EFE Clutch

[markfoggy]

So if we fit the modified/stronger back plate kit and welded rivets, still shits itself, what do I do next.

Phase One Endurance life expectancy of the springs climbing out of the backing plate/basket is less than 8 Hrs racing. As we all know, when a spring escapes we're talking total carnage. Last one took out the oil pump drive on it's way out of the cases so the head and barrels died before we could catch it. As I think you're all aware there are not enough of these on the planet for us to make this mistake again. 

Ok,  we give a new basket to every race!  Not exactly a solution, though.

Now it appears that the issue is about the spring diameter growth, wearing into the back plate.

2 Questioms,

has anybody tried reducing the slots in the Gear Wheel (I'm thinking custom built 'rivets'), to limit the clutch cush drive. And does this just knock the forces into the shafts and destroy the cases.

Or has anybody tried building up the backing plate where the springs are trying to escape from,  I'm thinking a run of weld might help, but fook knows what the resultant wear properties of the steel component are likely to be if I try getting Biblical on it's arse.

Make that 3 Questions, different springs?

 

Ideas welcome.

 

[Gixer1460]

Sorry?.......what the hell are you doing to your clutches to destroy billet backplates in 8 hours? I've seen springs loosen after a season or so of drag racing with Pro Mod spec engines and big slicks but never lost a back plate!

[markfoggy]

Mental isn't it.

All we're doing is circuit racing, and we're using Nova boxes. No quick shifters, nothing that could increase loads considerably and yes we have got a cush drive between the sprocket and back wheel, but probably slightly more rudimentary than the standard stuff. We are also really careful with rider selection and advising them. We cannot afford to over-rev the things on the down-change, we need the longevity to get 4 hour races completed without the valves sticking to the underside of the tank.

I should really have some photos to help with this, but what we're finding is that as the springs are growing in diameter due to compression, they are eating up through the chamfer on the backing plate and threatening to escape. One has at Spa, engine recoverable components were the fasteners and a couple of engine side covers. This seems to be more on the acceleration loaded end of the slots , than the deceleration, but there is some wear here as well. Now as it goes, we are sticking with the standard helical gears, 'cause we like how EFE's etc are manufactured, the tolerances are really good, certainly better than the work that we've seen from crank assemblers, so far. This is the only area where I can think of where you'd generate a side load and on inspection, the rivets and spaces are tightly toleranced so this shouldn't be an issue. 

Now these are pretty simple components, so we'll rule out assembly error for the moment. It's just getting expensive and time consuming given that we have to get them TIG welded off-site.

Now I know that we're using some stoopidly fast riders and going some distance at a pace that isn't often reached by many, but even so.

[Arttu]

Sounds a bit strange indeed. Generally a clutch with HD back plate should be very durable. On the other hand you probably get more compression cycles during one circuit race than in several years of drag racing. But these work fine also in street use where they collect some serious running hours over the years. For example I haven't had any problems during last five years and maybe 20-30 thousand kilometers. Of course it has been mostly quite easy riding but I also use all 300hp on regular basis.

I'm still wondering if side load from the helical gears could affect to this. You are right that rivets should take the load but still... Do you mean that stock cranks are manufactured with better tolerances than what you can get from the crank builders? If I recall correctly the Suzuki specification for crank throw-out is 0.1mm and according the crank builder that I have been using stock cranks often exceed even that. He assembles the cranks within 0.05mm which should be good for pretty much everything.

 

[Gixer1460]

"but what we're finding is that as the springs are growing in diameter due to compression, they are eating up through the chamfer on the backing plate and threatening to escape".

Odd / strange comment as the springs shouldn't change diameter - they compress on to themselves then coil bind with no more movement - but there shouldn't be that much movement ie. spring should be under compression when fitted static!

Couple of items to check - the rivets are different between the GS1100 and the GS1150 - 0.9mm difference in dia..... could you be using the wrong ones? Clutch hub nut is made of cheese (relatively speaking) and can distort allowing the hub to wobble, although how this loosens the springs is anyone's guess! If you are using clutchless changes then there shouldn't be much shock loading to deal with - how about throwing the springs away and use alloy dowels instead of in the cavites?

[markfoggy]

Sorry about the odd/strange comments. I ought to remember that Springs, being things of engineering wonder, have a property similar to Shroedinger's Cat, where some of their mass/volume is able to slink off to an alternative parallel universe when a load is applied. Safe to say they are pre-loaded on fitment, comes as a kit after all, though we did receive a mismatched set of springs recently. there should be 3 short and 3 long, we received 6 short.

Will be checking those dims though. We're purchasing model specific, but stranger things have happened between supplier and end user. Most recent one that I inspected, tolerance of spacer fit to gear slot was very accurate. Hub nuts appear to be fine, not displaying any tendency to spall up on removal and eat their threads, which would point at distortion. 

I'm all for machining up oval spacers (in place of the supplied ones)  that would limit the extent of spring compression by limiting the available travel between primary gear and hub/backplate assembly. I'm also quite keen on the idea of  filling the slots in the primary gear with an elastic material, around the spacer, this should act as a damper, though I can't think of a material that would survive the part where the rivet is TIGed to the back plate. Locking it solid here with those dowels I'm less keen on. My suspicion is that all we'd accomplish is a transfer of the loads  from the gearbox input bearing into the cases leading to wear that ended up with the cases failing as the bearing span, in fact it could end up being more violent that that.

Real head scratcher this one.

 

[teltwosheds]

I'm no engineer so I would opt for using a quick shifter and see how it goes from there. Am I right in assuming the shaft bearing retaining ring is not showing signs of movement ?

[markfoggy]

I think quickshifters are banned from the regulations to which we must adhere  (hmmm, shuffle, looks sideways, applies thou shalt not get caught unless you can find someone else using them).

Temptation here is to fit a Sigma Slipper ( Katana) clutch which might alleviate some of the problems, though they do utilise the standard outer basket, so possibly gets us nowhere. This would be stretching the limits of the law and we do believe in keeping things mainly legal.

Only other wear that seems apparent is within the basket itself as we're seeing inadequate lube to the rear most plates. We've pointed out that not having a drill way through the input shaft of the Nova gearbox is an error on their part. Hoping to see a resolution to this soon.

[markfoggy]

Just to add, the quickshifter option is something that we probably wouldn't do on reliability grounds. Getting a truly reliable (in our terms) system would probably depend on us being able to interrupt inside a solid state device. I don't know of an electronic  ignition that would allow this, certainly up for offers if anybody can think of a solution. I've been looking at the 2 stage Dyna  ignition pack that we could piggyback into what we've got at the moment. Dyna 3000 is it, the one that lets you set a control rev for launch. I'm thinking that we could program this easily enough for a pit-lane limiter, but I'm a bit of a ludite when keeping the smoke in the wires is a priority.

[teltwosheds]

Well lets hope the oil feed resolution resolves it .

I get the smoke bit. Any idiot knows the magic smoke keeps the electrikery ticking 

[markfoggy]

Sorry definitely not an oil feed issue.

[coombehouse]

Just to add, the quickshifter option is something that we probably wouldn't do on reliability grounds. Getting a truly reliable (in our terms) system would probably depend on us being able to interrupt inside a solid state device. I don't know of an electronic  ignition that would allow this, certainly up for offers if anybody can think of a solution. I've been looking at the 2 stage Dyna  ignition pack that we could piggyback into what we've got at the moment. Dyna 3000 is it, the one that lets you set a control rev for launch. I'm thinking that we could program this easily enough for a pit-lane limiter, but I'm a bit of a ludite when keeping the smoke in the wires is a priority.

Ignitech ignition systems have a built in quickshift function on their basic programmable kit & its cheap too. Allows for 3D ignition mapping in conjunction with a TPS. I have used one & it worked fine though the gearbox didnt like it at all & I think a selector is now bent. I took it off in the end & now use Microsquirt.

Back to your clutch failure, what actually broke? Did the rivets give up or the back plate break or distort or did the springs just exit through the rectangular window?

Nick

 

[Gammaboy]

I have heard of the "heavy duty" backing plates wearing through the chamfer before - the folded tangs on the stocker are better in this regard.

CNC a backing plate with pockets for the springs that are fully enclosed and ship it off for heat treatment? will stop the springs escaping, but will make inspection harder!