Sunday, October 17, 2010

Moar Bord

So by popular demand, the project is renamed "HÄRDBÖRD". I second this change because I did not much like calling it Fluffy, being not fluffy but still incredibly adorable. All previous references to Fluffy former will be updated to HÄRDBÖRD. I need a better way to inserting Umlauts into text...

Onto the interesting
stuff:
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Had another massive build session last night at the Inv
ention Studio. This one pretty much wrapped up the mechanical aspects of the board. Safe to say, it is drivable by method of kick.

Last build session I had the board almost drivable e
xcept for the turnigymotors which were plain can. Yeah, not going to rough up that beautiful Chinese machining for some unenjoyable joyriding. So first operation of the evening was coring out some wheels.


Here is the invention studio baby-lathe in the back corner of the o
ther room. A bunch of really cool automated machines sit here, but only 4 of them belong to us (CNC not included). Still this lathe is pretty sweet, because it can do the whole threading trick. Other than the standard lathe functions (gear ratios, digital readout, etc.) it has an auto jog. Woot.

Mounting the wheel to the chuck was an interesting task because the jaws were not exactly large enough to handle the object. I had to resort to the inner set of teeth
and crank really hard into the soft 30A durometer wheel tread... Sounds like a terrible idea.



But it came out pretty awesome. Wheel, cored ring-o-wheel, motor can, and motor core all in one picture. A perfect slide-press fit too (with the exception of the screw he
ads)!


Partway through, I realized we would have to push an extra .25" deep so we could access the screw heads on the near side bearing of the motor. For this, we employed a rando
m piece of scrap. And Arrrrrrborrrrrrrrr presssssss.

Bam, wheelmotor...and then there were two.



Two motors one truck?

Then reassembl'd.


While Xo assembled his stuff, I made a few laps around the MRDC on the board. Verdict: it works but with corrections that need to be addressed.

The springs are too soft. While the truck turning geometry is fin
e, the springs used to give resistance to the turns are too soft which makes the board very... "responsive". It is far too easy to over turn and drive some retarded sinusoidal board path. This probably means some design correction is in store. When I say probably, I mean definitely.

A very important but final modification to this build session was the shortening of the power pack. The stock 4Ah, 6s1p lithium batteries I purchased were 39mm tall (~1.5" +4mm) which is taller than I would have liked it. The goals for this now are to fit everything underneath the 1" square 8020 piece, which might be just impossible depending on how tall the out pins on the Maxons are. Eitherway, introducing longpack.


..and oh yes, it is very long. (163 x 2)mm long, which is over 1 foot of POWER.

IT IS A 4 AMP FOOTLONG!!!



11 comments:

  1. Are you implying that longpack is long? Your project is looking awesome Jamison, can't wait to see it up and running.
    -Skyler

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  2. lol oh yes, it is quite long. Thanks man, I'll keep ya posted!

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  3. Nice project guys. Clever instant hub-motors. I've been working on something similar for the past year. Check it out:

    http://mitrocketscience.blogspot.com/search/label/ELB

    -Jed

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  4. Sweet Jed! Actually funny story, I ran into your work a long time ago, I think about the time you were turning the endcaps for the motors (which I totally dig BTW).

    I can't wait to see yours rolling! 4-wheel drive FTW

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  5. Your board looks really sweet. Needless to say I wants. I finally got around to pursuing this same project on my own and I'm at a stage of spec'ing a good size motor. I reallly like the simplicity of your hub motors and they're the perfect size for sure (physically) but I can't justify to myself that you'll get enough power at the ground (namely in the form of torque). What do expect for torque with these stock? websites don't have any good datasheets...

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  6. That is a very good point Matt. I have similar concerns in the design, mainly concerning current draw and capacity of the batteries. My current plan is the rewind the motors to a kv ~50rpms (as opposed to ~280rpms). This should increase "torque" and battery life. I say "torque" because sensorless brushless motors don't really "have" any. The end all solution (which will be implemented) is the addition of hall effect sensors for motor can positioning. This will let the esc know which phases of winds to power, which should give the motor something comparable to torque.

    So really, I don't expect anything in the way of torque, but there is no sense in ripping out the windings yet; might as well have some fun since they are prewound :P.

    As an additional note, I ran the longboard the other day (powering one motor) via my dx6i, an 60A sensorless controller, and a 11.1v lipoly the other day and It could move me (violently quick) with a little push start. I should put that video online... haha

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  7. That's promising. I'm definitely hoping to give this a shot. Also on my infinite list of things to do is put up a blog so I can join this party online officially...

    and you should put up that video. the more sparks/smoke/cursing/falling the better.

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  8. are these bearings the original with the motor?

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    Replies
    1. The bearings found in the hubmotor are the stock bearings with the turnigys. However, the thrust bearing was purchased from McMaster-Carr.

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  9. Are the motor really strong to support all the weigth as a Hub Motors?
    Do you finish the project there is any video or something

    ReplyDelete