26D 'Monster Mash'...
#1
Posted 23 October 2018 - 12:59 AM
Going to add a few little twists into the mix such as fiberglass thread instead of Kevlar, liquid brazing flux and single component system epoxy. Have to wind with #25 wire because it's all I got at the moment.
Not sure where all these parts are going yet but we are surely gonna find out.
This should help calm me down some, I'm sure...
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Yes, to be sure, this is it...
#2
Posted 23 October 2018 - 01:46 AM
26Ds are cool.
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Steve King
#3
Posted 23 October 2018 - 06:50 AM
Looks like a bunch of nifty parts you have assembled there Geary! Besides the Arcos/shim, I see an FC280 can and magnets...mmmm, tastey. If you can manage a workable "hole", the FC280 magnets will be a better match for such a stout wind as a #25, but I'm sure you have a plan. Build-on!
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#4
Posted 23 October 2018 - 03:14 PM
If a #25 calms you down, what are you normaly running? Watching with interest.
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#5
Posted 23 October 2018 - 10:31 PM
If a #25 calms you down, what are you normally running? Watching with interest.
At the moment not much...
Yes, to be sure, this is it...
#7
Posted 29 October 2018 - 01:18 AM
Looks like a fair bit of timing on there.
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Steve King
#8
Posted 30 October 2018 - 06:07 AM
Looks like a FINE job to me Geary. Rock-on man!
Looks like a fair bit of timing on there.
Judging by the top picture, which is of course difficult, timing looks to be 15 degrees or less, which would be appropriate if so.
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#9
Posted 06 November 2018 - 12:24 AM
.051 ohms per pole. Timing 25 degrees + or -.
The only way to get the coils to wind properly was to jam 7 turns on the first layer and then stack some wood. Any backing turns that I tried just made a mess.
Had problems getting the silver braze to flow properly with the "loopy" comm tabs. Turns out the copper alligator clip that I normally use for the ground connection on the comm was not conducting enough heat into the comm. Switched to a high resistance nickel plated steel alligator clip and the problem was no more.
Next up is the fiberglass and then epoxy on the spit.
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Yes, to be sure, this is it...
#11
Posted 08 November 2018 - 06:36 AM
Looks great Geary. Fiberglass works fine, and is obviously as "heat-resistant" as possible...basically flame/fireproof. Those long end strands aren't helpful to a spinning arm's "aerodynamics", but they can sometimes be cut-back after the epoxy cures if they're not actually bonded to the tops of the coils. One good thing about fiberglass is that it's excellent at "wicking" epoxy and getting fully saturated.
Believe it or not, unwaxed dental floss works well too. While not nearly as heat tolerant as fiberglass or kevlar thread, it's probably good to 300F which is about where other things can start to fail anyway (*depending on a bunch of other variables).
You made an awfully pretty arm, fine work!
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#12
Posted 08 November 2018 - 11:10 AM
Thanks John,
I didn't realized how much fun working with fiberglass thread would be.
It wraps nicely but trying to get a knot to stay knotted is a bit much, that is why the whiskers were left, to be broken off after the fact.
- havlicek likes this
Yes, to be sure, this is it...
#13
Posted 09 November 2018 - 12:46 AM
Epoxy and glass are cooked and cooked some more.
Cure schedule for single component system epoxy is a bit much but here it is:
120C/3 hrs.
165C/6 hrs.
185C/1 hrs.
I would say that this epoxy is cross linked.
Here is the spit that did the deed.
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Yes, to be sure, this is it...
#14
Posted 09 November 2018 - 06:26 AM
At 10 hours of oven time, the electric bill alone here would send shudders down the spines of the Congressional Budget Committee Looks mighty tastey!
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#15
Posted 09 November 2018 - 02:10 PM
I like your oven rotisery.
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#16
Posted 09 November 2018 - 08:35 PM
Nice arm, Geary, you are a good cook
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Paul Wolcott
#17
Posted 09 November 2018 - 11:29 PM
Thanks guys...
Yes, to be sure, this is it...
#18
Posted 23 November 2018 - 06:09 PM
Soldered the can bearing in backwards for extra arm spacing inside the can because I'm using the full length Mabuchi 280 magnets. Cut the 280 can down to use as a shim inside the 26D can and wound up with a .592" hole. Arm OD will be ground to .580" for a snug fit.
Ruminated about the ole C can hi temp end bell but went with a more vintage approach, sort of.
Maybe 36D brush holders and hoods?
Decided that it was living a tad dangerously with 23/25 so I tried this...
The Acetal end bell has a bit more chance of survival. Buss bars fit nicely but did a more compact setup.
Thermal management can be taken further but will be for another motor...
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Yes, to be sure, this is it...
#19
Posted 23 November 2018 - 06:51 PM
6 thou per side airgap? Holy cow, that's tight
I love it, looks like it will be a rocket
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Paul Wolcott
#20
Posted 23 November 2018 - 08:32 PM
yeah, I've had to put the bearings in backwards as well. good thinking.
but that's the cleanest thing that I think I've ever seen! good on ya.
.006 is a little tight. be interesting to see how it does. will you be honing it?
speedy .
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#21
Posted 23 November 2018 - 11:29 PM
6 thou per side airgap? Holy cow, that's tight
I love it, looks like it will be a rocket
Thanks Pablo, a bit tight but have used this approximate spacing before with these Mabuchi mags, we will see how it all comes together.
Yes, to be sure, this is it...
#22
Posted 23 November 2018 - 11:41 PM
My comment isn't performance related; it's just that I worry if there is the slightest bit of misalignment there is no fudge factor.
Perhaps due to a wall shot, or the imprecise nature of 45 year old parts (despite your ultra-high level of assembly precision).
From a performance standpoint, ain't nuttin wrong with it and I know you know that
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Paul Wolcott
#23
Posted 23 November 2018 - 11:59 PM
yeah, I've had to put the bearings in backwards as well. good thinking.
but that's the cleanest thing that I think I've ever seen! good on ya.
.006 is a little tight. be interesting to see how it does. will you be honing it?
speedy .
Thanks Steve,
Soldered the bearing from inside the can after using the bearing coated with valve lapping compound to remove the chrome on both sides of the can.
I'm not going to hone the mags. The 6 mil clearance is at the smallest distance, between the center of the elliptical magnet faces, while the tips of the mags are another 8 or so mils additional clearance.
Yes, to be sure, this is it...
#24
Posted 24 November 2018 - 12:20 AM
My comment isn't performance related; it's just that I worry if there is the slightest bit of misalignment there is no fudge factor.
Perhaps due to a wall shot, or the imprecise nature of 45 year old parts (despite your ultra-high level of assembly precision).
From a performance standpoint, ain't nuttin wrong with it and I know you know that
For this tight a gap I will use mylar shims on both sides of the arm assembled in the can with magnets and end bell as the epoxy between the can and mags cures. This keeps everything aligned quite nicely. I also leave the mag springs in place as extra insurance.
Yes, to be sure, this is it...
#25
Posted 24 November 2018 - 09:02 AM
nice. I've also used shims if needed so that the magnets were set the same top and bottom in the can. the techniques I learned with C-cans, etc. flowed up to cobalts (where everything has to be perfect!) and then back down. I know that there are far better motor builders out there than I, but I did get pretty decent at 'em. once I figured out what I needed, I used to machine my own slugs and can tools and make my own alignment fixtures because I got tired of having a million tiny flidgets all trying to escape.
back in the day, we used to cut out magnet shims from Tang jar lids!
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