Centrifugal Clutch vs Torque Converter

Do you prefer a centrifugal clutch or torque converter


  • Total voters
    16
#1
Ok so I wanted to make a thread on the benefits of each drive system and the disadvantages of both to help anyone in need of some information on this topic.

Centrifugal clutches have springs wrapped around the clutch shoes. When the engine rpm is raised the centrifugal force makes thes waits fly outward. At a certain rpm the clutch shoes contact the clutch drum and start to move your machine. As they engage, they slip and make heat which is bad for Clutches and cvt. Now as the rpms raise the clutch shoes will fully "lock up" against the drum and the clutch will turn as one piece, stopping heat build up and allowing it to cool. When the rpms drop the clutch shoes will retract from the drum and now you will essentially be in a neutral position. Raise rpms and the clucth will engage

Torque converters have 2 pulleys will movable sheaves that allow for continuous and infinite gear ratio changes between 2 set high and low rations. The driver clutches is similar to the centrifugal clutch in the way that there is springs and clutch shoes " a weight set" and it operates with centrifugal force. The driver pulley has a stationary side of the pulley and one side that will move in and out. When the clutch engages it will force the pulley to larger diameter. The driven pulley is spring loaded and will contract in relation to the driver pulley. The driver pulley as it engages will have smaller diameter and the driven will have a larger diameter. Providing gear reduction and more torque with less speed through the chain and to the wheels. As rpms increase the driver sheave will force the pulley and belt to a larger diameter and the driven pulley will be forced to a smaller diameter. This will be the "high gear". The cvt starts out with a low ratio and works to a higher overdriven ration. In contrast a centrifugal clutch will only be one fixed gear ratio, providing no gear reduction or overdrive.

Ok now moving on from my poor explanation. ( i apologize for not being clearer and more descriptive).
Let's talk about pros and cons of each.

Centrifugal clutch pros.
1. The average riders clutch cost around from 30 dollars to 100 for a drum clutch providing for a cost effective drive system

2. Clutches do not have belts that wear out but they do require basic maintenance.

3. There is no torque loss when the clutch is fully engaged. This means maximum power transfer to the wheels.

4. When at cruising speed and you floor it, the acceleration and "pull" will feel more direct and instant. There is no belt slip so you have better cruising speed acceleration.

5. Higher top speed potential due to better power transfer.

6. Simple to install

7. Slighly better water resistance.

8. Although it is not recommended unless you have a fool proof chain tensioning system that wont allow the chain to fall off, you can use a the outside clutch drum with a clucth band brake to provide a braking system.

9. Band brake setups on the clutch provide better braking power due to the gear reduction of the sprockets.

Centrifugal clutch cons.
1. With a tall gear ratio acceleration and off road ability will be comprised
2. Always a trade off between torque and speed
3. Driving at slow speeds when the clutch is not engaged will build up heat and destroy the springs and clutch shoes.
4. Faliure to oil the clutch will cause it to stay engaged and the machine will creep at idle.
5. Reapeatedly destroying clutches and buying more is more expensive than buying a torque converter.
6. If oil gets on the shoes, it can slip more and build up more unwanted heat.
7. Inexperienced riders will typically drive slower and cause the clutch to partially engage and causes premature wear.

Torque Converter Pros
1. Much better versatility in riding styles. You dont have to change gearing for a certain riding environment
2. Acceleration from a stop will be much better than a centrifugal clutch.
3. You can haul more weight at a higher speed than a clucth
4. Low maintenance
5. Almost weather proof.
6. You can pull much taller gearing without harming the drive system
7. Speed is generally increased
8. Much more customizable and tunable.
9. Less costly drive system over time.
10. Can handle higher power levels than a clutch.

Torque Converter cons.
1. Initial price is higher but it is worth it over all.
2. Water on the belt will cause slip and loss of power
3. Slighly less power transfer efficiency.
4. Cruising speed acceleration is not as strong as a centrifugal clutch.
5. Belts can burn if to much load is applied to the system.


Riding conditions
Centrifugal clutches are better for racing and street use where every last ounce of power is desired. If you racing on the street get a clucth. If you want to offroad today and ride on the street tm and ride in different conditions daily, get a torque converter.
A clutch can offroad regardless of what people say. It depends on your gearing and like i said its a trade off between torque and speed.

Sorry if i missed anything and if i didnt explain everything clearly. I tried as hard as i could too. If you have any other information to contribute to this please comment on this thread.

Have a good day everyone and ride hard.
 

race

Active Member
#3
Thanks for the info.

Thought I had heard Torque Converters didn't like a dirt environment? Getting dirt on the belt, etc. causes slippage?

How do you set the high and the low on a torque converter? And are there inboard / outboard spacing issues?
 
#4
No they dont like sand or dirt that much. It seems to wear the belt really fast so if you have a cover for it keep it on. I think when you say high and low your refering to gearing. The highest and lowest gear is basically derermined by the pulleys maximum and minimum size. The lowest gear for the torque converter itself (talking about a 30 series with a 6 inch driven) is 2.7 to 1 and the highest gear is .9 to 1. But keep in mind those ratios are just for the cvt. Your overall ratio at will depend on what gearing you have. Check this cool gearing calculator if your interested.

http://app.kartcalc.net/#page-3
 

Dick DeBuse

Active Member
#5
Centrifugal clutches: There are many more designs in addition to the "garter spring" system you describe. Some better, some worse. Many use spring-loaded semi-circular "shoes". Some have linings on the drum, some on the shoes. Some early clutches used bronze shoes and no lining. There are belt type centrifugal clutches, including some torque converter drive units that may be used as clutches. The original V-Plex variable diameter belt clutch can also function as a torque converter if a spring loaded tension pulley is provided.
Torque Converters: Again, many designs. Some speed sensitive, some torque sensitive. Early units were advertised as "self-shifting transmissions". Which is a good description. A torque converter is a 2 pulley, belt drive system with at least one pulley capable of variable diameter. Salsbury pioneered the use of steel balls for flyweights to operate the variable diameter sheave. Some Salsbury industrial units (such as those used on concrete buggies) had separate clutch and variable diameter pulley systems. The earliest torque converters may have been fluid drive units that were used on washing machines so they could be started under load (full of clothes and water). A small gas engine has a limited operating range. A torque converter can triple that range.
Cost: Probably the most important issue. Nothing is cheaper than a single speed clutch. A torque converter that can withstand carrying 2000# loads of concrete up 25% slopes all day will cost more than your whole mini bike. Same for snowmobile drives. A clutch for go karts or torque converter for junior dragsters can be very tempting.
 
#6
One thing I forgot mention is the weight of the machine and the ability to pull weight. Now were are going to compare the two drive systems in that aspect. Lets use a baja warrior for examples. So the baja has:
19 inch tires
6.5 HP @3600
10 tooth clutch, to a 20 tooth and 10 tooth jackshaft sprocket to a 50 tooth rear sprocket.
This gives us a 10 to 1 gear ratio and a top speed of about 20 mph. Which isnt that impressive but the wheel torque is. Maximum wheel torque at peak power is 94.85 ft lbs. So we dont have speed but we have torque. With this ratio we can climb hills and offroad but street riding will suffer. Substitute a 10 tooth for a 20 tooth will halve the ratio, turning it into a 5 to 1 ration. You will half the wheel torque but twice the speed now at about 40mph.

Now lets compare the wheel torque with a torque converter. We are using the same information, except now we are using a comet 30 series with a 10 tooth jackshaft sprocket instead of a clutch.

Our max wheel torque is now 128ft lbs.
The minimum wheel torque is 42ft lbs. In now instead of the jackshaft set with a fixed ratio of 10 to 1 we now have low ratio 13.5 to 1(even lower than before) and our high ratio is 4.5 to 1 with a infinite amount of ratios bewteen the two. So this cvt provides much more versatility in gearing and gives you torque and speed, with out sacrificing one for the other.

As you can see the torque conveter will be able to pull a heavier machine much easier and faster do the variable ratio feature. Your basically making your powerband much more usable and "wider" allowing you to trail ride and then rock 50mph down the road instead of having to change gearing with a clutch.
 
Top