Lots of testing and believe we have the offset nailed down

[twiz28]

I'm about to go through this exercise of pulling stub shafts in the next week on 2 occasional belt blowers, kind of can blow one if you want to scenario. I cant understand why some sort of snap or retaining ring has not been designed in to stop this bearing walking in from happening. I'm expecting to have to machine a couple of mm off the secondary shaft to hit the sweet spot. As I understand the plug has to be machined the same amount, correct??

 

[1nc 2000]

Removing the stub shaft bearing from the housing and green loctiting it in place is preventive maintenance in my book.
If or when you blow a belt it won't move your shaft in.

 

[yamamarc]

I'm about to go through this exercise of pulling stub shafts in the next week on 2 occasional belt blowers, kind of can blow one if you want to scenario. I cant understand why some sort of snap or retaining ring has not been designed in to stop this bearing walking in from happening. I'm expecting to have to machine a couple of mm off the secondary shaft to hit the sweet spot. As I understand the plug has to be machined the same amount, correct??

Yes..

 

[fatchance]

I'm about to go through this exercise of pulling stub shafts in the next week on 2 occasional belt blowers, kind of can blow one if you want to scenario. I cant understand why some sort of snap or retaining ring has not been designed in to stop this bearing walking in from happening. I'm expecting to have to machine a couple of mm off the secondary shaft to hit the sweet spot. As I understand the plug has to be machined the same amount, correct??

It's not a difficult process at all, 30 minutes maybe.

 

[twiz28]

A lot mention removing washer and snap ring from behind to bring secondary in. If this is enough to bring into range would you machine down plug same thickness? Or only machine plug when you machine clutch shaft?

 

[fatchance]

Only if you machine the secondary shaft

 

[fatchance]

I will add that you will most likely not get below 58mm offset until you have the shaft machined and this is only if your stub shaft bearing has not creeped inside the housing.

 

[JerryBones]

A lot mention removing washer and snap ring from behind to bring secondary in. If this is enough to bring into range would you machine down plug same thickness? Or only machine plug when you machine clutch shaft?

I can tell you from my experience, removing the washer and circlip, behind the secondary got me to 57.88 offset. and it made my belt deflection so tight that even after removing the two thin deflection washers my sled wouldn’t go into reverse because the belt deflection was still too tight. I would have had to machine the plug the same amount of the washer and circlip . I’m using an belt adjuster instead to set the deflection.

 

[DennyTuna]

Thanks to everyone with there input to this thread. I blew a belt on high speed run a couple weeks ago ( at about 100 mph) and it was violent and very loud, which I thought I blew the motor. The belt disintegrated into small pieces and I'm still trying to find them all. So this thread was perfect timing for me as I just knew my stub shaft most likely moved and it did, just over 1 mm. Did it right and used green bearing Loctite. Rechecked my offset and I'm going to shave 3 mm off the secondary. With the circlip in I'm at 60.3 so this will allow me to run my .5 mm washer against the circlip which should put me right at 57.8 mm. Really can't thank this forum enough. I know this my life membership has paid for itself many times over.

 

[Thunder Products]

Updated info from all these belt blowers.... weekend of 2/5/21 - 2/8/21

Belt blower #1 (2020 SW LTX studded track)
3 belts in 115miles. Nothing but heat from belt and clutches. Offset was 61.2mm with 1 shim. 300 TD tuned with Daltons.
After machining 3.5mm off of the back of the secondary, with 1mm shim and the circlip, the offset now was 58.7mm.
After numerous back to back runs, basically riding the sled like an a$$hole (owners own words), the belt showed a little "chipping" on the top cogs, one side only. But, no blown belts and this was 150-200 miles.
Took out the shim and butted up against the circlip, the dimension is 57.7mm and no issues. The owner is happy and has well over 500 miles on his belt as of last week.
**Update** This sled continues to blow belts. 2 more belts this past weekend. But now it's a clean break, not a bunch of pieces. Next is pull the clutches apart and go through everything.

Belt blower #2 (2017 SW RTX non-studded track)
3 blown belts on 1 ride, puppied the sled back to the trailer with an old Yamaha 8DN. Offset was 60.9mm. Precision EFI 280 tune and Thunder Products Clutching. Got a call saying he's dropping of the sled at my shop and wanted it just like Belt blower #1.
Machined 3mm off his secondary, offset is now 57.8mm and after a good weekend, no more belt issues.
**Update** Over 300 miles this weekend of beating the snot out of it and no issues what-so-ever!

Belt Blower #3 (2017 SW BTX with 153" 2.5 track)
Usually not a belt blower, but could blow a belt on command when full throttle. Offset was 59.9mm...no shim and against circlip.
TD tuned, with all the tunes including race tunes.
Machined 3mm off of the secondary and with a thin shim, the dimension is 57.8mm with 1 shim. No issues so far.
**Update** Over 230 miles this past weekend, lots of hard pulls and playing....no issues.

Belt blower #4 (2019 SW tuned with RCMP?)
Blew belts on command. Clutches always hot and not happy with clutching setup. Installed Thunder Products Clutching Big-V setup and did some offset checking, he is now "catwalking" his sled down fields he could never do before.
**Update** No Issues at all

New information from another belt blower from out east that we rebuilt his clutches, put in our kit and received this email from him this morning.
"Hey guys hope everything is going well, regarding my sidewinder....

Was opening it up today and on long hard pulls

The nytro clutch with your combo and redline belt have not blown a belt yet.

And believe me it would have if was still set up like last year. Oh my setup from you 280 precision efi evo muffler.....matt"


These are the results coming in from these belt blowers and just trying to get them so they don't blow belts anymore.

 

[Janne339]

And offset is affected by which belt you use? Longer or narrower belts should require less offset. A wider belt more offset?

So if you use the longer 8dn belt, I guess less offset is needed compared to 8jp?

 

[Thunder Products]

And offset is affected by which belt you use? Longer or narrower belts should require less offset. A wider belt more offset?

So if you use the longer 8dn belt, I guess less offset is needed compared to 8jp?

Offset was never really an issue back in the day, no matter what belt was used....but now it seems like 1mm is the difference between a belt blower and a non-belt blower in some cases.

Changing of belts seems to add to the variables.....

Thunder Products Clutching tries to stay with the stock 8JP belt (belt that the sled came with), or a direct equivalent which is the Gates 40R4313 new belt that is supposed to handle more stress/heat.

 

[TPAY243]

Thunder Products have you done any testing with the Utimax XS825 belt ? Not that it is a cure all but I have been having real good luck with it on my old turbo Viper and now on my Winder

 

[jonlafon1]

So belt blower #1 continues.. Different kind of break though.. That could be a clue! So IMO this kind of blow is not heat related, but more binding and or belt whip. So is #1 have float on the secondary? Knapp mentions the possibility of the secondary hanging outward on hard pull? If floating in secondary.
Possible binding >spring , roller. I know when I blew 2 belts in the first 500 miles I could almost do it at will.. Hard pull let off and back on it fairly quick. So the belt kind of hangs and has slack and BAM like a whip. Breaks fairly clean in one spot.. NOT into 500 pieces. M2C

 

[Sidewinder-X]

I thought removing the float in the secondary clutch was supposed to help?