Hill Climbing Performance

[stepthrutuner]

The thing about the stiffer contra spring is countering the added forces of hill climbing that want to pull the belt into the rear pulley. The stiffer spring wants to keep the sheaves together for more 'dirt bike' type gear reduction. Lighter rollers will not accomplish this.

[Fox]

Apr 9, 2010 11:39:51 GMT -5 stepthrutuner said:

The thing about the stiffer contra spring is countering the added forces of hill climbing that want to pull the belt into the rear pulley. The stiffer spring wants to keep the sheaves together for more 'dirt bike' type gear reduction. Lighter rollers will not accomplish this.

I have to disagree with you there stepthru. It's the force of the weights that closes the variator and that makes the belt ride up the front pulley forcing the rear pulley to open. Lighter weights apply less force on the variator so it acts the same as installing a stiffer spring.

I don't think grade has anything to do with it. I think it's all about making the most of the small amount of torque by allowing the engine to rev higher before the onset of high gear.

The reason I know this is because I live at the top of a fairly steep half-mile hill and with standard weights I was doing 16 mph. With the the 4 gram weights I was doing about 25 mph up the hill. I never changed the spring.

maps.google.com/maps?hl=en&ie=UTF8&ll=34.201922,-118.158345&spn=0,0.001725&z=19&layer=c&cbll=34.20193,-118.15824&panoid=pocxfgCofVBNwSP4BEbcGA&cbp=12,85.44,,1,-3.54

Stiffer springs are great if you have a lot of torque like drag scooters that have been modified but for a stock 50cc 4t or even a 70cc 4t lighter weights alone will work wonders.

[stepthrutuner]

That's okay. I'm just going by what I've been reading on scooter forums for seven years.

[jetfixer]

Looks like we have opinions for springs or weights. Let's take a poll.

[Fox]

A poll is simply a bunch of opinions.

I simply disagreed that climbing a hill forces the belt into the rear pulley more causing the scooter to slow. I think climbing a hill simply makes the engine work harder.

I agreed that stiffer springs are a great thing for hopped-up race bikes with ported BBK's and over-sized carbs that revv over 10,000 rpm's and have 2 or 3 times the torque. Then the springs are something to consider but on a puny 139QMB with a 70cc kit all you need to do is change weights to achieve better performance.

Try it yourself! Take out every other stock weight and try that hill. You'll be amazed at the difference.

[jetfixer]

Apr 9, 2010 17:03:14 GMT -5 Fox said:

Try it yourself! Take out every other stock weight and try that hill. You'll be amazed at the difference.

That's the plan.

Without an impact wrench or one of those nifty little tools, is there a viable alternative to getting the pulley apart. I don't want to take a chance and break a tooth off the thing.

[90GTVert]

I think either lighter rollers or a stiffer spring would help to be honest. To be more technical though, I believe stepthrutuner's statement is more accurate. I'm no expert on this stuff, but this is how I think of it. Maybe it's all wrong, maybe it makes sense to you, who knows?

Let's say you are traveling along at 50MPH (just random numbers here, not looking to debate top speed of ceratin scoots). Your belt is at it's highest or outermost point in the variator and it's lowest or innermost point in the rear pulley to obtain the lowest (numerical) gear ratio. When you reach an incline or hit a headwind or do anything that puts a big load on the engine with a standard CVT setup the RPMs will drop steadily and in paralell with speed until you reach a speed that the engine can sustain. The fact that engine RPM and speed drop in parallel to each other is indicating that your CVT is still in the same gear ratio.

Now let's say you are traveling at 50MPH with your belt riding high in the front and low in the back again. This time your transmission is setup with lighter than stock rollers and the stock contra spring. Your engine will be operating at a higher RPM, because more revs are necessary to create enough centrifugal force to push the roller weights outward and to their highest points. You hit an incline or a headwind and the scooter doesn't slow as much as it did before the lighter roller weights, but engine RPM and speed are still dropping in parallel. This once again indicates that the gear ratio is not changing. The lighter roller weights have just kept the engine closer to it's peak power than the stock roller weights.

One more time, we're cruising at 50MPH in high gear. This time around you've got stock roller weights and a stiffer contra spring. You hit a hill or a headwind and the scooter begins to slow. It's different this time though. Instead of the engine's RPM and MPH dropping in parallel, the engine's RPM is staying more constant. Force being applied via the stiffer contra spring is forcing the CVT into a lower (numerically higher) gear ratio. rather than simply staying closer to the power band, the correct contra spring can keep the engine right in the corect power band for maximum pull.

That's been my experience with how rollers vs contra springs work. This is coming from a person that will literally spend full days swapping springs and weights back and forth until I approve of the results. I have no mountains to climb, but I do have inclines and declines in my daily travels.

[Fox]

Not really any other way. I've seen this video here but I couldn't get it to work for me. It kept slipping.



Just get a 12 volt impact. They work good. They kind of wind up then wham! It takes a few hits to get the nut loose usually. I hit the nut four or five times when tightening it.

Here's a vid of a British guy using one. He says:"To show you just how easy it is to take a variator nut off with one of these. Just buy one! They're only 20 quid."

[jetfixer]

I don't know what the max RPM of my little motor is. Let's say for the sake of argument that I can't get any more RPM from it. In that case the lighter weights wouldn't help any because I can't make my motor spin any faster to force the variator into the higher gear. In that case a stiffer spring would be a better option. Will the engine just naturally run at a higher RPM with smaller weights?

I guess I'm getting lost in the visualization here. If the motor starts bogging down because of headwinds, hills, etc... don't you want to keep heavier weights to keep the belt on the high side of the variator? More turns on the back end for each turn on the front. Or am I just dense?

I'm not questioning your results or your experience with this. Just trying to get it straight in my head.

[Fox]

yes the lighter weights will make it rev higher all the time. From 0-40MPH it'll rev higher than it does now. You'll lose some MPG but you'll go up hills and get to speed faster. The top speed doesn't increase but you get there quicker with the 4.5 gram weights.

That engine of yours will run at about 8000 RPM Max and most of it's torque is created at the higher rpm range. The lighter weights will in effect increase your existing spring's tension because they will exert less force on the variator back plate at the 4-6000 rpm range delaying the closing of the front pulley halves causing the engine to rev higher all the time which = more torque at slower speeds.

Look at it like a bicycle with gears in the back. If you take off when the chain is on the largest rear sprocket it's easy to pedal and then as you accelerate you move the chain to a progressively smaller sprocket in the back making it progressively harder to pedal. At the same time you did that you moved the chain to a progressively larger front sprocket making it even harder to pedal. Your legs are only so strong so when you take off on a hill you stay in a lower gear until you reach the top of the hill. The lighter weights accomplish that. They delay the up-shift into running gear until the engine revs out and on a hill that's a good thing.

[drawkward]

Apr 9, 2010 18:34:54 GMT -5 jetfixer said:

I guess I'm getting lost in the visualization here. If the motor starts bogging down because of headwinds, hills, etc... don't you want to keep heavier weights to keep the belt on the high side of the variator? More turns on the back end for each turn on the front. Or am I just dense?

Imagine it like this. Say you are cruising down a hill on a ten speed bike in the highest gear (10) so you can obtain the fastest speed, and not have to pedal SUPER fast. Now when you get to the bottom of that hill, you start going up the next hill. Do you want to shift down, or try to pedal up in 10th gear? Thats sort of what you were suggesting just now, I think.

The way I picture it is like this. Heavier weights make it shift up faster (prematurely if too heavy). Light weights make it shift up slower (keeping you in a low gear if too light).

If you have ever driven a manual transmission in a car or motorcycle - compare it to starting off in 3rd gear as opposed to 1st, or down shifting to go up a really steep hill. Heavy rollers won't let you down shift to where you need to be.

I could be way off, I'm still a noob to this stuff. But it makes sense to me.

---

Edit: Damnit, JM! you beat me to it. lol

[stepthrutuner]

Well you can't disagree with this. A tighter rear spring will result in less belt slippage.

[drawkward]

I purchased roller weights before anything else, cause my hill climbing abilities were lacking. They helped for sure. The spring also helped when I got it in finally... But I still have trouble climbing hills, so what do I know? Useless post.

Oh and I'm not voting, cause there is no "both" option.

[stepthrutuner]

And here's another one I think you will have trouble contending:

Provided your torque-driver spool is functioning freely and properly a stiffer contra will 'downshift' the belt quicker than lighter rollers will.

[jetfixer]

Just ordered a set of 4 and 5 gram weights. Figure I can try three different weight ranges with them to see what works best. Got them for $10 a set so I figure they probably aren't the best, but I can get a good idea of what will work then order some sliders.