Yamaha YZ250F

[j bjork]

From my experience of 45 years with motorbikes, I would say: this is TOO TIGHT.

In any case I would add a chain tensioner of whatever kind (something with a spring or an oil dampener) in this primary chain drive,
since a chain is permanently changing its length, due to wear, and forces transmitted.

And I think, a possibility for moving one of those two axles would be required, for adaption of the chain tension
(as it is usually realized in motorbikes' rear swing arm axle mounts).

It is supposed to be 3mm between the chain and the housing to the rear of the chain, but this is more like 1mm..
I will make some changes and try to get the 3mm that I planned, I hope that will be enough.
Otherwise I guess the chain will make the room it needs :wink:
It should be possible to mill or grind out some material just where the chain are afterwords if needed, and be able to keep at least 3-4mm material for the sealing surfaces.

Do you really think a tensioner will be necessary for this short chain? I am trying to avoid it, to have less things that can brake..
The motor is movable back and forth to adjust tension. The chain will also be in an oil bath, so I dont think it will wear very fast.
It has room to move everywhere else, just not to the backside of that sprocket..

 

[j bjork]

very nice work! You can get 1/2 links for the chain. I think this roller tensioner idea is interesting:
https://www.renold.com/products/accessories/roll-ring/

did you get good news about the motor being built and any progress on the controller/s?

It seems to me that a half link will be a little weaker, so I am trying to get all the gearings to work without it.
But if necessary I can always go that route later.

That kind of tenioner might be something, but I havent seen any in fitting dimensions.

As far as I know they will start building the motors in about 2 weeks.
I can only hope that they do, and that they dont change anything from the drawing I got :?

I really dont know how it will turn out with the controller or controllers.
2 smaller would be nice to fit where the radiators where.
The powervelocity sounds interesting, but it still seems unknown when it will be avalible.
The pre production once delivered so far is limited to 400 phase A and 200 batt A, that is a little on the low side even for 2.

Besc G4 looks interesting, but small for one. Overkill for 2. But I guess a little overkill never hurt anyone :lol:
I have no idea when they are available, and then it is probably to build yourself..

 

[j bjork]

Great work with the wood fibre.

Glad you tried the single primary reduction and liked it, have you been able to maintain the original driven side sprocket position with the 17T sprocket on the reduction side or has it had to shift a little forward.

Also do you have a shaft yet for the reduction? I was going to use Honda sprockets from my bike but they have a weird 17 Tooth spine which I can't find any axle/shaft for off the shelf, would cost about £200 to make a custom one.

I just decided it would be too complicated to build the 3 stage reduction. If I was to use the the yamaha gears I would have a good output shaft, but I would probably have to make another input shaft. And a housing for it. Etc.
I looked at some industrial gears, but they seemed to get very wide if they should be able to handle some torque.

I havent really cared much about the shaft yet, I planned to find out exactly how long etc. it should be first. Then either make it myself, and get someone to cut the splines. Or make all of it.
I plan to use the same splines as the motor. If it will be to expensive to custom make, maybe there are some standard shafts that will work. As it seems to be a widely used spline model in china for example.

 

[Elektrosherpa]

Do you really think a tensioner will be necessary for this short chain? I am trying to avoid it, to have less things that can brake..
The motor is movable back and forth to adjust tension. The chain will also be in an oil bath, so I dont think it will wear very fast.
It has room to move everywhere else, just not to the backside of that sprocket..

I understand the idea of having less parts.

If the chain is running in oil, this will sure make for less wear.
But anyway you will have to check it very often.

Usually even short chains in motorbikes' combustion engines have tensioners.
For example the camshaft chain of my Suzuki GSX400 :
I would guess it is not much longer than your primary chain -
and it much is less stressed out, because it only moves the camshafts, not the whole vehicle.

How big is the distance between the two axles?

 

[LeftieBiker]

Usually even short chains in motorbikes' combustion engines have tensioners.
For example the camshaft chain of my Suzuki GSX400 :

That's because no one wants to have to open up an engine to make frequent cam chain tension adjustments. A drive chain that can be adjusted easily doesn't need a tensioner unless it's long or the distance between the two sprockets changes as the suspension moves.

 

[rivvs]

Looks like it is going tobe a nice build! What final gearing are you looking for? On my build I used a qs 138 90h with the same two stage reduction as you with 10/15 sprocket from the motor and 13/54 to the wheel so i would think since your motor is more powerfull you need less than that!
Little video of my bike
https://www.instagram.com/p/CIZPpj7BruU/?utm_source=ig_web_copy_link

 

[j bjork]

Do you really think a tensioner will be necessary for this short chain? I am trying to avoid it, to have less things that can brake..
The motor is movable back and forth to adjust tension. The chain will also be in an oil bath, so I dont think it will wear very fast.
It has room to move everywhere else, just not to the backside of that sprocket..

I understand the idea of having less parts.

If the chain is running in oil, this will sure make for less wear.
But anyway you will have to check it very often.

Usually even short chains in motorbikes' combustion engines have tensioners.
For example the camshaft chain of my Suzuki GSX400 :
I would guess it is not much longer than your primary chain -
and it much is less stressed out, because it only moves the camshafts, not the whole vehicle.

How big is the distance between the two axles?

I dont think you can compare a timing chain and a drive chain. The timing chain needs to have tension all the time to keep the timing stable. That is not necessary here.
I also worry that if I should use a tensioner it would take a lot more beating than a timing chain tensioner.

The distance is between 135 and 160mm. Im not sure I will be able to run 135mm, it will be very tight between the front sprocket on the secondary chain and motor. But 11/17tooth with a 36link chain will be 139,2mm or something like that, and I think that should work. 160mm will also be difficult to reach, especially if I have to move everything 3mm. I might change the max to 155mm.
I can get many combinations to about 142-145mm, and I think that is the best range to start with. Then I still have some distance to adjust when it wears.

 

[JimVonBaden]

Your chain, with the proper tension, will be fine without a tensioner. There are lots of examples of chains under much more stress that go over 100K miles without a tensioner, and yours will not be that stressed. I think it is a great design, especially if it runs in oil.

 

[j bjork]

Looks like it is going tobe a nice build! What final gearing are you looking for? On my build I used a qs 138 90h with the same two stage reduction as you with 10/15 sprocket from the motor and 13/54 to the wheel so i would think since your motor is more powerfull you need less than that!
Little video of my bike
https://www.instagram.com/p/CIZPpj7BruU/?utm_source=ig_web_copy_link

Thanks, I dont know yet what gearing I will end up with.
I dont have enough data on the motor, and I havent fully decided on voltage or controllers either.
So it is just a guessing game at this point.
But I can get 7:1, and I dont think I have to go lower than that. I think I will end up in the 6:1 range somewhere.
From the info I got it seems like the motor will have a kv of about 55 if I remember correctly.

So you have 6,23:1? That sounds high for that motor. I guess if you feed it enough phase amps it might be ok.
I went from 7:1 to 8:1 on the ktm with 138 70h, that made a lot of difference on the power at low speed. More than I expected.
Have you tried gearing it down more?

 

[rivvs]

Yes 6.23:1. Im usin a bac 8000 at 72v. In the video it was with 600 phase amp. This give me a top speed of 116 km/h. At first I might need to gear it down but after testing it I like it like that. It can lift the front wheel up at any speed even when stopped( like lifting the fron wheel to turn around enduro style) and I dont need to go full throttle.

 

[thoroughbred]

how about a silixon?

https://www.pohlbock.com/produkt/controller-sl-1060/?v=3a52f3c22ed6

 

[j bjork]

how about a silixon?

https://www.pohlbock.com/produkt/controller-sl-1060/?v=3a52f3c22ed6

I have looked at them, I wrote about it on page 2.
There are some questions about performance, and how much access to settings you get.
I think that the specs is not really clear on some things.
But the biggest issue is the low voltage. I want to be able to go 30s

 

[j bjork]

I started over with the models.
Now it is more clear what I want, and how to do it.
So it should be quicker and easier to do it again, or at least that is what I thought

Trying to make sure everything is strait.

I didnt plan to make the holes for bolting it to the frame at first, small differences will mean that it wont fit..
But if it do fit, it will be easier to get a nice end result :wink:

There are some changes made after I made the model, but they are too small to make a real difference.
So I dont think I will make a new one.
It is the bottom mounting holes, you can see small ones in the model.

My drawings are almost understandable now, this is how it will look:

In the bottom of the drawing is the bottom mounting holes that are just the small ones in the model.
Better than my earlier drawings at least:

I'm not sure I even understand this one myself..

Btw. thanks for the comments that I didnt respond to, they are appreciated too :thumb:

 

[MikeSnow]

First of all great work! How important is it that the motor is completely aligned? Does a small angle make a big difference?

My build is starting in a month and I was hoping to weld the mount since I dont have access to a CNC. Guess alignments will be a bit tricky.

 

[Shazzy]

Where did you pick up the golf batteries from? Finding it hard to source them in London

 

[Torti]

why do you all build this deflection and not like the original direct drive?

 

[j bjork]

First of all great work! How important is it that the motor is completely aligned? Does a small angle make a big difference?

My build is starting in a month and I was hoping to weld the mount since I dont have access to a CNC. Guess alignments will be a bit tricky.

I dont really know, but I guess you can get an idea by looking at the chain and sprocket when spinning it with the wheel in the air.
If you can see that the sprocket dosent run strait in the chain it probably is to much..

Where did you pick up the golf batteries from? Finding it hard to source them in London

I guess this post isn't meant for me?
The golf batteries I have in the ktm I found locally here in Sweden :wink:
c70r did write that he found golf batteries in England though.

why do you all build this deflection and not like the original direct drive?

I'm not sure what you mean with " original direct drive", If you mean hub motors it is simply not for off road.
There is a lot to read about it on the forum.

Original on the bike is far from direct drive, it is a reduction form the motor to the transmission.
Then a reduction in the transmission, and finally a third reduction between the transmission and rear wheel.

But I will assume you mean why not a single stage reduction between the motor and rear wheel, like I did on the ktm?

First it is not possible to do with a good result on a big motor like this, because the shaft will end up in a bad position.
The big diameter of the motor would mean the shaft will be too high and far from the swing arm pivot point.
The length of the motor would also mean it will stick out a lot to the right side when it has to be in line with the chain.
You wont be able to keep the brake pedal, and it might even be in the way of the foot.

Secondly you will have to run a small sprocket on the motor and a big sprocket on the wheel to get enough reduction.

 

[j bjork]

How it looks now with the chain:

I hope this is enough room..

The other side with a new plate from an updated drawing.

It is not a lot of extra room for the batteries, they will probably end up at least 10mm higher than this.

I went for an extra bracket, I think it will be very stable without it too.
But just in case, and it should limit the stress on other parts.

 

[Elektrosherpa]

I hope this is enough room..

Looks good to me ! :thumb:

 

[j bjork]

Not much progress lately.
I have been considering getting parts cut out for the motor mounts, but everything seems so uncertain..

I emailed almost two weeks ago to qs for confirmation that things go as planned with the motor, and that there wont be any changes to the design. So far no reply.. I took it easy, thinking they probably has a lot to do after Chinese new year.

lately I have found pictures of the motor that I assume another buyer got from qs, but also a screen shot from another potential buyer where qs tells him they wont be developing the motor, and they only sell a few samples. They wont be selling more samples now.

So I guess I have ordered one of the samples they will make, maybe?
Or didn't the representative I have been in contact with know that there will be no motor, and now ignores me?

Or have they changed their mind since they told the other guy that there will be no motor, and are making it?

So many questions and so little answers :?

 

[dforesi]

Sounds frustrating. Good luck!

Keep us updated!

 

[j bjork]

I sent a new mail and got a quick reply this time.
There he says that it is in production now.

I sent a mail again and asked if it is just a few samples, or if they will start mass production?

I got a reply saying "we can go mass production for the motor"

So I am still not sure what it means, but I guess they are making a few pre ordered samples for now.
Then maybe start mass production?
It seems a bit strange, they must have invested quite some time and money in this motor.
I wonder if there might be something wrong with it, that makes them hesitate :?

 

[hugok]

Who is your contact? I have got some good response from damon@tzquanshun.com.

 

[j bjork]

Harry Zhou. He has normally been fast to respond, and I at least was able to order a motor :wink:
It seems some others havent. Now I just have to hope I get it..
I dont always get an answer to all questions, and sometimes not the answer I am looking for.
But I dont think it is a good idea to start contacting other people at this stage, but maybe next time I try him.

 

[Routybouty]

Great project! I kinda forgot that wasn't a real motor and was confused why you ordered a new one. :lol: :lol: