Oatnet's 'Kepler Friction Drive' build

[oatnet]

I've posted a bunch of builds here on E"S, but this is my first foray from the world of 'frock' motors into the world of 'skirt' (bearing) motors so I expect I have a lot of magic smoke in my future... but I have high hopes for this elegant design. I spent a bunch of time yesterday assembling the test mule from bits about the shop, even though I wasn't expecting it for a while. Turned out to be just in time because the Kepler drive arrived today. I I did I test fit and took some pics to share.

I bought the Alex DX-32 wheelset from ebay because they were $134 shipped, less than it would cost to have a just the front laced. My cluster was too small for the freewheel so I put on only the smallest gear, only one I use anyhow maybe I'll save a few ounces. I took off the gripshift and cable too. Although I saved money, I spend $40 on a 10mm through-axle for the rear wheel, and the centermount disks are $30+, tacking $100 onto the build.

The frame is recycled from an earlier prototype, so it was already equipped with my Preferred dimension 120mm adjustable stem and 'On-One Mary' handlebars. I added a set of Rock Shox Boxxers which turned out to be a good color match to the TF frame and really punch it up. The new-style Ergon GC-3 grips should let me really stand up and glide.

I have the luxuriant thumb throttle from a Tidalforce (0-5k pot), I have to wire up the servo tester so I can control the esc. I also need some plugs to solder onto the ESC, or just swap the ones on the motor with Andersons, the wires are too long anyhow.

After I get it going I need to make it stop. I have a set of Gatorback brakes from Methods to put on here, gotta buy adaptors front and rear, swap the brake levers left/right, grind off the torque arm bracket, and buy a centermount disk to fit.

I think I am going to parallel the 48v ammo-can pack from my BMC build into a 24v/32ah pack for this build, tons of WH for tons of range, and with a123 prisimatic quality I can charge the pack in 1/2 hour.

The accessory area under the ESC is 80mm x 40mm x 35mm, or 3.36" x 1.58" x 1.40", which makes it too small to hold the Evlogix throttleizer, which is 3.4" x 2.2" x 1.4" http://www.evlogix.com/content.php?link=Rcthrottle

-JD

[AussieJester]

Is it just the picture or are those wheels different sizes? Shouldn't the big one be on the front and the lil one on the back Oatnet? YPedal MaN will not be pleased

Seriously though, nice setup mate, very stealth looking keen to hear your impressions of the setup when you have had a good ride on it, i doubt you will have any magic smoke issues with the HV100 ESC if you ride as per the Kepler unit is designed for, i.e pedal to start before applying power...

KiM

EDIT: be sure though to add a extra cap across the '+' and '-' input wires of the hv100 if yoiu haven't already, i know your a frock boi pro not sure if your up on the rc esc protocol yet?

[oatnet]

Same 26" Maxxis Hookworms/rim/spokes and matched hubs, so it must be the picture or some of that fine aussie brew. Probably an illusion from having so much stanchion exposed, or maybe you are thinking of JRH's build:



The pedal-first thing may be my downfall, I'm used to just riding without having to worry about accomodating the technology, we shall see. If I can't learn I'll have to fit up some hall sensors, or see if a throttlizer will help.

I did see that bit about adding caps, and I saw the bit about mounting them close to the ESC so the legs don't melt off. I wonder if simply building up the legs with some soldered copper braid would solve the proximity issue, and I wondered if I could simply mount the cap on the pack side of the battery lead, if there isn't enough space inside the Kepler drive.

-JD

[kevo]

Oatnet,
Please don't hesitate to spell out a step by step gory detail of a Kepler install for those of us with less install experience. Just received my Kepler build, have an ESC and motor but am searching around for pdf instructions.
Excited but slow builder,
Kevo

[Kepler]

Oatnet, looking good. Glad every thing arrived safely. Nice bike.

The drive is sitting a little high on the tire with that bike's geometry. Getting the motor a little closer towards the seat stays will drive the motor more firmly into the tire under load. This can be achieved by offstting the clamp mount to angle the drive down a bit more. You can then move the drive down a little on the seat post. Perhaps try in the stock position first and see how it goes, but the option is there. Dont forget the grip tape

Also with the Castle Creations ESC, trim a little of the heat shrink off so the heat sink can make firm contact with the top clamping plate.

[Kepler]

In relation to the Caps, there really isnt room inside the drive. That being said, all my testing has been done without Caps added and never lost an ESC yet. The caps have been an important addition to RC setups and I do not dispute their use. However, at 5S or 6S, I am speculating that the ESCs are seing less ripple then with the 12S setups where these failures have been documented. Also the battery cables have alway been kept short with a 6" extension being the the max I have used.

Keep in mind the throttleizer has ripple caps already installed.

[oatnet]

Kevo, will do. The drive is pretty simple once you have been through it and see what goes where. Kepler should have sent you his instruction PDF.

Kepler, I originally installed the mounting clamp to the rear pair of holes, to get it closer to the seatpost. Today I tried angling it between the bottom rearward holes, and the top frontward holes, and after some cursing I finally got it to slide through. Now it is more steeply inclined, but further from the seatpost clamp, is that what you were suggesting?

I was going to ask about that extra bit of material on top of the ESC - off it comes.

I am thinking about the grip tape, but first I want to see how the massive inverted-tread contact patch from the hookworms performs before I start blocking cooling with layers of stuff. Also, it seems to me that I saw some spray-on grip texture which I might try - I can envision that grip tape delaminating from a hot motor in a messy way.

The throttleizer may have ripple caps, but it won't fit in your drive - looking forward to your electronics!

Anyhow, got the front brake on this morning, gonna try to solder up the electronics.

-JD

[etard]

Very nice setup, clearly you know what makes a good ebike. I'm just wondering if that frame isn't too small for you, only because it looks like the seatpost and handlebars are raised as high as possible. I'm also looking at the linkage on that thudbuster and wondering if a battery tray could somehow be attached at these points.

I see you are in Socal, where at exactly? We should get a meet going sometime, there seems to be alot of guys in this area.

[kevo]

The Kepler Drive, the Boxxer Forks, the wheels - excellent build Oatnet!
Quick question, the Turnigy C6374 has a bolt on bolt that mates w/ Kepler's blue bearing.
Did you have to grind down the bolt to mate with the bearing? Or how did you resolve?
The Tidalforce builds continue to break barriers with all the new RC builds!

[oatnet]

kevo, I suspect you need to remove the 8mm slip-fit adaptor out of the blue bearing, so your 10mm propshaft will fit through. Thanks for the good words, etard too!

Here is my attempt at an assembly manual. You need 2.0mm, 2.5mm, and 3.0mm hex wrenches, a small crescent/adjustable wrench, and soft work surface.

My drive arrived partially built, so this is what I did to finish it. Kepler and others please correct any errors/ommissions and I will update the post to fix them. I think there are a number of areas I will apply locktite blue once I get things sorted out. Also be wary of the set screws - they come out easy, and I have to find one before I can use my drive.

-JD

- Red marks indicate bolts needed for removal.
- (4) bolts require a 2.5mm hex wrench.
- A 2.0mm hex wrench opens the tiny bolt, top center. This and a matching bolt on the other side slide up and down in the slot to adjust to different size ESC's.
- Two bolts secure the seatpost clamp to the body, you will need an adjustable wrench for the nylock nuts on this side, and a 3mm hex wrench for the other side. These bolts may slide out and spill the spacers all over the place. Note that the bolts can go through the rightmost holes, the leftmost holes, or one from each column, to adjust to different mounting angles.

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Here is the removal of one of the bolts with an adjustable wrench and a 3mm hex wrench, I mostly did this shot so you could see the spacers on the the seat clamp bolts.

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1) With the bolts removed, lift off the right side plate, and insert your ESC. Kepler added: "Make sure you get the ESC clamping plate square so it contacts as much of the ESC heat sink as possible. I presume cutting away a bit of the heat shrink on the ESC would have helped this." I know there is a raised end I have to flatten on my Castle, I will go ahead and lap the top fins flat and use thermal compound to maximize heat transfer to the drive body.
2) Route the motor cables out the back,the battery/throttle cables to the space under the ESC and perhaps out the hole in the front of this chamber.
3) Reassembly is the reverse, put it back together.

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1) If you have a 63mm motor like mine, buy (4) M4 x 20mm bolts. My local Ace Hardware only did the hex version up to 16mm, had to buy bolt head. I think the (4) smaller bolts supplied with the kit will bolt the arm directly to the base of the 45mm motor.
2) Replace the bolts securing the base to the motor with the 20mm, and use them to secure the arm to the motor as shown. It looks like orienting the cable output as shown will provide the shortest path to the ESC phase wires.
- The bolts I removed from the motor are loose in the lower part of the pic.

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Install the bolts and prophead that came with the motor.

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Like So!

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1) The shaft, spacers, and locking collar are shipped together as a unit. Remove the lock collar and spacers from the shaft
2) Insert the shaft into the front side of the left lever. When I had the shaft flush with the side of the body, I didn't have enough room for the motor on the other side, so, it is recessed a little bit as shown.
3) Secure the shaft with lock screw, and slide on (1) of the spacers.
- When finished, your drive should look like above.

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- The pad retaining disk is in the way of installing the left arm.
1) Use a 2mm Hex wrench to remove the bolt for the pad retaining disk, and remove the disk.

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Slide the arm/shaft/motor subassembly onto the body, and bolt the pad retaining disk back on with a 2mm hex wrench. The arm will now be unable to slide off past the pad retaining disk. The pad damps motion in both directions, hence the L-shape of the left arm, very clever design.

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1) Slide the other short spacer on the top bar, followed by the other lock collar, and use a 2mm hex wrench to bolt its set screw down.
2) For my motor's 10mm shaft, I had to slide the 8mm adaptor out of the blue bearing, and slide the 10mm washer onto my propshaft. Motors with 8mm motors will slide right onto the adaptor and don't need a washer.
-Note to kepler: the scotch tape used to secure the insert in the bearing made a gummy mess. Painters masking tape might work better.

9_0653.JPG (58.85 KiB) Viewed 3197 times

1) Slide the right arm onto both shafts
2) Secure the right arm's locking collar to the shaft, with a 2mm wrench on the set screw.
3) slide the kepler kit long spacer onto the prop shaft, snug against the bearing, and use the nut that came with the motor to bolt it down tight.

a_0655.JPG (29.17 KiB) Viewed 3197 times

[MrBoots]

Oatnet, great-looking build there. I wonder how much weight total you've added to the bike. Kepler's drive seems to be the ultimate light-weight setup.

BTW, the Turnigy 63-74 is one awesome outrunner. I know others have had reliability issues with the Turnigy motors, but I've logged about 700 miles total with mine (some incredibly hot and brutal) and it's held up incredibly well. I've also been using the Phoenix ICE 100 for about a month now and that's worked wonderfully too. I'm sure you'll be very satisfied with that combo.

[Kepler]

Nice Job Oatnet. I am going to do some cut and paste here and add it to my manual. I would have liked to have done something similar but I just ran out of hours in the day to get this done before they shipped. Glad I could rely on you guys though to get this together.

Make sure you get the ESC clamping plate square so it contacts as much of the ESC heat sink as possible. I presume cutting away a bit of the heat shrink on the ESC would have helped this.

And check, use different tape

In regards to angling it down, what you have done is what I meant so that’s good. The idea is to get the roller a bit lower on the wheel circumference. This will encourage a firmer engagement under load.

Post a picture of the drive position on the bike with the steeper angle if you could. I would like to see how it sits.

[Hillhater]

question .!
why do you use the prop adaptor on the "drive" end of the motor into the bearing ???
On the 63 dia motors the prop adaptor is 10mm, same as the main motor shaft, so its simple to move the shaft through the motor stator and use it direct in the bearing.
This simplifies the assy, saves 10-15 mm on width, and eliminates a potential weakness ( that alloy prop adaptor is not designed for these "normal" loads )
An added bonus is you can use the 4 mm cap heads that come with the prop adaptor , to secure the motor to the side plate !

[oatnet]

An added bonus is you can use the 4 mm cap heads that come with the prop adaptor , to secure the motor to the side plate !

The 16mm M4 screws that came with the motor were just long enough to grab a thread, but not enough to be secure. I'd stick with the 20mm in either case.1

Is it that easy to slide the shaft? That would make for a simpler design, but I haven't had one of these motors open yet. Since I reckon the design of the one in my hands isn't gonna change, I think I'll just cut the shaft off in my metalworking class, and eliminate a rotating hazard.

[Hillhater]

To move the shaft you do not need to dismantle the motor.
there are 2 tiny (2mm ?) grub screws between the "fan blades" on the "prop" end that you loosen, ( Take care to back the grub screws off enough to clear the flats on the motor shaft !),
..then you can push the shaft through to a suitable position and re tighten the grub screws.
5 mins , job done. !
The M4 screws that secure the prop adaptor are long enough at 15mm to fix through a 8 mm plate if necessary.

[oatnet]

Nice Job Oatnet. I am going to do some cut and paste here and add it to my manual. I would have liked to have done something similar but I just ran out of hours in the day to get this done before they shipped. Glad I could rely on you guys though to get this together.

Make sure you get the ESC clamping plate square so it contacts as much of the ESC heat sink as possible. I presume cutting away a bit of the heat shrink on the ESC would have helped this.

In regards to angling it down, what you have done is what I meant so that’s good. The idea is to get the roller a bit lower on the wheel circumference. This will encourage a firmer engagement under load. Post a picture of the drive position on the bike with the steeper angle if you could. I would like to see how it sits.

Glad to help, feel free to use anything in that guide you like. I am sure all of your customers would rather have you boxing shipments than making manuals.

I was thinking of lapping the top of the ESC heatsking smooth and using thermal compound to maximize heat xfer to the body.

I remember you writing something about how important getting 'over-center' was to locking in the drive. I am getting feel for the range of positioning, but I don't have a clear view of what 'right' looks like. I was quite surprised when the seatpost mount bolts actually fit through the holes diagonally... Oversized holes? Here is the remounted drive:

[oatnet]

BTW, what is the size of the set screws? Looks like I need to replace the one I dropped. Ace Hardware, my usual source for mystery bolts, does not stock metric set screws so I'm screwed. Or not.

-JD

[Kepler]

The over centre locking action was used in earlier designs but I found it wasnt needed. It made the drive engage and disegage with a clunk. The damper makes the for a much smoother action and gives you variable pressure on the tire for a given load rather then being all or nothing.

I think the angle is too much now. Go back to the staight alignment but use the back holes. You can the motor to sit a little closer to the seat stays by triming the damper into a D shape if you need to. See the picture below.

In relation to the set screw, I presume you mean grub screw. They are 4mm. You should be able to get them easy from a dedicated bolt supplier. Also try a hobby shop. They are used in RC helicopters all the time.

[kevo]

Hillhater,
Your advice on moving the 6374 shaft is much appreciated since Hobbyking sent me a 12mm prop adapter. Also agree the aluminum is not as strong.

Oatnet,
Many thanks for your excellent photos and build details in such short order.

Kepler,
Awesome product, can't wait to get it on the road!

[Kepler]

question .!
why do you use the prop adaptor on the "drive" end of the motor into the bearing ???
On the 63 dia motors the prop adaptor is 10mm, same as the main motor shaft, so its simple to move the shaft through the motor stator and use it direct in the bearing.
This simplifies the assy, saves 10-15 mm on width, and eliminates a potential weakness ( that alloy prop adaptor is not designed for these "normal" loads )
An added bonus is you can use the 4 mm cap heads that come with the prop adaptor , to secure the motor to the side plate !

Its a good idea Hillhater. I am going out to the workshop to try it right now. The only thing I dont like about the idea is that you dont have the ability to tie it all together with the 10mm nut and you end up relying on 4mm grub screw only. Time for some testing

[Hillhater]

. The only thing I dont like about the idea is that you dont have the ability to tie it all together with the 10mm nut and you end up relying on 4mm grub screw only. Time for some testing

Kep' .. there is not much holding these motor ends together anyway ,---mine "slipped " apart without me forcing it !
but you could always put a lock collar on the outer end of the shaft ..or ultimately thread both ends of the shaft !

[Kepler]

OK, some quick testing done.

Firstly the process of moving the shaft. Not too difficult. You need to remove the end bell where the wires come through and remove the small circlip and washer from the shaft. Then loosen the 2 grub screws on the other end.

To tap the shaft through, put the motor on its end with wire side up. Use a block of wood with a 12 mm hole in it for the shaft to go into once you start to tap it. Knock it through so that around 15mm is preluding.

Don’t try and hold the motor in your hand and tap the shaft through as this will dislodge the ring bearing.

Re assemble the motor and re fit the motor into drive. I would recommend some medium strength locktite on the pivot arm grub screws just to make sure.

The assembly still feel very ridged. I did 1 pack through the drive with this setup and all held together well.

So far so good but if you do this modification, please make sure you check the drive closely after each ride until you are completely confident that nothing has moved.

So, good one Hillhater. A nice solution for Kevo and also a good mod if you want make the drive a little narrower.

Here are a few shots of my test mule. Note the Acrylic side plates and swing arms. Still going strong. Running an 85A KForce in this one. Its standing up to the abuse OK hut it does get hot if I am pushing it. Had it pulsing on its high temp safety during one of the tests today.

[Hillhater]

Anyone like to offer any feed back on this "sync problem ? .. 63-54 , 250kv motor , 5 cell lipo.
I have tried re-programming the ESC (Turnigy KF 100) with different combo's of :-
... timing, 5 - 18 deg,
... start normal , soft etc,
...PWM frequency 12 - 24 khz

I still get what i assume is "sync failure" at med speed under load ..( screeching sound and motor stops with throttle still on)
Any suggestions for a optimum working set up.. Timing, PWM freq' etc ?

[SanFranRider]

Great thread guys.

Could someone post the "instruction manual" PDF for us lurkers who haven't bought a KFDS yet.

Also: anyone using a evLogix's throttelizer? Would like to know how that works, what connects to what, and what type of throttle is being used. Does the throttelizer eliminate the possibility of "magic smoke" emanating from the motor if you power uphill at a partial throttle setting?

Thanks!!!

[MrBoots]

I'm sure Andy will chime in here shortly, but the EVLogix Throttelizer links up to your ESC and customize parameters like current limit, voltage cut-off and temperature sensors. You can use either a hall-effect sensor or a 5K (potentiometer) type throttle. I've been completely satisfied with my throttelizer so far - I was pulling massive amounts of current before with my e-crazyman controller because my motor routinely got hot enough to burn my hand.

Now that I'm running a Castle Creations ESC, the ESC itself has become the weak-point in terms of current load. Right now, the current limit is set to 80A which is completely safe for both motor and ESC and the Throttelizer shuts things down when my voltage drops below 15V so I don't discharge the LiPO's too low. Great device and completely worth the money.