I am hoping yall can give me some guidance quickly. I just finished another weekend at COTA, all went very good all weekend until the last freakin 5 minutes. I was coming off track in my last Sunday session, just entering paddock, and something happened to the clutch. It started making a loud rattling sound, and I could feel a distinct change in pedal, it depressed about 1/2 way, and remaining was like a gear mis-meshing feel thru the pedal. A couple things to consider:
- When I turned into the paddock in 2nd gear, for some stupid reason I depressed the clutch confused if I was stopping for upcoming traffic or down shifting to 1st gear. Regardless, I would never have though depressing the clutch at any time would have hurt anything.
- The water temp was hot, about 88C, and oil at 100C. I should have removed more tape prior to last session.
- After getting out the car and thinking about it, I restarted it to test it (still in paddock). Pedal still felt same with something wrong with clutch. Can still rolls freely in Neutral though.
- After getting home, I retried it again, same pedal feel. Can actually hear a rattle when pushing it around.
Any ideas what is going on? I need a quick fix as heading on long road trip to Road Atlanta and Barbers in 2.5 weeks from Texas.
raider89, using the clutch like that is normal use and shouldn’t cause any issues. I would recommend giving your Radical dealer a call. With that said, If you want to do some trouble shooting I would start with the rod that goes from the clutch slave cylinder to the clutch. I recall another Registry member had a similar issue and if I recall properly it was a bearing or bushing that supports that rod that failed that was the problem. This isn’t a common issue, but it does happen. The bad news is that if it is this it requires the engine to be overhauled. The good news is that from your other post it looks like it is time for your engine to be overhauled.
Hopefully this isn’t your issue, but here is the post I was referring to. https://radicalsportscarregistry.com/radicalforum/sr3-specific-discussions/bearing-failure/#post-6229
That does not sound good
With Charley on this, remove the clutch slave cylinder and check the push rod. This sounds like the small bearing that the input shaft runs in has collapsed - the clutch push rod runs through the middle of this.
If this is the case do not run the engine anymore and get it rebuilt, when this bearing fails it allows the input shaft to move out of place so the gearbox is running out of line.
Update: I just returned from being out of town for work and wanted to drain the engine oil and oil filter for quick inspection of any metal particles. Wow, loaded, I could tell I have a big problem the second I removed the sump drain plug (even before filtering the oil and dissecting the filter). Regardless, engine R&R coming via local dealer shortly.
So, this was noted above as being a rare failure. Is there something I did that caused it? I sure would like to better understand the root cause to prevent it after the rebuild. It still amazes me there were no apparent indicators while on track, but upon returning to paddock.
in hindsight, could this have been damaged during a prior spin somehow? I have had ~6 spins in this car at various speeds over my first year. One very unexpected one was the prior session that day. I think I am quick to depress the clutch, but maybe missed it by a fraction.
@raider89, I haven't heard of any systemic cause for this failure and I suspect that nothing that you did caused the failure. Perhaps @RLM-dan had more details? It is my understanding that this just happens on some engines, almost exclusively on 1500's but there have been some 1340's also. Radical makes periodic upgrades to these engines based on what they learn on the track and it is my understanding that there is an upgrade to this area that is just about to be released. So when your engine is rebuilt you shouldn't have this problem again.
my car does not have the spin safe clutch. Can someone explain the mechanics of how that operates? I am assuming it is purely internal, thus should I consider getting this modification during the upcoming rebuild?
@raider89 ... I switched to the 'Spin Safe'/Rekluse clutch when I put a new engine in last November. On it's third event and at this stage I wouldn't go back to the standard solution.
The sprint racing and hillclimb events I do with this car require standing starts, and that's the main reason for me changing. I just couldn't get reliable enough starts (bogging down too much, flaring the clutch or spinning the rear wheels.... there's just not enough 'flywheel effect' with these engines, and almost no torque at low throttle opening before the clutch closes)
Since putting in the Rekluse clutch I haven't had any issues, and starts have been very repeatable. Might not be as fast ultimately as my best start with the normal clutch, but works every time, and is fairly close.
The only slightly tricky thing is checking/setting the 'free play gain' which is an adjustment that you make on their slave cylinder (the reason they need you to change from the Radical unit). It simply allows you to adjust the location of clutch push rod (in or out) by turning a screw in the back of the slave cylinder, which effectively changes the clearance inside the clutch stack.
I had to adjust mine fairly regularly during the first event (takes about 5 minutes in between races), but has not needed adjustment as much since then. I suspect it had fully 'bedded in' now...?
It is internal, plus there is a new billet slave cylinder that replacers the Radical slave cylinder on the right hand side of the engine - bolts on similarly to the Radical unit.
The clutch assembly itself is interesting. It's effectively an 'automatic' clutch assembly that fits inside the normal clutch area. It comes with a similar set of clutch plates (alternating steel and friction material rings) to the normal clutch... but then you add an additional 'ESP' ring assembly. I haven't had the assembly apart, but the ESP ring is about 14 or 15mm thick, and is basically two aluminium rings, that have friction material bonded on their faces. In between these aluminium rings there are some (6 I think) 'wedges' that are loaded by the centripedal force as the clutch/engine revs rise. This pushes the two aluminium plates apart, effectively closing the clutch plates, forcing the clutch stack to transmit the drive. The ESP assembly has 6 springs inside (that can be changed to adjust the 'take-up' revs)
I changed it myself - took about 2 hours, but I was very careful to check and follow the instructions supplied. Could do the next one easily in 90 minutes.
They are used a lot on motorbikes, both road and dirt bikes. You can find plenty of video's online on how they work.
The only slightly tricky thing is checking/setting the 'free play gain' which is an adjustment that you make on their slave cylinder
That is a fact. I spun and burned one of these on the first day of use because of improper adjustment and bed-in procedure. On the subsequent clutch, we paid close attention to the bed-in and adjustment for the first two days and now needs no adjustment, however each time I get in the car I check that that there a very slight drop in RPM when I release the clutch, but not so much that the car pulls forward.
Another key benefit of the spin-safe clutch is that it is *spin-safe*. I left-foot brake, so it is often difficult and/or dangerous to get off the brake, move left and right foot over during a spin to grab the clutch and brake before the starter disintegrates by rolling backwards.
Dan-
i just had the same set of conditions. Higher water temp as I had taped some of both intakes for first cold session of fall and pressed in clutch while in 2nd coming into paddock. Same results with clutch engagement noise and feel. I can see a bent or out of alignment clutch slave cylinder engagement pin/rod.
was yours also bent or out of position and did you ultimately get a root cause from the engine rebuilder?
I did not look that close because I drained the oil and it was full of metal. The clutch bearing split prompting full engine rebuild. A few bad parts shown below.
Hi Christian... probably bad news based on the photos you've posted, but I suspect you have experienced this failure... seems to be fairly common, and according to some engine builders maybe even more common in the last few years...
I'm having one of my RPE1500 engines overhauled at the moment, and here is the 'input shaft' that came out of it. It has the early signs of this failure that I suspect you have had.
This shaft has 'spalling' starting to occur, which leads to the roller bearing failure that has probably caused your issues.
The shaft is the 'input shaft' and the journal that's shown above is only about 20mm in diameter.... and the whole shaft is hollow. The clutch push rod that's bent on your engine runs through this shaft and pushes another rod that actuates the clutch that is mounted to the other end of this shaft.
Here's a picture of a new shaft, with another showing the journal as well as one of the bearings that goes on that end.
What apparently happens is that once the 'spalling' starts on the journal, then the rollers in the bearing that run directly on that surface cop a real hammering (literally) causing the roller bearing to fail and that allows the shaft to move sideways at that end.... and I fear that is why your clutch push-rod is bent and off centre to the bearing journal position in the gear case. (The failure of that bearing also causes the whole input shaft alignment to be lost and can cause damage to all the gears that are on it and I guess the other 'mating' gears in the box as well....hopefully you have caught it early)
This same bearing/shaft is apparently what Radical are now modifying with their '1500-X' engines and rebuild upgrades, that requires the use of the 15W60 Motul oil (instead of the previously specified 15W50), and also suggests that we run our engine oil hotter by 5 to 10 degrees C.
I actually hope it is not this problem in your case, but based on what I'm learning about these engines I would put a fair bet on this being the root cause....
Thanks!
we’ll soon find out. Since I’m nearing the life of the engine and planned a winter rebuild I’m just loosing out on a few fall sessions - unless more damage was done internally. We’ll find out from SM.
