Dave's 80:1 RC mid drive kit build log

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Re: Dave's 80:1 RC mid drive kit build log

Post by 12-C » Dec 24, 2017 4:25 pm

Nice work Dave!

So the idea with the 2nd gen is that it will house more lubricant and be contained? Personally I really don't mind the shoot .5ml in the motor at your regular maintenance-idea. If it wasn't for that I'm sure I'd be skipping my necessary chain maint.... that's just how it goes for me lol.

What spurred you to change things up with the design?
Were you trying to eliminate steps/streamline machining and assembly/reduce number of components? Or were you having concerns about longevity of the 1st gen? I've had nothing but fun on mine.

The idea for a bolted side plate is just a thought. I'd prefer not to have to undo-redo the threaded portion of the BB, it seems like one of those components that isn't really meant to be on/off cycled. Those delicate little threads always scare me. In reality it's not like I find myself needing to take the motor off with any regular frequency. It's just a situation that I was faced with this summer.

The way that I imagine it, the half that stays on the bike wouldn't need to be very big. It could still be retained and wouldn't get in the way because it would be within the diameter of the chain ring. And in my particular case it's needed since it holds the chain roller/guide. I attached a crappy ms paint pic depicting how I imagine it. The areas between the red arcs depict an area where the removable and the affixed portions of the plate might overlap for lateral torsion resistance(maybe even a close tolerance shoulder incorporated so that the two sections of the plate where they mate might add resistance to radial force) . Red circles indicate where a few bolts might hold things together.
GT Right plate modular.jpg


I'm not saying or suggesting there is any demand here for this, it's just something I thought about for my bike. I one of those guys who likes to ride his own kit. I like the familiarity and memories to me made be on my bike. So it got me thinking about how I could take my bike and ride it as electric and DH next year, and not have to rent.

The one thing that I'm really searching long and hard for is a bulletproof SS 24T chain ring for the crank. The aluminum ones from sick bike are just too soft imo for the kind of power this thing puts down, and the non standard bolt pattern is a concern for off the shelf components.
Fat bike crank tangentmotor.jpg
The fat bike crank pic from your site has a different inner chain ring and spider. Is that standard bicycle bolt hole spacing?
IS that spider something that would bolt on to the sick bike parts UHD freewheel? What is the BSD of the spider? Does this spider lead to an altered chain line?

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Re: Dave's 80:1 RC mid drive kit build log

Post by morati » Dec 24, 2017 4:52 pm

Beautiful work as always Dave! Curious as to why so many changes? My 3k watt PAS kit is performing perfectly. As a matter of fact I did a 2hr. trail ride today on approx. 6 inches of fresh powder with temps at about 20 degrees F. Motor got to a whopping 65 degrees F. Went through less than half of my 10Ah 14s lipo battery.
When do you think the new 3210 kits will be out? Considering getting another one from you so the wife can have mine.

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Re: Dave's 80:1 RC mid drive kit build log

Post by tangentdave » Dec 24, 2017 6:41 pm

I needed to redo the CNC setups to make machining easier, so I took the time to address the issues in the first design. The new gearbox is functionally identical, but a host of small changes make things easier and simpler, and quieter. There's not an engineering playbook for designing cycloidal gearing, even the academic literature pales compared to the conventional pinion/spur and other involute arrangements. There's an equation to generate a perfect circular cycloidal spline, but little guidance on how to produce such a gearbox with real world tolerances, especially using input speeds that small diameter motors need. Nor has anyone told me how to design the reducer into the smallest volume possible. Eccentric gearing is obviously the way to go to enable our desire for power in small size; it's far more robust and compact than other speed reducer options (and obviously a speed reducer is needed in the pursuit for the lightest ebike/eMX).

Once these parts are verified, I'll make a few more copies for on-bike testing, then we're ready to roll. The chainline and BB hardware is about locked in (the Cyclone FW has proven tougher than the single bearing White HD FW, not sure the price of the White UHD double bearing FW is warranted, do you guys pay an extra $60 for a White FW?)

-dave
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Re: Dave's 80:1 RC mid drive kit build log

Post by tangentdave » Dec 24, 2017 6:47 pm

must cost a fortune?

Not my intention. Small batches increase price, so do quality components. Cost of both will decrease with volume. How much is it worth to be riding on the good sh*t in the meantime?
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Re: Dave's 80:1 RC mid drive kit build log

Post by Mugenski » Dec 24, 2017 9:47 pm

12-C wrote:
Dec 24, 2017 4:25 pm
Nice work Dave!

If it wasn't for that I'm sure I'd be skipping my necessary chain maint.... that's just how it goes for me lol.
I'm feeling the same. My dualsport MC gets no love, just enough maintenance to keep it from giving up entirely. Having to oil the gearbox on my bike gives me a reason to also spray the chain down and relube. That said I do love the inclusion of a grease/oil retention system.

This kit is so mint it's not even funny. Dave, my dollars have be well spent and I thank you for your work. Your time and perfectionist attitude really get me excited. I too was questioning the thermal interface between the astro and case. I LOVE that you have addressed this as well as the grease seals in gen 2. Freaking awesome. I had thoughts about the interface and how to improve it. Alas I should shut my mouth and observe :wink:

I struggle now with 2 choices, I really wanted to ask for a set of his "2 stroke mx" sounding gears however with Gen2 here, I am in a pickle. As a MC enthusiast I love the sound of the older kit and Daves audible tuning. However Gen2 draws me in for the technical (thermal?) aspects.

Gah stop making such a gem of a kit! I don't need more choices!
Last edited by Mugenski on Dec 24, 2017 11:47 pm, edited 1 time in total.
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Re: Dave's 80:1 RC mid drive kit build log

Post by BonesNis » Dec 25, 2017 2:48 am

Hey Dave

Still looking at pre-orders in December or will this stage be pushed back until the new year? Very anxious to get my hands on the second gen 6kw Ascent. Thank you for the updates and tireless work improving on a immensely well engineered mid-drive.
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Re: Dave's 80:1 RC mid drive kit build log

Post by spiros » Dec 25, 2017 12:40 pm

Very very very nice job Dave.
My compliment for this great motor. I think that it worth every single euro 💶
I own a couple of cyclones modified from my self and obviously are garbage in front of your Ascent but with my experience I could confirm that I never felt the necessity to have a removable motor even with the cyclones that are bigger and heavier.

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Re: Dave's 80:1 RC mid drive kit build log

Post by tangentdave » Dec 25, 2017 2:41 pm

Going to miss my december due date, not by that much though. I want to show the testing, guesstimate a lifetime of the gearbox and lube schedule. You guys are buying hardware and should see how well it works and exactly what you're getting for the money. I'll post updates to the thread more often, just a couple weeks longer...

We do need a higher quality 24t chainring. The soft cheapo one from Sickbikeparts is only like $5 and seems to last at least a while, although a worn sprocket will wear the chain faster. The bolt pattern for the SBP 24t is 5x2.63", which is the standard bolt pattern for the threaded freewheels, it uses the same bolt holes as the spider I make to attach to the crank FW.
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Re: Dave's 80:1 RC mid drive kit build log

Post by 12-C » Dec 25, 2017 11:43 pm

tangentdave wrote:
Dec 25, 2017 2:41 pm

We do need a higher quality 24t chainring. The soft cheapo one from Sickbikeparts is only like $5 and seems to last at least a while, although a worn sprocket will wear the chain faster. The bolt pattern for the SBP 24t is 5x2.63", which is the standard bolt pattern for the threaded freewheels, it uses the same bolt holes as the spider I make to attach to the crank FW.
Can you point me in the direction of the threaded free wheels you speak of? I'm not familiar.

There seem to be some 64BCD chain rings that are 4 bolt and are available in steel. At 64mm it seems like it would be just 1.4mm in radially (2.63") which might fit with the current spider, no?

Had another look at the fat bike chain ring on your site, not sure what I was seeing differently the first time...

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Re: Dave's 80:1 RC mid drive kit build log

Post by tangentdave » Dec 26, 2017 11:34 am

http://sickbikeparts.com/front-freewheel-cyclone/

The spider in the picture you're talking about used a 64mm BCD chainring and a 104BCD ring, it was a pain in the ass arrangement. The cheapo 24t sprockets are way easier even if they are softer.
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Re: Dave's 80:1 RC mid drive kit build log

Post by 12-C » Dec 27, 2017 12:18 pm

I've recreated the spider in CAD

I'm waiting on a response from the blackspire regarding the bolt hole size for mounting the 74BCD chain ring https://www.blackspire.com/product-cate ... /ss-chuck/

I'm going to try and design a custom spider that can allow for mounting on the 2.63"BCD of the freewheel and also accomodate the 74BCD of the SS chain ring.

If anyone has any suggestions for design or considerations please feel free to chime in.
Spider 74BCD mod v1.jpg
(74.19 KiB) Not downloaded yet

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Re: Dave's 80:1 RC mid drive kit build log

Post by tangentdave » Dec 27, 2017 2:14 pm

Chainring bolts are 10mm diameter (I cut a 10.1mm bore) and the profile to countersink the bolt should be 13mm diameter and 1.5mm deep.

Perhaps it'll be easier to laser/waterjet a sprocket out of stronger steel rather than stuff more features onto the spider. Don't forget about the flange on the FW that'll interfere with granny ring bolt circles (have to modify the flange somehow or put the granny ring far away).

Or, duh, maybe we can just drill the Blackspire ring to accept the M5 5x2.63mm bolts...
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Re: Dave's 80:1 RC mid drive kit build log

Post by 12-C » Dec 27, 2017 4:15 pm

tangentdave wrote:
Dec 27, 2017 2:14 pm
Chainring bolts are 10mm diameter (I cut a 10.1mm bore) and the profile to countersink the bolt should be 13mm diameter and 1.5mm deep. Thanks

EDIT: I just loaded the picture from the website into CAD and taking the relation of the known BCD=64mm I calculated the hole to be M8, which is exactly the size of the male portion of the chainring bolts. Granny rings are often just held in with the male bolt,, foregoing the female portion. As I think is the case here.

Perhaps it'll be easier to laser/waterjet a sprocket out of stronger steel rather than stuff more features onto the spider. Don't forget about the flange on the FW that'll interfere with granny ring bolt circles (have to modify the flange somehow or put the granny ring far away).
Yes I would tend to agree. The only reason that I favor modding the spider is so that off the shelf chainrings can be purchased in many different flavors. Regarding the flange on the freewheel, I will probably have to recess it a bit if it's a thru hole design or create some threaded bosses so that the sprocket bolts can be just threaded into the spider. Personally I'm not a fan of threading anything into aluminum unless there are some helicoils present. In the case of a threaded design It would mean that the spider is non reversible and fine tuning with shims for the chainring may be necessary, not exactly a problem for my setup. Again I'm not exactly thinking about a mass produced piece that is has some inherent flexibility in it's design for adapting to fit many different bikes, but just something that will be more suited for my bike.

Or, duh, maybe we can just drill the Blackspire ring to accept the M5 5x2.63mm bolts...
That would be idea it looks like the inner portion of the chainring is cut away except in the areas of the 64mmBCD, it looks to me that there is no room for that.

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Re: Dave's 80:1 RC mid drive kit build log

Post by 12-C » Dec 28, 2017 2:48 am

I'm going to give the SBP 24T chainrings another try. I'm going to assume that the premature failure had a lot to do with the couple times I had debris get stuck between the chain and caused the chain to skip and dislodge.

And I had another look at the chainrings, they are in fact steel, although they might very well be mild steel unlike the ACS freewheel that looks next to new compared to the mangled chainring....

Worst case scenario I might draw up a chainring and have it cut from something tougher if it comes to that.

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Re: Dave's 80:1 RC mid drive kit build log

Post by spiros » Dec 28, 2017 3:03 am

Another minor question is the throttle.
Despite the undiscussable quality of dominos throttle many downhillers like to have a direct feeling on the handbars gripps without any interference as when gravity pulls down I don't mind of the superwonderhulklike tangent motor but i need to dominate my bike over jumps and rocks.
So the question is, could it be possible to have also a thumb throttle over/beside the domino?
Thank you, Dave
Anyway I agree that it is extremely important having the possibility to use standard bike equipment and I know that on the 104bcd I can use a 30 teeth of chainring and I can use the http://sickbikeparts.com/freewheel-spider-4-arm-104-mm/ so why I cannot use this spider for both bottom brackets chainrings using longer chainrings bolts?

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Re: Dave's 80:1 RC mid drive kit build log

Post by dtx » Dec 28, 2017 7:55 am

A thumb throttle should be easily possible, at least with the CA in use. That beeing said, the only thumb throttles i know are plastic and very hard to control, i wouldn't want that on a 1kw drive let alone a 6kw monster tangent. But maybe there's a higher quality one out there.

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Re: Dave's 80:1 RC mid drive kit build log

Post by ferret » Dec 28, 2017 9:52 am

I'm using this type of throttle:
https://www.aliexpress.com/item/WUXING- ... 0.0.s9RlY0

Mounted on the left where a front shifter would normally go.
Reasonably easy to modulate and it isn't effected by pulling on the grip.

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Re: Dave's 80:1 RC mid drive kit build log

Post by 12-C » Dec 28, 2017 2:06 pm

I have one of the grin thumb throttles. I purchased it at the same time as the half length twist. Never mounted it. Coming from both a motorcycle and bicycle background after switching to the half length twist throttle I would say it's the best compromise. You can still maintain a good solid hold of the bars and not upset with throttle inputs in the hairiest of terrain. I would not want to do the same with a thumb missing from the grip equation. My 2¢

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Re: Dave's 80:1 RC mid drive kit build log

Post by dtx » Jan 01, 2018 6:48 pm

Hey Dave since this is finally happening soo soon, may i reserve serial 0042 for vanity reasons? ;)

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Re: Dave's 80:1 RC mid drive kit build log

Post by tangentdave » Jan 02, 2018 5:18 pm

The 007 of the ebike world.

We can easily switch from using a 16/24t for the chains to 20/32t (the reduction ratio moves from 1.5 to 1.6, no biggie). 32t can use the 104BCD spiders. The 20t freewheel is heavier than the 16t (141g vs 185g), the 24t steel is heavier than a 32t aluminum (71g vs 41g), plus a few extra 11spd links, so it really is samsies.

Just now I found the batteries were dead in this kitchen scale I have, and of course guess what the cells are? Button batteries. wtf? Button batteries? Come on. 32t aluminum at the crankset it is.

And there's also this:
20180102_140508.jpg
20180102_140508.jpg (121.5 KiB) Viewed 253 times
20180102_140453.jpg
20180102_140453.jpg (88.4 KiB) Viewed 253 times
This is an adapter we screw the FW's onto. It's not fully threaded so the FW won't pass all the way over it. Two short 5mm dowel pins act as our keys. The output of the gearbox is threaded M6 and passes through into the inside (oil port). These threads will hold the adapter against the output. The adapter is threaded M8 so we can use a bolt to pull the FW assembly off the output easily. Previously the FW was threaded onto the output piece which meant the gearbox had to be disassembled to unscrew the FW. Now we can quickly alter the motor's reduction ratio to better match the situation.


-dave
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Re: Dave's 80:1 RC mid drive kit build log

Post by Buk___ » Jan 02, 2018 6:01 pm

tangentdave wrote:
Jan 02, 2018 5:18 pm
The 007 of the ebike world.

...
-dave
I apologise in advance if I've missed the point, but ... wtf?

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Re: Dave's 80:1 RC mid drive kit build log

Post by tangentdave » Jan 02, 2018 7:07 pm

His code number? Like, you know, a special agent? But for ebikes.
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Re: Dave's 80:1 RC mid drive kit build log

Post by macribs » Jan 02, 2018 7:15 pm

I think the 007 was clear, it was more the reference to the ebike world I think was hard to grasp. For me that was the case at least.

In any case that should make you the Q of e-bike? :wink:

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Re: Dave's 80:1 RC mid drive kit build log

Post by tangentdave » Jan 02, 2018 9:49 pm

I'll be Q. What's dtx gonna do with a 00 number, License to Pass?
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Re: Dave's 80:1 RC mid drive kit build log

Post by macribs » Jan 02, 2018 10:26 pm

He was asking for 00420? License to toke maybe?

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