starts leveling off.

The water jet guys should be able to cut you a sprocket from hardened steel. Or at least out of hardenable steel. You can always go up on the rear sprocket. I believe the biggest that will fit without modification is a 54T. The 60T i have on the back is about as big as Id go before being worried about damage from rocks and to fit it you need to lower the chain guide about an inch.

Doug

Re: Yamaha YZ250F

Posted: Sep 22 2022 11:16am
by j bjork
Maybe you can reach 10k rpm with a lot of FW?
I think the qs138 on my ktm pulls to at least 8000rpm, and that is around 80v I think.
With a lot of FW that is.

I will have a talk with the water jet guy, and see if he has some suitable steel.
Last time he cut these when I had specified what steel jt use, but I think it was more like a test.
The idea with using a finished sprocket and cut new splines was to get the right hardness and the right tooth profile.

Image

I was too curious to just leave it, so I opened up to the primary reduction after the ride last weekend.
Looks good, the 18 toot seems to be a winner :)

Ill wait for your updates of the dyno pulls :D
Dont forget to test those rpm/% settings, KI/KP, weak character etc. before you push too much on the amps :wink:

Re: Yamaha YZ250F

Posted: Sep 22 2022 4:24pm
by speedy1984
After setting up my 96/850 version controller i got a rated speed of 7400rpm on my v3 motor.Most people go straight into self learn very first thing when setting up for the first time.I then realised i was doing this in middle drive mode as they come from the factory,and with the percentages again adjusted in the app already you will only get the lower end on the rated speed rpm numbers i also got on middle gear.Switched into drive/high speed and rated speed then into self learn again and its now bang on what it should be.

Re: Yamaha YZ250F

Posted: Sep 22 2022 11:04pm
by Dui, ni shuo de dui
j bjork wrote:
Sep 20 2022 10:51am

If that is what you meant?
Yeah, that's what I meant, making a 2 speed transmission. Wouldn't be too difficult to build from what I can see on your pics, and you'd still have the same efficiency since you already have this intermediary transmission here anyway.
This way you could have a low gearing for super high torque at relatively low speeds (wheelies, burnouts and whatnot) and a higher gear for high speeds cruising at the best possible motor efficiency rpm, avoiding the use of flux weakening which is very power hungry.

The only real technical challenge IMO would be to make the axles a little bit longer to fit another gear and a selector next to the current ones. That wouldn't be necessary on the motor side since it would be possible to machine a spacer and attach it on the first gear, but that would be necessary on the secondary shaft since the selector would have to be able to slide on it.

I would definitely try that if I had the same system you have right now, would be a really fun project and a great technical challenge. Just a thought of course, I don't think you'll do that anyway but I had to propose it since your system is so well suited for this ! :wink:

Re: Yamaha YZ250F

Posted: Sep 24 2022 9:49pm
by amberwolf
Dui, ni shuo de dui wrote:
Sep 22 2022 11:04pm
Yeah, that's what I meant, making a 2 speed transmission.
How about something along the lines of Thud's 2-speed dog-clutch system?

Info in this thread on 2speeds:
viewtopic.php?f=28&t=8644
drawings
viewtopic.php?f=28&t=7832&start=30#p309846
download/file.php?id=72230