Helhedded's Comp Shafty

[Szczerba]

Originally Posted by helhedded

Well then.

Holmes Hobbies sells knives now? Motor specs?

[winnerone23]

X2.. I'm with Shane!

[helhedded]

There are some specs on page 15, however something has changed since then due to the weight being different. I kinda let John do what he wanted with this one. Maybe he'll chime in with a laundry list of fancy tech stuff.

[winnerone23]

Originally Posted by JohnRobHolmes

Ashton contacted me about a custom motor for his shafty build, and decided to take a little gamble and let me design something out side of the box for him. His requirements were bigger power than a regular 540, but he also wanted to have lower weight. Size was not a concern. To start the build I pulled the design files from the original Puller 520 Stubby and converted them to a brushed configuration, since that is what he wanted. We start with a known Flux Gap Area (FGA) to accurately predict the power and torque from any given motor, otherwise we would just be stabbing randomly at rotor sizes. The FGA we start with on this motor is 1,588 square millimeters.


With a full 36mm of diameter to work with, we have a lot of room for a rotor when using Neodymium magnets. A 28mm rotor easily fits, with plenty of space for airgap and properly sized magnets to prevent tooth saturation. Working backwards from the FGA we get a rotor length of about 18mm. I just happen to have a tray full of 1588FGA 28mm rotors here


The next step is to determine magnet thickness, airgap, and back iron thickness to ensure that oversaturation does not occur. I use FEMM for this, a CAD type software for magnetic and thermal modelling. Because of the tooth profile and two magnetic pole design, 33EH Neo magnets were selected. Going stronger doesn't gain performance, and it reduces the operating temp of the motor while increasing cost. A different rotor or magnetic layout would be needed, and has been designed for future research.


All processes and machining were done by me on my equipment.


Here is the finished rotor, it is just a shade shorter than a regular 540 from bushing to bushing, but a bit heavier. Because of the large diameter, we have better leverage than a regular 540. Puller 520 on the right, regular 540 on the left.





The can was machined from an extruded housing. It reduces cost as compared to a fully machined design, and offers better rigidity than billet material because of work hardening during the extrusion process. A flux ring was integrated into the can design to ensure highest torque. For a few gram penalty we get an 8% reduction in motor speed, thus 8% lower resistance. Resistance robs power more than a few grams, so the consideration was a no brainer. Future revisions could save a few grams with an alloy faceplate, it will be tested and compared on a cost/ benefit analysis. Shown in the raw-






The motor is held together with retaining screws that run the length of the motor. I have been searching for over a year for a screw maker that could make the particular size I needed, with zero luck. Not a single factory had the tooling I needed, and spending 10 grand for a single screw size is foolish for even a rich man. So I made them myself with my spoke machine and some custom extruded spokes. It removes a few grams from the motor, reduces parts count, reduces labor of construction, and reduces cost almost $10 vs alloy screws and a timing ring. Win, Win, Win! The fine pitch grabs very well into plastic, just 2mm of thread engagement locks it down.





Final Specs:
5 slot 28mm diameter rotor, precision polished and dyed
13t Double wire for highest fill
High tempurature silver commutator termination
200c epoxy VOI impregnated coils
Dynamically balanced with the finest German Epoxy
Diamond trued Commutator

Steel can with Integrated Flux ring
EH33 Magnets, 200c rated
200c industrial epoxy
ABEC 7 bearings

Team Endbell
Holmes Silver Standup brushes
Holmes X springs
Holmes lightweight spring posts

Weight, 5.1 ounces
36mm diameter, 52mm length

Next I will bead blast and apply a special Ceramic low friction coating, then we will reweigh it. As compared to a regular 540 of the same speed, the Puller 520 has 38% lower terminal resistance and is 28% lighter. All in all, this motor will do the job nicely for Ashton. Have your cake and eat it too!



Next on my agenda, a Puller 510 Stumpy to increase terminal resistance to equal that of a 540.

Sweet read! Ready for a run down when ya hit the rocks with it..

[JohnRobHolmes]

Changed back to a timing ring setup for simplicity, otherwise basically the same specs as were stated.

[Szczerba]

Guess I missed the part on the spoke modified pass though screws. Awesome.

[Hittman]

Awesome. I am still loving mine in my xr.

[rofo]

What in the approximate kv on that 13T Puller?

[JohnRobHolmes]

I'm not totally positive, my tach went kaput right when we were doing final assembly on them. If my memory serves correctly it was about 2000 to 2100kv.

In production models, it is the Puller 520 Stubby. We don't use as much wire as Ashton's since the average shafty doesn't have a big enough battery to handle such a low terminal resistance.

[rofo]

Originally Posted by JohnRobHolmes

I'm not totally positive, my tach went kaput right when we were doing final assembly on them. If my memory serves correctly it was about 2000 to 2100kv.

In production models, it is the Puller 520 Stubby. We don't use as much wire as Ashton's since the average shafty doesn't have a big enough battery to handle such a low terminal resistance.

OK. Thanks for the info.

[JohnRobHolmes]

You betcha. 13t and 16t have gotten great reviews from drivers that have them. We have a few more available now.

Holmes Hobbies LLC- Puller 520 Stubby

[helhedded]

...



something funky was happening with the editor and just to show some love to my sponsors and two mega-awesome websites



Current specs:

Holmes Hobbies 520 Stubby (13T)
RcBro 600 mAh 3s 30c Lipo
14t motor pinion
90t/48p spur gear
36/14 front axle gearing
43/13 rear axle gearing
RTR weight: 4lbs, 4 ounces (1 ounce less than before the recent modifications)

[Szczerba]

Sweet. Looks like we are going to have to start building courses with 1 minute time limits.

[TURBOFEST]

Whoa!

[helhedded]

540 vs. 520 size comparison



After beating on these Junfac shafts for over a year they are still in great shape. The HD heat shrink works and has held up well, but I think it's unnecessary.



Still, why the eff not



...did a little drilling on my outputs. The one on the right is nasty... lefty was with fresh bits. Doh! Overall they lost somewhere around 7 grams. These are the older steel Crawler Innovations outputs.



It's not as light as others, but I'm happy with it.

[Erik D_lux]

Awesome vid! Lol

[Duuuuuuuude]

Originally Posted by Szczerba

Sweet. Looks like we are going to have to start building courses with 1 minute time limits.

And kicker ramps.





And maybe a half pipe.




Time bonuses for clean backflips as well?

[banners]

Am I missing something here? Crawlers - go slow? lmao!!! Rig looks like it's got a rocket up it, top banana!

[winnerone23]

What's ur gear ratio, by chance?

[helhedded]

Originally Posted by winnerone23

What's ur gear ratio, by chance?

14/90 and according to this Axial tips and tricks it's 49.45