Post by tasilloracing76 on Jan 24, 2006 17:19:34 GMT -5
The Drivetrain - where the rubber almost meets the road.
An area of great concern is from the driveshaft on the side of the engine down to the rear axle. Other than wrecking, this area takes more of a pounding than any other set of components on the Slingshot. Everytime you accelerate or decelerate, tremendous force is taken up by the drive train. For this reason, you need to pay special attention to the clutch, chain, and sprocket.
Since the change from 35 to 40 chain, we have alway ran the Noram 1800 clutch. No particular reason other than it was more available at the time the 40 chain became mandated. I'd love to see a debate here on which clutch is better. My feeling is that the Noram works just as well provided it is serviced regularly. The driver is integral to the clutch drum and cannot be changed as the driver on the Tobias clutch can. Also, the Tobias driver is a harder steel and perhaps wears better. We get almost exactly 1 season out of a Noram clutch drum. They run around $80 to replace.
The two biggest areas to be fussy about is the chain alignment and the chain tension. Too tight wastes horsepower. Too loose means tossing the chain in a collision or very sudden stop. when aligning the engine, here's what we watch for:
We start with the engine mounting bolts loose and positioning the engine to align the clutch driver with the sprocket. The chain is on both of them and we snug it up. We then tighten the 4 engine mounting bolts to lightly snug the engine down on the swing arm.
The object here is to manually spin the rear wheels while watching the chain on the driver and sprocket from 'directly behind'. A properly centered chain will wander back and forth across the clutch driver. There is enough side play in the clutch to allow the chain to do this. It is also very important that the engine is not misaligned relative to the sprocket. If this is the case, you will not notice any wandering and there will be more frictional noise coming from the chain on the gears. Once we tighten the engine mounting bolts down; things may change as the engine conforms further to the swingarm assembly. This will generally either tighten or loosen the chain beyond what you consider acceptable. You get a feel for this with experience and we tighten the engine bolts in a pattern that minimizes this on 'our' car. You need to find the right combination for your car. When everything is right, there will be around 1/2 to 3/4 inch of slack movement on the chain and the chain will track such that it wanders back and forth on the clutch driver. The wheels should turn freely and there should be minimal noise from the chain / gears.
Another possible problem is that the chain will tighten and loosen as you revolve the sprocket 180 degrees. It doesn't take much tolerance error in the sprocket hub or the axle or the sprocket itself to cause this. We have very slightly opened up the holes in our sprockets so that if this occurs, we break the 6 sprocket mounting nuts and spin the rear wheel while taking up some slack
on the chain. Again, this is more of an art than a science but it allows the sprocket to self center. We then very carefully without disturbing the resulting position; tighten the 6 sprocket nuts back up and have been pretty successful at equalizing the chain tension as the rear wheel is turned. DO NOT open up the holes any more than a wee bit !
Regarding the clutch itself, 2 problems come to mind; clutch slip and spring tension. We keep our idle at exactly 1500 RPM such that the clutch shoes are not contacting the drum in idle. They generally engage around 1800 RPM with the spec springs. Excessive RPM will cause the shoes to partially engage and polish the clutch drum which results in clutch slip. The telltale sign of this is when the engine RPMs are up but your speed is not there. It is most evident as the car is pulling out of the pits or during the restarts. You have to listen to the engine which will be rev'ing faster than you are used to as the car is pulling away. The fix is to sand the inside of the clutch drum to rough it up and in addition, we gently take a wire brush to the clutch shoes to break the glaze. NEVER get WD40, or oil or any other lubricant on the clutch drum or you'll have a near impossible task of getting it back to normal.
As the clutch shoes wear, the clutch springs need to extend farther for the shoes to engage the drum. After a while and given the heat the springs are subjected to, they tend to lose tension. When this happens, the shoes are chattering and polishing themselves. Also be vigilant for broken springs. You need to have the clutch apart to spot this. We disassemble the clutch around every 5 races, rough up the drum, repack the needle bearings, clean out the dust, and replace the clutch springs.
After every race we inspect the chain for any binding, test the length such that it has not stretched too far (which will result in premature wear of the clutch driver. ) We clean the chain in WD40 and wipe off the excess. Finally we use a good quality chain lube after every run on the track.
Finally, be aware that the engine shaft goes through incredible fatigue. This is known as fully reversing fatigue wear. Every shaft rotation, the shaft goes through a compression and a expansion cycle. Eventually, a surface microcrack will form and continue to grow until the shaft is compromised. Tobias now offers an outrigger which will support the end of the "Tobias Clutch" and prevent this loading on the shaft. There is no option offered for the Noram clutch at this time.
An area of great concern is from the driveshaft on the side of the engine down to the rear axle. Other than wrecking, this area takes more of a pounding than any other set of components on the Slingshot. Everytime you accelerate or decelerate, tremendous force is taken up by the drive train. For this reason, you need to pay special attention to the clutch, chain, and sprocket.
Since the change from 35 to 40 chain, we have alway ran the Noram 1800 clutch. No particular reason other than it was more available at the time the 40 chain became mandated. I'd love to see a debate here on which clutch is better. My feeling is that the Noram works just as well provided it is serviced regularly. The driver is integral to the clutch drum and cannot be changed as the driver on the Tobias clutch can. Also, the Tobias driver is a harder steel and perhaps wears better. We get almost exactly 1 season out of a Noram clutch drum. They run around $80 to replace.
The two biggest areas to be fussy about is the chain alignment and the chain tension. Too tight wastes horsepower. Too loose means tossing the chain in a collision or very sudden stop. when aligning the engine, here's what we watch for:
We start with the engine mounting bolts loose and positioning the engine to align the clutch driver with the sprocket. The chain is on both of them and we snug it up. We then tighten the 4 engine mounting bolts to lightly snug the engine down on the swing arm.
The object here is to manually spin the rear wheels while watching the chain on the driver and sprocket from 'directly behind'. A properly centered chain will wander back and forth across the clutch driver. There is enough side play in the clutch to allow the chain to do this. It is also very important that the engine is not misaligned relative to the sprocket. If this is the case, you will not notice any wandering and there will be more frictional noise coming from the chain on the gears. Once we tighten the engine mounting bolts down; things may change as the engine conforms further to the swingarm assembly. This will generally either tighten or loosen the chain beyond what you consider acceptable. You get a feel for this with experience and we tighten the engine bolts in a pattern that minimizes this on 'our' car. You need to find the right combination for your car. When everything is right, there will be around 1/2 to 3/4 inch of slack movement on the chain and the chain will track such that it wanders back and forth on the clutch driver. The wheels should turn freely and there should be minimal noise from the chain / gears.
Another possible problem is that the chain will tighten and loosen as you revolve the sprocket 180 degrees. It doesn't take much tolerance error in the sprocket hub or the axle or the sprocket itself to cause this. We have very slightly opened up the holes in our sprockets so that if this occurs, we break the 6 sprocket mounting nuts and spin the rear wheel while taking up some slack
on the chain. Again, this is more of an art than a science but it allows the sprocket to self center. We then very carefully without disturbing the resulting position; tighten the 6 sprocket nuts back up and have been pretty successful at equalizing the chain tension as the rear wheel is turned. DO NOT open up the holes any more than a wee bit !
Regarding the clutch itself, 2 problems come to mind; clutch slip and spring tension. We keep our idle at exactly 1500 RPM such that the clutch shoes are not contacting the drum in idle. They generally engage around 1800 RPM with the spec springs. Excessive RPM will cause the shoes to partially engage and polish the clutch drum which results in clutch slip. The telltale sign of this is when the engine RPMs are up but your speed is not there. It is most evident as the car is pulling out of the pits or during the restarts. You have to listen to the engine which will be rev'ing faster than you are used to as the car is pulling away. The fix is to sand the inside of the clutch drum to rough it up and in addition, we gently take a wire brush to the clutch shoes to break the glaze. NEVER get WD40, or oil or any other lubricant on the clutch drum or you'll have a near impossible task of getting it back to normal.
As the clutch shoes wear, the clutch springs need to extend farther for the shoes to engage the drum. After a while and given the heat the springs are subjected to, they tend to lose tension. When this happens, the shoes are chattering and polishing themselves. Also be vigilant for broken springs. You need to have the clutch apart to spot this. We disassemble the clutch around every 5 races, rough up the drum, repack the needle bearings, clean out the dust, and replace the clutch springs.
After every race we inspect the chain for any binding, test the length such that it has not stretched too far (which will result in premature wear of the clutch driver. ) We clean the chain in WD40 and wipe off the excess. Finally we use a good quality chain lube after every run on the track.
Finally, be aware that the engine shaft goes through incredible fatigue. This is known as fully reversing fatigue wear. Every shaft rotation, the shaft goes through a compression and a expansion cycle. Eventually, a surface microcrack will form and continue to grow until the shaft is compromised. Tobias now offers an outrigger which will support the end of the "Tobias Clutch" and prevent this loading on the shaft. There is no option offered for the Noram clutch at this time.