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Unread 03-28-2017, 02:08 AM   #11
Not Yet Wild
 
Join Date: Jun 2013
Posts: 14
Default Re: G16 low end power, limit top speed

Hello folk's, I am dragging out an old post to show the objective I am tring to achieve and the great advise I have been given by the more experienced cart wrencher's so far.

My objective to is limit the speed of the cart to run as slow as possible. It will only ever be used to crawl up a steep rocky path to a cottage and then back down. Having the belt engaged between the clutches provides good engine braking going down hill and stops the cart from running away at high speeds by coasting (when the clutches are disengaged). At this point to keep the clutches engaged going downhill we hold the brake and throttle at the same time to engage the driven clutch. Of course this doesn't work well as the secondary will start to open and the cart will pick up more speed than desired. I'm thinking if the secondary won't open, a bit of throttle is all that will be needed to keep the clutches engaged and better limit the speed.

So far I have added a heavier secondary spring and clutch kit to provide more resistance to the opening of the driven clutch. It has helped, but given the clutch opens at all causes the cart to have reduced power and higher speeds than we desire.

The cost of gearing the cart down is big bucks and beyond the budget.

My latest idea (maybe a crazy one), is to mechanically prevent the driven clutch from opening at all by locking the sheaves together with a dyi bracket drilled and tapped into the center hubs of the clutch.

Here is my question. If I am able to make up a bracket that locks the hub/sheaves from opening at all, will the forces of the drive clutch closing on the belt cause other issues?
Will the forces break the driven clutch, or any fab'd brackets made up to lock it closed?

I know the cart will rev to the governor limit setting and this is a good thing providing the the rest of the drive can handle the stress of the driven trying to open against the locked secondary.

I have a few G16's that will have this same requirement so I'm wiling to make an investment in parts/machining costs for this experiment as required.

Hope this explanation make sense so I can get some experienced opinions on the feasibility of the concept.

Appreciate any opinions on how to achieve this.
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Unread 03-28-2017, 09:48 PM   #12
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Join Date: Jun 2009
Location: West MI
Posts: 14,558
Default Re: G16 low end power, limit top speed

Seems like all you would need to do is put a spacer inside the spring to limit what the secondary can shift to. You could also try to wind a stock spring with a lot of preload, that will do what you want to a point, it will keep rpm high at low throttle so it has more braking. Try double the stock preload of 120 degrees go two ramps, adjust the spring holes so you can get it. Or try a umax spring that way its more HD, and they don't cost much. It is much more difficult to get on that way but doable with a stock spring. The springs may break faster I don't know. When you preolad you count the degrees you wind the spring to keep track of what you are doing. The holes are used to change the wind you get when you get on a ramp, you have to be on a ramp to install so the holes serve to give you adjustment between a whole ramp of 120 degrees wind (or preload as they call it, but you will be grumbling when you wind the spring up to get it on lol).

A cut secondary sheave may help a little more it gives a lower low gear to start from and you can cut your sheave or buy one. It just makes the sheaves go together closer so the belt comes out the top a little, so diameter is effectively larger. You can do similar with a wider belt like a 1.25 wide, but it may work or it may drag in the primary if its too much, it depends on how far motor is from the trans.

I have never tried to do what you are doing, but I have run drills with a CVT on them they had a lever that dictated primary size and they ran that exact rpm/ratio until you changed it, so yes it can be done.

The spring in the secondary serves to keep belt tension so it does not slip, the ramps give more belt pressure when you gas it as well as make it downshift, a larger spring gives more static tension but many (except the umax) do not have tangs so you can preload them. The preload when high will make it rev like you have it on the floor even when you are not gassing hard on it, that is one thing you want. The preload basically preloads your torque sensing, it makes it think you are going to gas on it even if you are not the more you preload. Low preload it shifts and rpm drop soon as you ease back on the gas. Higher preload it revs quicker when you gas it and revs little higher at low throttle. High preload it revs all the time like you have it WOT, it will not lower rpm when you ease back on the gas.

I would experiment with lots of preload and try a umax too and see what you get. Try a cut sheave and/or a wider belt like a 1.25. Cut sheave is great for very low speed power like towing and steep hills, it gives you a lower gear. You could also try a shorter belt but if you cut the sheave it will pull it tighter and a wider belt will also do it even more and then the cart wants to move when idling and drag on the starter if you go too far...so make sure you do all that other stuff before you go shorter as you may not be able to. You might consider upgrading the brakes also. You will have to experiment to find out the combo of changes that work like you want. CVT are like that each vehicle needs a certain balance to get what you want, but you find out and you can duplicate it on other similar carts easily you only need to tune it once. You will have to try different settings and springs and belts to see what works and it will take some time.

I have a cut sheave from CPP on my G9, I was running a HD kevlar belt from them too it was great but my new primary clutch does not like it, its too wide. The kevlar belt is a little wider than stock one. I also ran a umax spring and it worked great on trails that way. Again my new primary is far different and it does not like the umax I had to go back to stock spring. But I am not trying to do what you are doing, I can only tell you these things do work on the stock CVT. I can get full shift rpm at about 5mph with the cut sheave and wide belt.
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Unread 03-29-2017, 09:36 AM   #13
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Join Date: Jun 2013
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Default Re: G16 low end power, limit top speed

Thanks again Sho305 for passing along your vast experience.

Last season I installed a heavier spring a (without tangs) and the sliding sheave. It did make a difference, but not to the level I am trying to achieve.

I wish I kept the old spring to try winding it up as you suggest.

I am about to pull the cart out and try shimming the spring. Ironically I won't need to worry about the spring binding up at higher speeds because this cart will never be going any more than a slow walking speed where it is going to be used.

Appreciate your help.
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