Astral Rune build thread

Discussions related to motors other than hub motors.
This includes R/C motors, botttom bracket, roller and geared drives.
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ferret   1 kW

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Astral Rune build thread

Post by ferret » Aug 14 2016 8:52am

Hi everyone.
This thread will document my new project. I will post photos and description of the process, feel free to ask if you want more details.

This build is based on a Banshee Rune V2 frame. This is the only frame I could find that ticks the following boxes:
* Modern high quality mountain bike with at least 160mm travel.
*BB width 73mm (or less).
*Rear dropouts width of 150mm (or more).

Bare frame:
20150716_184543.jpg
20150716_184543.jpg (245.11 KiB) Viewed 1889 times
The first stage of the project was building up the bike (human powered).
Complete bike:
20160125_203633_HDR.jpg
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ferret   1 kW

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Re: Astral Rune build thread

Post by ferret » Aug 14 2016 9:18am

Now the electric conversion can begin.

Chainring:
I used a Cyclone 73mm ISIS BB. Since I'm using it with standard ISIS cranks (with no freewheel), I need to turn some chainring spacers to get the correct chainline.

Spacers and assembled chainring:
20160128_203619_HDR.jpg
20160128_203619_HDR.jpg (179.39 KiB) Viewed 1901 times
20160128_221412_HDR.jpg
Rear wheel:
I had a "Tophat" adapter made that mounts a 130mm BCD chainring to the rear hubs brake disk flange:
20160627_102842_HDR.jpg
The 150mm rear spacing allows room for both sprocket and a standard brake caliper, although a custom caliper adapter is required.
20160627_194414_HDR.jpg
View from back:
20160701_210536.jpg
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ferret   1 kW

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Re: Astral Rune build thread

Post by ferret » Aug 14 2016 9:38am

Motor and motor mount:

As you might have guessed, the motor chosen for the build is an Astroflight (3215 7T). Plates are used to mount it to the frame. They allow the motor to be moved for chain tensioning and they clamp it from both the front and the rear for effective heat removal.
Attachments
20160630_233324.jpg
20160630_233430.jpg
20160630_233348.jpg
20160630_214415.jpg
20160702_165906.jpg
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ferret   1 kW

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Re: Astral Rune build thread

Post by ferret » Aug 14 2016 10:13am

Reduction:
The build uses a 2 stage reduction. A #25 chain connects the motor to to the "jackshaft" and a single speed chain connects the "jackshaft" to the rear wheel. The"jackshaft" contain a left hand freewheel and is floating on the BB spindle.
Attachments
20160814_174749_HDR.jpg
20160814_174859_HDR.jpg
20160814_175049_HDR.jpg
20160814_175316.jpg
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Re: Astral Rune build thread

Post by ferret » Aug 14 2016 10:23am

Chain management:

To compensate for the full suspension's chain growth I had to use a spring loaded tensioner. An additional pully is used to prevent the suspension interfering with the chain as well as to increase chain wrap around the small sprocket.
Attachments
20160809_194421.jpg
20160524_192156.jpg
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Re: Astral Rune build thread

Post by recumpence » Aug 14 2016 11:02am

Hmm, that adapter looks familiar. :wink:

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Re: Astral Rune build thread

Post by ferret » Sep 05 2016 9:51am

Everything seems ok on the stand.



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Re: Astral Rune build thread

Post by ferret » Oct 05 2017 4:46am

A few updates over the last year:
IMG_20171005_120936_HDR.jpg
3D printed chain cover:
IMG_20171005_120945_HDR.jpg
Chain tensioner made from a Simano clutch derailluer.
IMG_20170423_222026.jpg
Replaced Castle controller with a Phase Runner
IMG_20171005_120850_HDR.jpg
IMG_20170506_130122.jpg
Converted Astro motor to sensored operation
IMG_20170506_130136.jpg
Switching to sensored motor and controller made a huge difference when riding slow technical terrain.

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Re: Astral Rune build thread

Post by whereswally606 » Oct 06 2017 8:01am

Hey Ferret,
Stunning build, a lot of features that are superbly thought out. I like the top hat style adapter for the rear sprocket and brake, the LHS jackshaft on the isis BB. Also, that's a nice touch using one of burtie's opto boards on a grin phaserunner. Its a great choice of frame too, thanks for sharing the build.
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Re: Astral Rune build thread

Post by ferret » Oct 06 2017 9:52am

Thanks,
it took more than two year, but it's finally coming together. Slowly but surly :)

The Phaserunner made using Burtie's sensor PCB really easy to install. I simply glued it at a position where the wires will be shortest and the Phaserunner automatically detected the sensor angle relative to the winding. In most controller I would have had to find the angle the controller expects by a lengthy trial and error process.

Back when I started, it was hard to find a modern frame with "narrow" BB and "wide" rear hub spacing. Since then, Boost 148mm rear hub spacing became common so there are many other suitable frames.


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Re: Astral Rune build thread

Post by DanGT86 » Oct 06 2017 11:55am

Nice work! Did you have to turn down the bottom bracket spindle?

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Re: Astral Rune build thread

Post by flat tire » Oct 06 2017 12:58pm

That's a nice build. Where will the batteries go??

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Re: Astral Rune build thread

Post by ferret » Oct 06 2017 1:45pm

I did turn down part of the spindle by a few hundredth of a millimeter.
The bearings I used for the freewheel adapter have the same dimensions as the BB bearings, which are pressed on the spindle. I wanted to be able to install and remove the freewheel adapter without using a puller or high temperature, so I reduced the diameter of the part of the spindle where the adapter is located so it would easily slide on and off.

The batteries (2x6s 12Ah Multistar Lipos) go in a backpack.
One of the reasons is to reduce the mass of the bike and allow it to handle as close to a human powered mountain bike as possible. The bike weights 20.5 kg and does not feel as nimble as my non electric mountain bike.
The second reason is that I used a battery box on my previous build and the batteries became deformed/squished, probably as a result of harsh landing from drops and jumps. I guess a ton of padding could have prevented that but it would have been very cumbersome.

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Re: Astral Rune build thread

Post by bh4801 » Oct 06 2017 2:36pm

Nice work!
I like how cleverly you attach to existing frame features, the freewheel spinning on crank spindle, the motor mounted to pivots.
I am curious as to your motor selection, it would seem the overall ratio is ca. 24, with 27.5 wheels, 145 Kv motor and 45V average battery your top speed should be ca. 35km/h.
I would have thought at 45V * 145 Kv = ~ 6300 rpm you are only taking advantage of 1/2 of the rpm band, and therefore 1/2 of the power band of the 3215?
Why not a lighter & cheaper 3210-5 ?
Is that correct? Is this how you planned it?

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Re: Astral Rune build thread

Post by ferret » Oct 06 2017 4:13pm

You are pretty much spot on with your calculations.

I mostly ride singletracks so I'm not too concerned with "powered" top speed. I reach my highest speeds using gravity by letting off the brakes going downhill without touching the throttle.

With the Castle controller on 12S "hot off the charger", the motor should reach about 7300 RPM. I check the rpm at "hot off the charger" voltage because I want to make sure not to exceed the rated rpm and explode the rotor. The motor is rated to 10000, I can get there by either adding cells or using the Phaserunner's field weakening feature. By raising the RPM (and/or by changing the reduction ratio) I could get higher top speed, but right now I don't feel the need.

Deciding on a motor frame size between 3205 and 3200 involves trying to guess how to trade off between cost and weight vs power potential and heat soak resistance. Fortunately didn't have to agonize over it. I had one constraint that forced my decision; the sensor PCB could only fit the 3215 (without extensive modifications).

I guess what I wanted is a "mountain bike on steroids" that will allow me to climb steep technical singletrails and be an alternative to shuttles and chailifts that take you to the top of mountains (which are practically non existent here). That is quite different from the commuters, cargo bikes, fast roads and fast trail bikes that many of the forum members are building. The is why my build has relatively uncommon features such as sensored Astro motor, low power direct drive with a rear disk brake and a small capacity battery in a backpack.

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Re: Astral Rune build thread

Post by flat tire » Oct 06 2017 4:43pm

ferret wrote: The batteries (2x6s 12Ah Multistar Lipos) go in a backpack.
Terrible idea considering you should be standing most of the time. Put them on the frame, it will be much better.

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Re: Astral Rune build thread

Post by ferret » Oct 06 2017 5:13pm

As I mentioned, I already tried both frame mounted battery and backpack mounted battery and prefer the latter.
Not trying to convince you or anyone, especially not knowing your riding style, I feel that a backpack is better for me for the following reasons:

* More nimble handling.
* Less impacts to the battery because in is suspended by the arms and legs.
* Battery weight is dynamic, moving with my body instead of being fixed to the frame.
* Easily replace battery with one of a different size or carry multiple batteries (without building a different battery box).
* Easily charge battery off the bike.
* In case of Lipo fire, backpack can be quickly ditched and won't burn down the bike.

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