clutches

Clutches are there in different styles.

Swing clutches

There are 2-3-4 and even 5 shoe swing clutches. The common one used is the 3 shoe Serpent style clutch, where each shoe has its own scisors return spring.

When the engine rev's up the shoe will go outwards due to the rotating mass and will engage the crankshaft with the clutch bell. 
As soon the engine is below a certain number of rev's the clutch will disengage. 
The shoe returns to their rest position with the help of the return springs.
The spring on each shoe also prevents that the car is crawling when the engine is running at the idling speed.
The lighter the weight of the shoes the later the clutch will engage.
The heavier the shoes are the sooner the clutch will engage.
Also the length and wire diamater of the return spring determines if the clutch shoe engages earlier or later.

Shoes are wearing and also the springs can break after a while or become weaker. Check for the shoes wear every 5 competitions by taking off the clutch bell. Also check the ball bearings in the clutch bell after each race. Needle bearings will last longer then ball bearings, but the radial play in a needle bearing is a little bit higher. For normal use oil the ball bearings every race with some Teflon oil.

If the engine of your car is running on the lowest possible idling speed, but the car still wants to move forward (crawl) check for a broken or weakened return spring or the shoes are too heavy. With a good clutch the wheels will not rotate even when the car is lifted from the ground.

For almost every buggy engine used these days, it is best to engage a tittle later, because of the higher rev's these engines can produce. This will give more bottom power. Modify the shoes as showed below by try and error method. Original Serpent shoes need maximum one hole as they are already lightened from the factory. Mugen and Kyosho need to be modified with one or two holes depending of the weight and engine performance.

If shoes are too heavy just drill one or two small holes with a +/- 3 m/m diameter at the end of each shoe (see the marked spots). This will make them lighter and the clutch will engage later.

It is not advisable to use Centax or Synchro clutches in a 1:8 buggy, due to the high loads coming from the drive train, they need to be adjusted and rebuild too often. Also the clutch is very aggressive if you compare it with the normal style clutch.

!TIP!
Never remove the flywheel by slamming with a object on the rear of the flywheel.  
This will cause puts in the main bearing seating and cause premature main bearing failure. The right way to remove the flywheel is to place the rear of the flywheel on a solid object and placing a piece of wood or nylon on top of the cranckshaft. Then you may hit the wood or nylon without damaging the bearings. Or use a special tool to pull off the flywheel.

CLUTCH BEARING TROUBLE SHOOTING:
Constantly blowing clutch bearings?  It can be a tough problem to eliminate.  Here are the most common causes & solutions:

1] Is the clutch bell hitting the chassis when it flexes?  Look closely directly under the bell for a rub mark.  If it comes in contact with the chassis at all this can cause blown bearings.  The solution here is to use better braces to keep the chassis from flexing.  If this isn't possible or a quick fix is needed at the track shims/washers can also be used to raise the entire engine assembly a little.

2] One of the most common causes of clutch bearing failure is improper lubrication. Soaking them in any type of oil is a mistake. Once it heats up the oil migrates down the shaft into the clutch = heat = toasted bearings. I use a high melt temp extreme pressure grease in all the sealed bearings. This grease is designed for extreme bearing applications and does not migrate at operating temperatures. Many racers also have success cleaning all the lube out of the clutch bearings then re-oiling with one-half to one drop of Mobil 1/Prolong/etc.

3] Is the clutch assembly getting too hot? Many clutch bells turn into a blue color instead of normal black when overheated.  If one is available use a temp gun at the end of a hard run.  An excessive temperature at the front of the bell indicates resistance or a vibration problem.  At installation the bell should spin completely free and there should be a little "play" (about 0.5 mm).  This allows the parts to expand when they heat up without binding. Other possible causes of excessive heat are a clutch spring that has become weak (allowing one shoe to constantly drag) or a worn or broken clutch shoe. 

4] Check both engine bearings. Play in either will cause clutch bearing wear by allowing the crankshaft to vibrate at high RPMs. If the front engine bearing leaks fuel this can migrate into the clutch causing the failure.

5] A slightly warped crankshaft can also vibrate clutch bearings to death quickly.  This is the most difficult problem to run down since the shaft does not have to be noticeably warped to cause bearing damaging vibration at high RPM.

6] The clutch bell itself can also be a bearing eater if it has developed an out-of-round (warped) condition or has been manufactured out-of-tolerance. I've seen some famous brand bells with this problem right out of the package.  The outer bell spins perfectly round but the inner bell (with the teeth) is warped.

Some of these items can be identified and eliminated easily, keep in mind
that the easy & dependable way to isolate these problems is to replace the
engine (including the clutch/flywheel assembly) and see if the problem
persists.

Article by Bill Riggins

HOW TO BUILD YOUR ENGINE
	All parts to build the engine
	These three parts are mounted first. Bronze cone, flywheel and cranckshaft nut.
	First slide the bronze flywheel cone cranckshaft until it hits the inner shield of the front engine bearing.
	Now mount the flywheel and then the cranckshaft nut. Watch that there is a part inside the nut with less thread. Do this part first on the cranckshaft. (the thicker part first).
	To ensure the flywheel does not comes of when starting the engine tight the cranckshaft nut with these tools very well. I do not use thread lock but you can use some.
	First I drilled a hole (red marked) in every clutch shoe of 3 m/m diameter to lighten the clutch shoe. This will engage the clutch a little later that is better for the engines we use now a days. If you like to keep it standard at first no problem as you can always do it at a later time.
	Fit the shoe spring in the outside groove just like in the pic.
	Now mount the shoe with the spring as showed on the clutch pin. Be sure the small part of the clutch spring will be in the rounded carved part of the cranckshaft nut.
	Place a hexagon tool like this when the second shoe is mounted too.
	Then you can fit the third and last shoe very easily.
	So it should look like this. Be sure that the small parts of the shoe springs are in the carved groove of the cranckshaft nut.
	Now you can fit the first 5x10x4 m/m bearing onto the shaft.
	The other bearing is placed in the outside of the clutch bell.
	Slide the clutch bell on the shaft and secure the clutch bell with a 3 m/m hexagon screw. In my case the proper length was not in the kit. So I had to use the one that comes with the engine. Be sure to use a small washer to keep the clutch on the shaft. Also some thin shim washers might be needed to remove excessive play. A play of 0.5 m/m is needed.
	Put the at each side two 3x20 m/m screws.
	Slide one of the engine mounts over the two screws and secure them with a 3 m/m lock nut.
	This is how it should look if both sides are ready. Do not tight the screws completely but keep the engine brackets moving on the mounts.
	These four flathead 5x10 m/m hexagon screws are needed to secure the engine mounts to the chassis.
	Fit them from the bottom but do not tight them completely yet
	Now move the engine so the clutch bell is running in the middle of the main gear. Then first tight the four black 3x20 m/m screws. Then the four bottom screws might be tightened.
	Adjust the play between the clutch bell and the main gear (red marked) by letting +/- 0.5 m/m of space. This is a try and error job for a later stage when the wheels are mounted!

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