CVT Dax 10T Doesn't Fit, But...

Ouch. Didn't the ease of filing it initially give you a clue?

Buy another one, file it to fit, heat it cherry red with a blowtorch and quench in used engine oil. Easy. Thats if its steel...
True. But, after the heat treatment, it will be brittle. To relieve the stress inside the sprocket, and make it less brittle, after the heat treatment, pop it in the oven and bake it at 450 deg F for about two hours, then take it out, and let it cool to room temperature, gradually. Afterwards, it'll still be hard, but, it'll be less likely to break under stress.

Shrapnel: The left-hand thread freewheel that staton (and others) sell IS the standard 1-3/8 - 24 TPI. Just in left hand threads.
 
Last edited:
Tach Update

I finally got around to installing the Northern Tool Tach on my heap. It seems to work fine albeit the really small readout for these aging eyes. It's quite tiny. It is similar in function as the speedometers where the wheel goes around a few turns before the speed change registers. There is a small lag between the throttle movement and the readout. This is normal though in digital meters and quite liveable.
It shows the Robin engine popping up to the mid 5000RPM range on throttle up. It shows me cruising in the 5500 to 5700 RPM range. Yet my speed is around 25MPH. Using the handy dandy gear calculator with my CVT, 12T to 44T and 26" wheel, the CVT is only using about a 4.5 primary ratio. Nowhere near the 2 or 3 range it's supposedly capable of. That is somewhat disappointing. Unless the ratio calculator is off. OR the tach. is off. OR I and my tank just flat out weigh too much.
I'll be trying the 56T final sprocket when time permits to see if there is an improvement. Maybe its time to play with different variator weights.
I need a chase person to follow me and view the CVT in action with the cover off. Alas, I'm alone here.
Later.
WC
 
hmmm, wonder why it's not pulling all the way up to 'high"

if you had a 30T on there, even with it only pulling 4.5 from the cvt you would be doing 37mph.

i have heard of the secondary reduction being such that it wouldn't allow the cvt to get enough rpms to pull on up, maybe it was in Large Phillipino's Buggy Bike gets a cvt thread.

i'll try to find it.

steve

ps, yep that's the thread, from post #10 on, very good stuff !!
 
Last edited:
I finally got around to installing the Northern Tool Tach on my heap. It seems to work fine albeit the really small readout for these aging eyes. It's quite tiny. It is similar in function as the speedometers where the wheel goes around a few turns before the speed change registers. There is a small lag between the throttle movement and the readout. This is normal though in digital meters and quite liveable.
It shows the Robin engine popping up to the mid 5000RPM range on throttle up. It shows me cruising in the 5500 to 5700 RPM range. Yet my speed is around 25MPH. Using the handy dandy gear calculator with my CVT, 12T to 44T and 26" wheel, the CVT is only using about a 4.5 primary ratio. Nowhere near the 2 or 3 range it's supposedly capable of. That is somewhat disappointing. Unless the ratio calculator is off. OR the tach. is off. OR I and my tank just flat out weigh too much.
I'll be trying the 56T final sprocket when time permits to see if there is an improvement. Maybe its time to play with different variator weights.
I need a chase person to follow me and view the CVT in action with the cover off. Alas, I'm alone here.
Later.
WC

If you're not shifting right, that's all about CVT tuning.
Welcome to tuning experimenting he11.
This is what I was speaking about.

It helps to make a log and write down what changes with each thing you do.

I would try much lower gearing first.
(at least 56tooth, but more like in the 70s....)
The gearing has to be right on to have these CVTs shift right.

Then try heavier rollers.
If it's not shifting all the way to the top of the ratio,
that's because either the gearing is too tall and the motor can't pull it,
or the rollers are too light.
Heavier rollers help it shift into the higher gears earlier and easier.
 
44t driven sprocket
12t drive sprocket
apx. 3:1 in the gearbox

total ratio is 11:1. The overall gear ratio is too low - this is why the CVT won't ever get out of the mid range. (it's a 50 MPH top end)

If you have a 56t rear sprocket, the overall ratio jumps to 14:1. This is probably still too low (38 MPH top end.)

at 18:1 (30 MPH top end,) it should work. This means that you need about 6:1 reduction on the sprockets, so, with a 12t drive sprocket, you would need a 72t driven sprocket.
 
Last edited:
i'm thinking more like 80T and 20:1.

the main problem here is limited rpm range. if you want to cruise in the 5500-5700rpm range by the time you get the gearing to support the cvt you aren't going to go over 25mph anyhow.

these cvt's were designed to give small high rpm engines a resonable take off after they were geared for the best topend they could give.

steve
 
Yeah. My approach has been to
  1. Calculate the high end speed/gearing first, knowing that approximately 10-15% of the available power may be lost in the CVT. (In other words, knowing that you won't be able to achieve the same max top end that you could without the CVT)
  2. Then, back off to the 5500 RPM range, to determine the cruising speed, when the CVT pulleys get to a 1:1 state.
  3. Finally, calculate the max torque situation (at 5500 PM,) as if you're climbing a steep hill. (You divide the 'cruise' speed, from step 2, by the pulley ratio of 2.2)

With this approach, if you wanted to hit 30 as a top end, then you wound need 18:1 total reduction, cruise would be at 23.6+ MPH, and max torque at 10.7 mph.

Now, if there are lots of hills, and your main objective would be to have hill climbing ability, then you could work 'backwards.' Suppose that you needed to have max torque at 9 MPH. because of steep hills. Multiply by 2.2 to get the minimum 'cruise' speed of 19.8 at 5500 RPM. The gear ratio could be calculated to be 21.5, meaning that you would need an additional 6.7 gear reduction after the gearbox on the CVT. and, with a 12T sprocket, you would need a 81T hub sprocket, or, a jack-shaft. The top end would then be about 25 MPH.

I think the key thing to remember is that the CVT isn't the cure-all. Yes, it can increase acceleration (and hill climbing torque,) but it can't do this AND maintain the same top end that you could without a CVT. There are some losses in the CVT (on average, over the life of the CVT belt, about 10%) that will reduce the top end that can be achieved.

And, I think that you need to get the system gearing right, before you start playing with the variator weights.

Possibly, the chart below will help in understanding what the CVT does for you, when the bike is geared for climbing, per above.

Assuming that you peddle up to 5 MPH, then gun the engine. Assuming the clutch pulls in at 2000 RPM, engine RPMs will quickly rise to the 5500 RPM level, and will then level off until the bike's speed reaches the minimum 'cruise' speed breakpoint, and then, since the CVT has no further pulley ratio changes to make, the engine RPM then starts rising as the speed increases.

Adjusting the pulley weights has the effect of lowering or raising the 'flat' portion of this rpm-speed curve. Adjusting the system gear ratio has the effect of shifting the curve to the right or left (shifting the the first two 'breakpoints and the top speed to the right or left.)
 

Attachments

  • Chart - RPM vs Speed CVT.JPG
    Chart - RPM vs Speed CVT.JPG
    20.6 KB · Views: 264
Last edited:
The other thing to keep in mind is the legalities of the situation. In AZ, with the 20MPH MB limit, it may be beneficial to have the cruise 'break point' at about 20 MPH. Then, when your motor starts to increase RPMs, you know you'll need to back off the gas a bit to stay ... legal.
 
Legalities be ****ED!

At least for me.
AND...its a Subaru EHO35...ALWAYS keep this in mind when I post MY findings.
I was somewhat surprised and at the same time humbled that my posts are not falling on deaf ears. I'm glad there is still some interest in these CVTs.

So, regarding the Subaru EHO35... the MAX HP of a whopping 1.6hp is achieved at 7000 RPM. Max Torque is achieved at about 46-4800 RPM.
There is NO WAY IN HE11 that poor little B****RD is gonna hit 7k with (200lb)me and a 100lb bike. The chart is showing No-Load figures.
Likewise, if I'm jumping from 2k to 5k on throttle up, I'm IN the power band for this engine.
In reference to my gearing, Yeah, I think it should get lower. Although, if I've got to go to a 70 or so tooth rear driven...well, I think you could see that it would be a HUGE sprocket. That having been said, I've been looking at ways to use a belt system with this critter. Whereby it would have a small 1-2" driver coming off the final to a Whizzer or GEBE type driven pully. Which would be about as big as a 70-80 or larger chain sprocket! AND, I HATE CHAIN DRIVE!
I really do.
Then, even IF a 10T or 12T to 70-80T got the engine to rev higher, in order to reach the magic 7000 RPM, this CVT wouldn't get me any more speed than I could pedal on a really BAD day! Nor, do I ask it to.
What I keep in the back of my mind is that it gives me gearing options I never had before with the friction drive AND the engine is in its BEST operation zone. Meaning it (the engine) should last longer than one that is driven at WOT just to satisfy some performance criteria.
I'm not blasting anyone here for their input and concern. I'm just trying to remind some that the EHO35 is NEVER going to perform like the Tanaka or similar 2 strokes that can hit 10-12k or more RPM, CVT or not.

NOW! All of that having been said, I have tried preliminary 'tuning' of the CVT by removing 3 of the weights. FAIL! Don't bother if you are using a 4 stroke of limited HP. Results are: it pulls fine off the line but that's all folks! No top end at all. My next tuning trial would be to go with HEAVIER weights as CBR suggested. If I can get the RPMs up, even slightly say to 6k, it seems the heavier weights would throw out faster to pull the variator in and get closer to the Holy Grail figure these CVTs can produce. All the while keeping in mind this is a EHO35. JEEZE! I wish someone would try this with a high HP 2 stroke. AND on a bike, not a GoPed. I'm limited in my research materiel without a grant of some sort. (hint) LOL
Lighten UP!!! This is supposed to be FUN!
Anyway, I'm STILL enjoying my ride. Just playing and reporting. AND, on the side, going CRAZY with all my lighting stuff that I'll soon be posting in the appropriate forum.
All BS aside...I'm glad I put the RPoMeter on my bike (as well as the CVT) as it gives me some really valuable input that I was only guessing at before.
Thanks for watching...
WC
 
If you're not shifting right, that's all about CVT tuning.
Welcome to tuning experimenting he11.
This is what I was speaking about.

It helps to make a log and write down what changes with each thing you do.

Yeah, I got a log...
...it's called a credit card statement!
HAHA
Thanks for the input CBR. Stop being such a stranger. AND... What are you working on of late???
WC
 
Back
Top