CVT test run

[thebuggyman1]

Tuning the CVT clutches seems to be more of an art form than science.
When I built the Bigfoot http://www.6x6world.com/forums/max-a...-tall-tub.html I ordered clutches from Recreatives, hoping to get a matched set and not need to tune. I also mounted the 40 horse Kohler on the original motor plate with rubber mounts. I knew there was a lot of movement in the mounts, so I added a couple extra stabilizing springs to help out. The problem I had was the clutch upshift seemed to happen too fast. When I would start out Everything seemed to engage properly, but the machine would take a giant leap forward in speed making trail riding tough...it really wanted to run over the person in front of me.Over the Christmas break I pulled the motor and replaced the rubber mounts with solid ones. That change really improved how the clutches worked.Now I feel I just need a slight amount of fine tuning. My thought is the engagement is a touch too high...like 1900-2000 rpms, but the normal driving range is correct at 2500-3500 rpms.I'm looking for opinions here, so please let me know what you think.

[micmac]

Jim,

What kind of solid mounts did you use? How much increase in vibration did you notice if any?

[thebuggyman1]

The original rubber mounts were 1" tall. so I replaced them with a piece of 1" square tube layed on top of the frame rail. 3/8" holes drilled through it (them, X2) and nuts welded to the underside of the frame. I adjust the motor by sliding it on the motor mount plate, not by the original slots in the motor plate.
Vibration is not an issue...if it were out of balance that bad, it would shake itself apart at high rpms.

[Noel Woods]

I noticed there was no engine shudder, I believe there is a calibration issue between the two clutch assemblies. Otherwise engagement wouldn't come at such high rpm.

[Bazooo guy]

Did you have it on blocks for the video or were you driving on level ground.
I dont think the clutches react the same if the wheels are spinning free.
My understanding is the secondary spring determines the shift point and the primary
determines the engagement point based on rpm.

[thebuggyman1]

I was driving around the yard. It's mostly flat ground, but at about 4 1/2 minutes in I stopped at the base of a small hill (dirt pile). That is where I was able to get a realistic engagement RPM. On flat ground it rolls too easy...like with a good breeze. I tried to keep the machine at normal driving speeds. One thing I did fail to mention is belt tension.
I have 1" to 1 1/8" of deflection, perhaps I should loosen it a little.
What little info I could find on the powerbloc clutches ...... the spring in the primary determines the engagement RPM, the weights determine the upshift. The secondary is more downshift. Of course there is interaction between all three.

[Bazooo guy]

Did you set the correct offset for the clutches?
In the video the belt seems to be on an angle in high gear.
Or is it just the angle of the camera?
This video shows how easy it is to tune the primary.
http://m.youtube.com/#/watch?v=sIYXG...%3DsIYXGRaEb_Y

[Tomo]

hi,
I will refer how to tune a comet 780 drive /driven although i do think the cvtech clutches tune differently because there design is different ..

First are u using the centre to centre distance [eng to trans] supplied by recreatives .This determines the belt length. This influences engaugement rpm.

Assuming the belt is for these clutches eg wrong belt width and the side angle ""v"" of the belt sides gives improper drive and enguagement etc

Has the gear ratios been changed eg more so for high speed ????
Or are they stock
There may be no difference between the bigfoot and the standard gears installed ..
The bigfoot has bigger tyres
The bigfoot will there fore have higher speed gearing.

The clutches need to be setup so it places a very small load on engine engine rpm increases at a moderate speed and not to max rpm straight away as soon as the throttle is touched

The fact of having a 40hp motor will pull thru taller gear ratios very easy and this includes the clutches set up for lesser hp

1 maxium speed faster or slower change sprockets as needed
2 change clutches to influence changing
in a 780 driven u would first change the "ramp angle " the flatter the angle the more acceleration is slowed or resisted ,then u fine tune with springs

This happened in my ssfox previous owner had a black spring 41 degree clutch very fast acceleration . This set up had no pulling power in the low end range as the clutch changed into "4th gear"" very very quickly

hope this helps , clutch set up is very much to each style of machine and to confuse u the application .

tomo

[thebuggyman1]

Bazooo guy: Clutch offset is correct, camera was mounted on the rollbar brace at a complex angle. I have the powerbloc 80 clutch, and it's different than the one in your posted video. I have fixed weights @ 275 g each, I wish I had the adjustable puck ones, that would be too easy to try different weights.

Tomo: There is nothing even close to original with the belt/clutches/motor. It originally came with a Briggs 16hp comet clutches and 45" belt. Both clutches were changed along with the engine, and it now has a 49" belt. Most CVT setups recommend 1 1/4" belt deflection, so I should try a little more than I have now.
Gear ratios are stock MaxII, but it does have the larger heavier tires....everything I've read says to ignore the tire diameter, it's the weight (rotating mass) of the larger tires that matters. Either way, there is no formula for the changes.
You may be on the right track with gear ratio changes though. It would be easy to try some different gears on the jackshafts and see what happens. I have plenty of speed,but better low end creep would be nice.

[Bazooo guy]

I would set the deflection at 1 1/2" and see how much of a difference it makes.
If the belt is too short it will try to creep at low rpm and shift too soon.