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  #241  
Old 01-14-2020, 06:58 AM
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DanH DanH is offline
 
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Quote:
Originally Posted by rwtalbot View Post
How are you attaching the gear to the shaft? Loctite 638 might be an option with interference fit, or is there still room for a grub screw? There must be a secure solution involving a minimum of machining. It looks like Dan may have used grub screws.
No grub screws for me. Both the trigger wheel and the bearing collar are a light press fit locked with ASME B18.8.2 split pins in double shear, 0.125"D.

The idea was to create a cartridge, a complete shaft assembly for insertion into the body. It is retained with a surface plate, rather than the internal snap ring chosen by Colin. An internal ring requires installing the trigger wheel after the fact.







All dimensions are nominal. Detail all bearing fits. Trigger wheel is a KSS1-36 from from qtcgears.com.

Usual caution; experimental, use at your own risk.
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Last edited by DanH : 01-14-2020 at 07:03 AM.
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  #242  
Old 01-14-2020, 01:04 PM
WingsOnWheels WingsOnWheels is offline
 
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Quote:
Originally Posted by rwtalbot View Post
Interesting, so you have an O-ring seal at the top or is that grove for bearing retention?

How are you attaching the gear to the shaft? Loctite 638 might be an option with interference fit, or is there still room for a grub screw? There must be a secure solution involving a minimum of machining. It looks like Dan may have used grub screws.
The groove at the top of mine is for a snap ring to retain the bearing.

The spacer between the bearings is retained to the shaft by a dog-type grub screw. The tip of the screw has an unthreaded portion that fits into a matching hole on the shaft. The tip extends about 3/8' into the shaft and is 3/16 diameter of grade 12.9.

The top gear is held on in a similar fashion. However, since my gear position lined up perfectly with the existing rivet holes in the shaft (from where the magneto was cast on) that pin passes all the way through the shaft. There is also a regular grub-screw on the gear as well. I just left that since there was already a second threaded hole from the gear manufacturer, so why not. According to the spec for Grade 12.9, that little 3/16 dog should have a shear strength close to 19k pound.

In my case, the bottom bearing is pressed in. and everything else is assembled on top of that.
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Last edited by WingsOnWheels : 01-14-2020 at 01:07 PM.
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  #243  
Old 01-14-2020, 04:16 PM
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Had a private note with a very good suggestion. The trigger body could have an oil weep hole to vent the bearing space. It would offer an early indication of oil seal failure. Although oil is unlikely to bother the magnetic pickup, oil washing is not good thing for sealed bearings.
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  #244  
Old 01-15-2020, 05:56 PM
WingsOnWheels WingsOnWheels is offline
 
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I have one, wasn't planned for that purpose. It is and access point for the dog in the center bearing spacer, just in case. At least I was smart enough to align it with the timing, so I can stick an allen wrench in there snd it will hold the gear properly aligned with the pickup.
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  #245  
Old 01-23-2020, 06:25 PM
rwtalbot rwtalbot is offline
 
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Default Detailing Bearings

Quote:
Originally Posted by DanH View Post
No grub screws for me. Both the trigger wheel and the bearing collar are a light press fit locked with ASME B18.8.2 split pins in double shear, 0.125"D.

The idea was to create a cartridge, a complete shaft assembly for insertion into the body. It is retained with a surface plate, rather than the internal snap ring chosen by Colin. An internal ring requires installing the trigger wheel after the fact.
Thanks for the updated diagram Dan. I'm wondering what your thoughts on detailing the bearings are? Figuring to reverse engineers something with some service history, I measured 0.002" interference fit on the outer race of a slick core (6002 40mm OD Bearing). Given the relative expansion rate of the aluminium housing, vibration and estimated operating temperature of ~100C that seems like a reasonable number to shoot for on the outer races.

One of the other vendors appears to use Loctite retaining compound to hold the bearings in their housings however I think that is pushing the friendship with an aluminium housing exposed to the heat of the engine bay.

The shaft measures 0.0003" over the inner race which would put it towards the tighter end of a js5 fit etc.

Regards
Richard
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  #246  
Old 01-23-2020, 06:27 PM
rwtalbot rwtalbot is offline
 
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Quote:
Originally Posted by DanH View Post
Had a private note with a very good suggestion. The trigger body could have an oil weep hole to vent the bearing space. It would offer an early indication of oil seal failure. Although oil is unlikely to bother the magnetic pickup, oil washing is not good thing for sealed bearings.
This is a good idea. It is also possible that the unit could be exposed to water from an enthusiastic degreasing. It is always best to allow the fluids out. I have seen electronic circuit boards corroded by sitting in water in similar circumstances.
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  #247  
Old 01-23-2020, 07:32 PM
lr172 lr172 is offline
 
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Quote:
Originally Posted by rwtalbot View Post
Thanks for the updated diagram Dan. I'm wondering what your thoughts on detailing the bearings are? Figuring to reverse engineers something with some service history, I measured 0.002" interference fit on the outer race of a slick core (6002 40mm OD Bearing). Given the relative expansion rate of the aluminium housing, vibration and estimated operating temperature of ~100C that seems like a reasonable number to shoot for on the outer races.

One of the other vendors appears to use Loctite retaining compound to hold the bearings in their housings however I think that is pushing the friendship with an aluminium housing exposed to the heat of the engine bay.

The shaft measures 0.0003" over the inner race which would put it towards the tighter end of a js5 fit etc.

Regards
Richard
Do your research here. Bearings in these applications typically have one interference fit and the other with slip fit. I built a similar device and used interference on the shaft and .001 slip on the outer shell (recommendation from bearing company driven source gets interference). I did use wave washers on the bearing retainer to add a bit of tension on the bearing to prevent any spinning. Also a recommendation from the bearing engineers. Every alternator or similar device that I took apart was done the same; one interference and one slip. which one varies with application.

I am told that two interference fits will take too much clearance from the ball/race interface and is a problem for high RPM applications.

Larry
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Last edited by lr172 : 01-23-2020 at 09:18 PM.
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  #248  
Old 01-23-2020, 08:12 PM
rwtalbot rwtalbot is offline
 
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Quote:
Originally Posted by lr172 View Post
Do your research here. Bearings in these applications typically have one interference fit and the other with slip fit. I built a similar device and used interference on the shaft and .001 slip on the outer shell (recommendation from bearing company driven source gets interference). I did use wave washers on the bearing retainer to add a bit of tension on the bearing to prevent any spinning. Also a recommendation from the bearing engineers. Every alternator or similar device that I took apart was done the same.

I am told that two interference fits will take too much clearance from the ball/race interface and is a problem for high RPM applications.

Larry
The data I have here indicates that at 100C you can expect the deviation of clearance/interference of .0018" on a 40mm bearing bore. To me that indicates why the Slick is bored 0.002 under as once up to temperature the fits are correct. I am making an assumption here that the Slick bearings generally run to TBO without failure.

The following document makes mention of previous problems with Champion magnetos caused by loose fitting bearings, severe side loadings and/or high temperature (page 6).

https://www.casa.gov.au/sites/defaul...files_redirect.
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Last edited by rwtalbot : 01-23-2020 at 08:18 PM.
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  #249  
Old 01-23-2020, 09:13 PM
lr172 lr172 is offline
 
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Quote:
Originally Posted by rwtalbot View Post
The data I have here indicates that at 100C you can expect the deviation of clearance/interference of .0018" on a 40mm bearing bore. To me that indicates why the Slick is bored 0.002 under as once up to temperature the fits are correct. I am making an assumption here that the Slick bearings generally run to TBO without failure.

The following document makes mention of previous problems with Champion magnetos caused by loose fitting bearings, severe side loadings and/or high temperature (page 6).

https://www.casa.gov.au/sites/defaul...files_redirect.
Does slick use and interference fit on the shaft AND the bearing housing bore? My point was not the amount of interference, but that the bearing ID should be interference and the OD slip.

My intent was not to question your effort here, only to point out what I learned from engineers that do bearing application engineering for a living.
Larry
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  #250  
Old 01-23-2020, 09:19 PM
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DanH DanH is offline
 
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Originally Posted by rwtalbot View Post
I'm wondering what your thoughts on detailing the bearings are?
Seriously, I built those things four years ago, and don't remember exactly what I did. I think you have a handle on it.
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