Dan, do you recall how you measure current?
Average, just a Fluke multimeter in series.
I?m guessing my setup is showing peak current snapshots.
Me too, but I have not put a scope on it.
Dan, do you recall how you measure current?
I?m guessing my setup is showing peak current snapshots.
Sure. This would be the 4-cyl orientation, slip-over-hub style... [snipped]
Average, just a Fluke multimeter in series.
Me too, but I have not put a scope on it.
Stepping a back a number of pages to the topic of run-up testing of the electronic ignition system. Rather than shutting off power to the electronic system and relying on a smooth return to timing. What about grounding the primary coil (just like a mag), but through a resistor to eliminate a current spike. That way the timing circuit is still active and you simply dissipate the spark energy. It should be a smooth transition then.
Dan, all good feedback. The spacer is a shaft collar, so it does retain the shaft.
Yes, the gear will have to be removed in order to remove the snap ring, but that shouldn't be a problem. The shaft has two existing holes from where the magnet was attached, I'm hopeful those will line up close enough to be used for the gear retention, but I missed one critical dimension when I pulled my mag to measure, so I don't know for sure yet.
Dan,
Do you happen to know either:
The distance from the shaft shoulder to the face of the mag drive gear, or the distance from the magneto-to-acc housing face to the shaft shoulder? I failed to get that measurement when I pulled my mag.
Not sure of what your mean by "shaft shoulder". Got a drawing for dummies?
The shoulder where the shaft taper transitions to the threaded portion for the mag drive gear. Basically I need to figure out the position of the mag drive gear on the shaft.
The sholder where the shaft taper transitions to the threaded portion for the mag drive gear. Basically I need to figure out the position of the mag drive gear on the shaft. Hoping to do so without pulling the mag again, but that may be what I have to do.
Dan, What wire gauge did you use for the coil pack?
...pickup assembly is all together and ready to roll.
Thanks guys. Great information.
I'm thinking at this point I will probably just get an 8 cylinder plug new from your side of the pond (half the price of UK) and cut the keys of it as Kirk suggested.
Be nice to have one that has NOT been pre wired like this one or a source for replacement female pins perhaps? Any Ideas?
I'm too lazy to go thru the thread but I would like to make a couple of these on my CNC turret lathe. Can someone point me to a non-metric drawing or a Solidworks file?
How do you remove the magnet/rotor assembly from the shaft? Is it a press fit?
Thanks
Richard
Where are you guys mounting your coils? In the upper plenum area would make for short plug wires (for one set), plus it is pretty cool during flight. On the other hand, on the firewall gets them away from the vibration.
On the 6, I put the coil on the firewall. Not enough room to put on top of the engine with the coil type I had (top facing posts). On the 10, I put one on top of the engine and the other on top of the engine mount. The 10 cowl area has a lot more room to work with though.
Larry
The one i used was from a slick mag. I tried to machine it off with poor results. Then i realized it is cast on (maybe aluminum) with the magnets embedded in the casting. I ended up just melting it off with a propane torch. Then there were two brass rivets that I drilled out.
Thanks Colin, I had issues with the first one too. On the second one I found an angle grinder removed most of it. I then carefully removed the remainder with the lathe.
I'm happy to repost my drawing in inches. However, my setup is yet untested. Also, I made a few minor tweaks that aren't on the drawing. I made the o-ring grooves slightly deeper and made the engine-side bearing press fit and the aft bearing slip-fit.
Yes that would be great.
Would like a drawing of the shaft as well. I think it would be ok to make it out of 4140 or 8620 steel.
Bob,
Sorry for the delay. Here is my housing drawing in inches.
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.
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.
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.
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.
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.
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/default/files/_assets/main/airworth/awb/74/005.pdf?acsf_files_redirect.
I'm wondering what your thoughts on detailing the bearings are?