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

Dave

Any issues with moisture or dirt with the exposed controller?

Thanks.

Any issues with moisture or dirt with the exposed controller?

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Not after you dip it in magic.

Glad to see it's being put to good use

What is the total weight of the 3220 6kw peak version with Bottom bracket and chainwheels ? i want to see how it compares to the BBSHD which has the chainrings and BB attached also. i.e so the complete weight of the kit on the bike. And also what is the 3210 3KW version total weight?

Also what BB width is used on this, is it the 148mm wide ISIS BB?

10-10.5lbs. I'll confirm this round with a pic. The ISIS BB and White freewheel on the crank aren't the lightest, but they are tough.

ok so then when comparing the exact same things, i.e everything with controllers mounts and bottom bracket etc its only few pounds heavier then the 8 pound BBS02? But its less then the 13 pound BBSHD? yeah those 148mm ISIS bottom brackets are not that light.

Dave

How much space (in mm) is there between the frame at the bottom bracket and the interior chain ring when mounted? Thanks.

We can adjust the chainline with the spider a bit, but the intention is to place the inner motor sprocket 6mm off the outside face of the mounting place (which is 6mm thick and abuts the BB face).

-dave

Dave

Any updates with regards to your kits, thanks.

tangentdave said:

NTCE is willing to produce the ISIS version in the correct spindle length to fit the kit (we need 30mm of spindle stickout on the chain side, plus 6mm to accommodate the mounting brackets, their existing dimensions aren't compatible with the freewheel crankset). There would be some costs associated with the custom part that I have to figure a way to cover, I want the ISIS version too.
-dave

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Dave,
It's been a month and I've been waiting on updates on the NTCE ISIS. Also, do you have dimensions on the total width of both the 3k and 6k versions? Does the 6k version still fit within/inside the cranks?
Thanks!

When I say costs associated with the custom ISIS spindle, I mean an MOQ of 100 units at $240 each and $10k in NRE. $30k is waaaaaay more money than I have. The ISIS version of the THUN does not fit the kit at all because it's sized for only 68mm BB's and the Tangent housing is set up for 73mm. The 3kW version fits within 128mm wide BB spindle, the 6kW fits within 148mm wide spindle. Luckily, the square taper THUN is available in 128mm and fits the kit after I shave 3mm off the left side crank. NCTE produces both the square taper and ISIS torque sensing BB's available through Grin, the sensors and functionality are the same, the bicycle interfaces are different. The square taper THUN is holding up to my beating nicely and I haven't had to tighten the crank bolt once (ISIS interface requires regular attention).

I'm building the next round now, with improvements. Will detail upgrades shortly.

-dave

Thanks for the update. Waiting impatiently for my drive. I'm not real good with Christmas either.....

Cross post:::
https://endless-sphere.com/forums/viewtopic.php?f=28&t=87066

[youtube]3CiedEiQwl4[/youtube]

litespeed said:

That looks nice and light.

Tom

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Haha, thanks! But to be completely honest that Specialized frame is heavy AF! It's 4130 double butted chromoly which means it can get ran over by a dump truck and still be ok! LOL....I ended up taking it off the specialized and putting her back on the Tracer now that she's fixed (long story).

MTB's are so playful with this much power, just lean back and let the front come up. So. Much. Fun.

Update coming shortly. Thanks for everybody's patience.


-dave

Dave,

Since you seem to definitely have some skills designing and machining aluminum, have you ever considered designing an adapter for the freewheel at the crankset that uses the latest RaceFace cinch BB ? It would be nice to get rid of this heavy ISIS BB and be able to use carbon crank arms. I am sure we could save almost a pound. I tried to reach out to KRANKED but so far no answers. I know they do make it but I am not sure if they are willing to sell them as a spare. :?

I plan to replace that heavy ISIS crankset, the parts needed aren't difficult. Logistically, my plate is full of gearboxes right now but a complete custom kit is the goal.



The Tangent mounting plates add 3mm to each side of the BB shell, our spindle and bearings need to accomodate this. The crankset also needs enough spindle stickout to accommodate the freewheel.

tangentdave said:

I plan to replace that heavy ISIS crankset, the parts needed aren't difficult.

Click to expand...

I'll def be among the first to order the new crankset when available! Or if you need a beta tester lmk!

Same here on both accounts!

New round of units going out, these include some changes I've been working on over the winter.



Old on top, new on the bottom. The 6806 bearings are a bit small, so in with 16005 ZZ C3, oh yea. These are twice the strength, C3 clearance for high speed and temps. They're a touch wider so I had to re-do the other pieces. These gears are 7075 Aluminum running against a steel ring gear. Steel for the eccentric gears is overkill, thousands of miles and they look brand new. Shown here is the eccentric assembly with steel gears blued from hardening.



I'm going to produce the 40:1 ratio for all the kits. This ratio is a great starting point as we can easily achieve overall ratios to the crankset of 44:1 all the way to 95:1 using commonly available freewheels and chainrings. This updated design fits all existing gearboxes. If someone has an issue with their 6806 bearings, they'll get the new design.



By reducing the turn count of the Astro motors by 1, we can shift more work to the gearbox and generate less heat in the motor, by quite a bit. A 4turn 3220 has winding resistance of 0.032ohm while a 3turn is 0.019ohm, almost half. The previous 3220's were 4turn and overall 40:1 ratio; the 3turn will run at 55:1 overall to produce identical performance figures, but for longer because of less heat. Same goes for the 3kW kit, instead of a 7turn at 55:1, we'll use a 6turn at 75:1. Another upside is 12s packs work great. 14s is bonus now.

Aluminum gears are 40% the weight of steel but as strong as a mild steel. New gear profile has quieted things down and 10% more output pins increases efficiency and robustness.

[youtube]8DYuSvJ-CUw[/youtube]

Oh, new spring loaded tensioners too.


-dave

Great update, new bearing looks very robust.
How many gears do you normally use during your rides? I ask because I'm wondering if you recommend gearing for the rear cassette?
I presume the rider application/ terrain has a bearing on rear cassette config.

I do recommend a cassette, who doesn't want more torque in most situations? You need a chain to transfer power to the wheel already...

We seem to have closed in on 35mph being about a good top speed for 6kW. HPC, LunaCycle, Stealth all run their 5-6kW bikes to around 35mph. With a 6kW mid drive to a cassette, that's about 5th gear. Meaning you have 4 choices for more torque when you're riding slower and a few choices for more speed when you're cruising.

Looks great Dave...

Is that a 3220 or 3210 motor?

Really great work Dave.
That was already a great kit when released, and to see all the time & effort you put into keep making this kit even better is just amazing.

Thanks, I'm trying. Who knew producing a 15kRPM gearbox would be so finicky? Every detail on every part is important for smooth operation. I spend more time on process improvement than design.

The videos still pick up all the sound, it's maddening trying to convey what's it like to ride, you'll have to take other people's word for it. The Tangent gearbox is now quiet, less than a cyclone gearbox for sure, and I run higher RPM. The motor in the video is a 3210. I'm going to run all the motors at 225kV, that's a 12turn 3205, 6turn 3210 and 3turn 3220.

12turn 3205
1.6lbs motor/5.2lb drive weight
225kV = 11,700RPM @52V
40:1 internal, 2.14:1 secondary (14t->30t), 85:1 overall
138RPM max cadence
30A phase = 180in/oz shaft torque = 80ft/lbs @ crankset; 120W peak heat

6turn 3210
2.2lbs motor/5.8lb drive weight
225kV = 11,700RPM @52V
40:1 internal, 1.875:1 secondary (16t->30t), 75:1 overall
156RPM max cadence
60A phase = 360in/oz shaft torque = 140ft/lbs @ crankset; 162W peak heat

3turn 3220
4lbs motor/7.8lbs drive weight
225kV = 11,700RPM @52V
40:1 internal, 1.33:1 secondary (18t->24t), 53:1 overall
221RPM max cadence
110A phase = 660in/oz shaft torque = 182ft/lbs @ crankset; 230W peak heat