Spinningmagnets' RC Friction-Drive Build-log

[Hillhater]

Ahhh ! ... looks like just the tool for getting my teenage son out of bed in the mornings !

[spinningmagnets]

Managed to drill/tap some holes and gouge out two oval slots. I decided to use 5/16"-18 bolts. Its a coarse thread, and probably bigger than neccessary, but compared to 1/4" bolts, I am less likely to break a drill-bit or thread-tap. On the underside of the top-plate, I cut out two central depressions to act as grease reservoirs (completely un-neccessary). Waiting for parts from China....

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[spinningmagnets]

It appears that the industry standard for an "interference fit" to serve our low power levels seems to be about 0.002". The two one-way freewheeling-bearings I am using happened to have a 0.750" Outside Diameter (OD), and I was able to find some Aluminum tube in the pile with a 0.748" Inside Diameter (ID),...the actual measurements vary from piece to piece. (of course, de-burr the tube ID before you start...)

If you are certain you will never want to press out the bearings and re-use them on something else, I suppose you 'could' epoxy them in with JB/Devcon to prevent slippage (if your available tubing has an looser ID of 0.750"-0.752").

I placed the tube section in boiling water, and the heat expansion increased the ID 0.010", just enough to easily tap the tube over the bearings. Have a hammer handy before starting, the two pieces have their respective temperatures equalize fairly quick once contact is made.

A friend suggested that the friction tape for the tops of skateboards is possibly the toughest friction tape available, compared to the tape used for steps. I might try both over time...

MAKE CERTAIN to mark the tube and both bearings before you start, so that after insertion, they are all pointing the right way...

set the bearing on a flat and firm surface...

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one shaft, two bearings, and a tube...

FD_009.JPG (139.05 KiB) Viewed 715 times

[etard]

HAHA!! Very funny pic Spin. It looks like this is coming together quite nicely, taking your time is gonna pay off I feel.

Is that 2 one way bearings in the aluminum tube? No spacers on the outside like the EV Warrior roller?

[spinningmagnets]

Yes, it is just the two one-way clutch-bearings inside the tube. Just an experiment, I don't know yet how this will turn out. Tube in the pic is one-inch OD, I can order Al tube with the 0.750" ID and a 1-1/4" OD, but I will check with my local supplier this week first. If they carry it, that will be cheaper, faster, and easier for me than onlinemetals.com

[Hillhater]

Can i borrow your reference library / "firm flat surface" sometime !

I have just had a thought about your motor shaft to roller shaft coupling..
You can get those roller clutch bearings for a 10 mm shaft size ..
http://www.vxb.com/page/bearings/PROD/O ... gs/Kit8644
.. so, you could simply replace the complete motor shaft with a longer one to go straight through the roller as well as the motor stator.
. ( as discussed else ware, changing the motor shaft is simple )
..Or to use the brgs you already have, get a shop to make you a precision 1/2" stepped to 10mm shaft, not as cheap but not a big job for a CNC lathe shop.

Just a thought , it would eliminate the cost , complexity, and reliability of a coupling.

Also, found this .. 10mm -12mm coupling

[spinningmagnets]

You can borrow any book of mine you need, Hillhater. Including my 12-volume set of "Understanding a Womans Mind" (sadly, its in Latin...and the author killed himself before finishing the final 24 volumes). Thanks for the links, more options are a good thing to add to the list of possibilities. I think it 'may' actually be a good thing to have a small amount of 'slop' in the joint (rather than a single long solid shaft between motor/roller). But, that sounds like a worthwhile future experiment...

The method I'm trying has several other options discussed in this thread: http://endless-sphere.com/forums/viewtopic.php?f=28&t=21380&start=15#p312809

I managed to get my shaft end-slot cutter running. Its just an experiment, but so far, I'm pleased with how its turned out. I stacked four of the 3" diameter cut-off abrasive wheels onto a 3/8" all-thread shaft, and I drive it with a cordless drill. Used some scrap I had laying around, with two cheap flanged bearings from the hardware store.

edit; I FINALLY remembered where I had seen this before! Grinhill did this on his Mk2-Build
http://endless-sphere.com/forums/viewtopic.php?f=28&t=10635#p162911

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[gtadmin]

... Including my 12-volume set of "Understanding a Womans Mind" (sadly, its in Latin...

and in an ink invisible to the male eye ...

[Hillhater]

... Including my 12-volume set of "Understanding a Womans Mind" (sadly, its in Latin...

and in an ink invisible to the male eye ...

Yes , i am sure i have seen that in the "Fiction" section of the bookstore !

Nice work on that shaft joint SM" 1 .. I love improvisation !

[spinningmagnets]

Motor arrived in 11 days from Hobby King. Based on a new-to-you test procedure I found on an RC site, I threw together a cheap test stand to be my third hand. Its possible to fry a motor or ESC when you are new to this game (as I am).
http://www.wattflyer.com/forums/showthread.php?t=35216
http://aircraft-world.com/prod_datasheets/hp/motorguide/motorwiring.htm
http://www.rcgroups.com/forums/showthread.php?t=240993

Todd originally used 36V cordless-drill packs (available from DeWalt and Milwaukee), and I felt that those would appeal to non-technical college students. Also, using higher volts can sometimes mean you need fewer heat-producing amps to do the job. I wanted to use the 28V packs, which were smaller, cheaper, and actually have a higher discharge capacity (the C-rate, meaning Current). Also, both Milwaukee and DeWalt have made long-term committments to ensure continued production of their 28V line.

Just as I was about to buy several barely-used packs from a fellow ES member, I got my hours at work cut. More time on my hands (good) but less money for parts (bad). I have settled on the 6S LiPo packs (22V-24V) for the lower price, and also to get some hands-on experience with LiPo, as I believe RC and LiPo will soon take over a large share of the E-bike market.

I've been told by a friend I will likely only get 13-MPH (21-kph) from a 250-kV motor-winding at 22V with a 1" diameter roller on a 26" wheel (I guess we'll see, should have good hill-climbing ability and low ESC heat, with no synch issues, and should start from a dead stop easily on heavy cargo bikes). I plan to also try an 1-1/4" roller, different kVs and different voltages, both on hills and the flats. I hope to log amp-draw for each. However, if I had started out with a bigger motor and higher kV, I would have always wondered about the smallest motor I considered as acceptable for my goals (63mm diameter, 10mm shaft).

"should" get 20-MPH from a 280-kV, using 6S (22V-24V) with 1-1/4" roller...

I guess I can now retire the stunt-double, which is a 5-oz can of vienna sausage (Visualize an old homeless-looking guy with calipers, wandering through a store measuring cans). Kaiser Wilhelm once said, if you like laws and sausages, don't ask how either of them are made.

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Edit: added a list of other possible motors...The first # is the motor diameter in mm, the second # is the length in mm (the internal motor section, the outer motor body is longer), and the third # is the kV (RPMs per volt applied). The black motors are advertised as having better bearings. A higher kV will have a higher top speed while using the same volts, but it will also have more motor/ESC heat at low RPMs.

The first section has 8mm diameter shafts (I prefer to work with the larger 10mm when possible).

$49 63-59-259 silver
http://www.hobbycity.com/hobbycity/stor ... oduct=4572

$40 50-65-270 black
http://www.hobbycity.com/hobbyking/stor ... oduct=7709

$30 50-65-270 gold
http://www.hobbycity.com/hobbyking/stor ... oduct=5204

$24 50-65-320 gold
http://www.hobbycity.com/hobbyking/stor ... oduct=4913

$56 63-45-330 silver
http://hobbyking.com/hobbyking/store/uh ... oduct=2136

$30 50-65-350 gold
http://www.hobbycity.com/hobbyking/stor ... oduct=2101

$40 50-65-380 black
http://www.hobbycity.com/hobbyking/stor ... oduct=7070

$30 50-55-400 gold
http://www.hobbycity.com/hobbyking/stor ... oduct=2102

$30 50-65-400 gold
http://hobbyking.com/hobbyking/store/uh ... oduct=4914

$190 50-62-400
http://www.scorpionsystem.com/catalog/m ... -4035-400/


XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

10mm shafts

$60 63-74-170 black
http://www.hobbycity.com/hobbyking/stor ... oduct=7870

$60 63-74-200 gold (has additional skirt bearing)
http://www.hobbycity.com/hobbyking/stor ... oduct=3890

$45 63-64-230 blue
http://www.hobbycity.com/hobbyking/stor ... oduct=4188

$60 63-64-230 black
http://www.hobbycity.com/hobbyking/stor ... oduct=7710

$50 63-64-245 blue
http://www.hobbypartz.com/mo1602brmo.html

$56 63-54-250 gold (has additional skirt bearing)
http://www.hobbycity.com/hobbyking/stor ... oduct=5144

$44 63-64-280 gold (has additional skirt bearing)
http://www.hobbycity.com/hobbyking/stor ... oduct=2097

$45 63-54-295 blue
http://www.hobbypartz.com/mo1102brmo.html

[Hillhater]

I've been told by a friend I will likely only get 15-MPH (24-kph) from a 250-kV motor-winding at 22V with a 1" diameter roller on a 26" wheel (I guess we'll see).

I have the same motor as you ( 63-54-250 gold) .. but direct friction drive using 5s (18.5v).
Real Results from running it with the bike on a trainer stand give me a max ,no load, speed of 57kph and a "loaded" (simulating flat road ?) speed of 44kph.

So, you should have a voltage increase of 20%, but a roller diameter reduction of 60% ...
so your no load speed should be... 57kph * 1.2 * 0.4 = 27.4 kph
and a "flat road speed of.... 44kph * 1.2 * 0.4 = 21.1 kph

... but boy, you should be able to climb walls with that !

And obviously your road speed would increase in direct proportion to your roller diameter ( Just wrap a few more turns of grip tape on there ! )

Another random thought...
have you ever worked with expanding mandrels or rolls ? ... i can imagine an expanding drive roller controlled by centrifugal force !!

[spinningmagnets]

Thanks for the info, hillhater. I used 4" square tubing to cut out the channel I am using, so its possible to cut the side legs to a max of 4" long instead of the 2" I am currently using. It is then possible to install a roller that is 4" in diameter, and I have found a solid hard plastic wheel that is 3" in diameter with a shaft-hole of 1/2" (among others), along with an aluminum flange that can clamp the 1/2" shaft to the side of the roller. So the 1/2" shaft provide many options from industrial parts suppliers.

I am nervous about buying one of the 50mm diameter motors (with an 8mm shaft), as it has been tricky enough (for a non-machinist with no garage) to mate the 10mm with the 1/2" (0.394" to 0.500"). That being said, the kV's of the smaller motors will provide a higher top-speed while using a simple 6S LiPo brick-sized battery.

Going to a higher voltage to get higher top-speeds from the 10mm shaft-motors changes everything too. 8S (28V), 10S (36V), and 12S (44V) are a completely different ballgame as it concerns motor kV selection. A higher voltage means specifying a more expensive charger and MUCH more expensive ESC. I've been told by several enthusiasts, never go cheap on the charger, as LiPo is the type of battery chemistry that may catch on fire if overcharged. I will also use a separate power-timer, to cut power to the charger a few minutes after the battery is typically at a full charge after having just hit the battery low warning light.

If a specific motor turns out to be a clear winner with customers, I 'may' learn how to install halls (I've saved the posts and links) so there would be a 6-FET sensored-controller option (for 36V and 48V), but if that even happens at all, its down the road a ways.

I've got the parts on their way for a 1.25" roller since many here are reporting good service with just the friction-tape. As an experiment, the 1.0" roller may have a steel sleeve clamped over it (who knows, if that will even work?). If the math ends up looking good for a 1.5" Al roller using friction-tape, I can make brass bushings to fit the 0.750-OD clutch-bearings to the appropriately-sized tubing, but I'd rather avoid that if I can. One possible option is slipping a 1.5" tube over the 1.25" tube (if they are snug enough, looks possible) plus glue and/or grub-screws...

PS, I really like the clear housing you made for your motor! My new avatar is my sons computer with a clear housing and blinky lights inside.

Does anybody have a running 8mm-shaft motor (any kV) that they don't care for much? After I fiddle with various 8mm-shaft coupling arrangements, it may not be sell-able to anyone, as I may cut the shaft shorter and grind flats onto its sides.

[spinningmagnets]

Just ordered another set of bearings for my sons kit, when ordering from VXB, they often ask if you would like to add a 6" digital caliper for $10 plus shipping ($5 extra?, so $15-ish total). I have the same model, but as a 4" long, which I find to be more "pocket-able". If you don't have a caliper yet, it can be useful. It reads out inch or mm at the push of a button.

I have often made a black felt marker dot on aluminum, then gently scratched an X onto it in a precise spot with the steel caliper tips (a professinal machinist would cringe, but the caliper tips are just fine). I place a dent into the center of the X with a sharp pokey-device made for that ("sharp pokey device" is a technical term I learned from an engineer in the aerospace industry), and the dent keeps the small pilot drill bit from wandering.

I use a 3/16" pilot, as its the smallest one I found with three flats on the shank. Drill slow, stop to clear shavings often, and use lubricant (insert joke here). Once the pilot hole is complete, a larger bit can finish the job in the precise spot you wanted a large hole.

[spinningmagnets]

Recieved a link to an electric rear-wheel friction-drive with separate motor and roller from 1899 by John Schnepf, (So I'm only 111 years late to the game. Thanks for the pic, Roni). I notice it uses an off-the-shelf concave pulley wheel as the roller (recently suggested by paultrafalgar viewtopic.php?f=28&t=9652&start=90#p183070).

I suspect the dotted blank sections would contain two small DC motors.

[recumpence]

Found an electric rear-wheel friction-drive with separate motor and roller from 1899 by John Schnepf, (So I'm only 111 years late to the game. Thanks for the pic, Roni). I notice it uses an off-the-shelf concave pulley wheel as the roller (recently suggested by paultrafalgar http://endless-sphere.com/forums/viewto ... 90#p183070).

There is one issue with using a curved roller like that;

You will have significant scrub because the roller and wheel have reversed radiuses contacting each other.

It is shockingly similar to our modern systems, though.

Matt

[spinningmagnets]

It is shockingly similar to our modern systems

Yes! that was my first thought, too. I thoroughly enjoyed Miles' post about old bicycle inventions, and there being nothing new. I have been told that most cars before the 1920's were purchased for cash, rather than making payments. It was suggested that the financing was one of several reasons the bare-bones Model-T (with ultra-low price) was so successful at the time.

Its easy to forget that before WW-one (1914-17), a bicycle was a major purchase, and a patent for a desirable bike invention had a very wide market. The penny-farthings with the giant front wheel (long spokes for 'some' suspension on hard roads) were prone to a 'face-plant' crash, and I'm told the Starley "safety bicycle" of 1885 was a very big hit (in spite of the really weak front "spoon" brake). (edit, take note that the entire frame flexes as added supension)

Starley_Bicycle_1885.gif (53.99 KiB) Viewed 1475 times

[Hillhater]

I have often made a black felt marker dot on aluminum, then gently scratched an X onto it in a precise spot with the steel caliper tips (a professinal machinist would cringe, but the caliper tips are just fine). I place a dent into the center of the X with a sharp pokey-device made for that ("sharp pokey device" is a technical term I learned from an engineer in the aerospace industry), and the dent keeps the small pilot drill bit from wandering.

I use a 3/16" pilot, as its the smallest one I found with three flats on the shank. Drill slow, stop to clear shavings often, and use lubricant (insert joke here). Once the pilot hole is complete, a larger bit can finish the job in the precise spot you wanted a large hole.

S'M speak ............... Vs .................. Engineer's Speak
black felt marker dot .............. = Engineers "Marking Blue."
scratched an X onto it in a precise spot with the steel caliper tips... = Engineers "Scriber"
place a dent into the center of the X........ = center location mark
a sharp pokey-device made for that........ = a "Centre Punch"

Why do you use a pilot drill with flats on the shank ??
..you can buy professional "Centre Drills" with 1/4" shank and 1/8" pilot tip specifically made for precision centre placement, and providing a "lead" for the larger drill.
The key to precise, clean, round, (?) holes is to use a correctly precision sharpened drill bit.
( drills sharpened by rubbing them by hand on a kerb stone , dont make nice holes ! )

[Hillhater]

and I'm told the Starley "safety bicycle" of 1885 was a very big hit (in spite of the really weak front "spoon" brake).

My first bike ( waaaaaay back !) had "Stirrup" brakes , on the inside of the rim, worked by solid rods !
Not too hot..as i recall.... ( you get a lot of muck on the inside of bike rims)


SM... I assume you would be considering "re-profiling" that 3" roller ! ... a 3" drive would result in 60+kph, loaded ... if it ever got going !
I am currently pondering the option of sensored motors and controllers to overcome this "sync" issue that is bugging me.
The issue i see is that even if you (or I) succeeded in fixing the halls in the motors, we are then seriously limited on controller options for our "low" voltage systems.
Most sensored controllers commercially available, seem to be for 24v and up, and have relatively low (40A) current capacity which is not really suitable for our drives if we want to use 1kW or more. It appears we would have to use customised or purpose built controllers ..and they dont have the best reliability record either. It is a case of "out of the frying pan, into the fire !
I was about to bite the bullet and try one of the infamous Castle ESC's , to see if it solves the sync issue, before i get all "cacky" with epoxy and halls !
.......but i just caught up with Oatnet's Kepler build using the CC ESC, and he has a similar sync issue too !

PS.. re those 8mm motor shafts... remember these shafts can be swapped out easily with similar sized ground shafting.. no permanent damage to the motor.

[spinningmagnets]

I've always liked the antique brake linkages that used rods instead of cables, but Ive never before seen brake pads that rubbed on that particular part of the rim!

Concerning the 3" wheel as a roller, there is a 170-kV motor on the list, I don't know what speed that would come out to on 5S or 6S. Just another option on my long list of possibles. Lets see...170-kV at 18V and 22V, equals 3060 and 3740-RPMs, deduct 15% for reduced RPMs under actual loads (X 0.85) = 2600 and 3180 RPMs, and on a 3" wheel (see chart in resources stickie) = 24 and 27-MPH (38 and 43-kph).

That was a useful exercise, but I fear the 3" wheel would have excessive heat at low RPMs and high throttle. When given a choice, I would lean towards higher voltages in a higher kV of motor with a smaller roller...In my current set-up (22V in a 250-kV motor) I believe I will need a 1.5" roller to get 21-MPH

I had a 1/8" pilot drill bit of quality steel with a hex shank (with many miles on it) that I bought because my cordless drill has a weak chuck, and round-shank bits (especially small diameter) tend to slip quite a bit. The pilot bit decided to break just when I needed it most. Being an ex-sailor and an ex-truck driver, I took that moment to cast a few aspersions on the drill bits parents, and also its personal character. When buying a new pilot bit, the smallest I could find nearby was a 3/16 with 3 flats on the shank, but it works.

[Solcar]

I am surprised that they still use those spoon brakes in some areas. Has anyone else noticed them in oriental photographs of street traffic?

It is shockingly similar to our modern systems

Yes! that was my first thought, too. I thoroughly enjoyed Miles' post about old bicycle inventions, and there being nothing new. I have been told that most cars before the 1920's were purchased for cash, rather than making payments. It was suggested that the financing was one of several reasons the bare-bones Model-T (with ultra-low price) was so successful at the time.

Its easy to forget that before WW-one (1914-17), a bicycle was a major purchase, and a patent for a desirable bike invention had a very wide market. The penny-farthings with the giant front wheel (long spokes for 'some' suspension on hard roads) were prone to a 'face-plant' crash, and I'm told the Starley "safety bicycle" of 1885 was a very big hit (in spite of the really weak front "spoon" brake). (edit, take note that the entire frame flexes as added supension)

Starley_Bicycle_1885.gif

[spinningmagnets]

StemMount.jpg (85.36 KiB) Viewed 1123 times

http://endless-sphere.com/forums/viewtopic.php?f=28&t=22245
http://www.niagaracycle.com/index.php?cPath=129&sort=2a&page=2
http://www.jensonusa.com/store/sub/147-Stems.aspx

I have been very impressed with Hillhaters use of a bikes handlebar stem as a mount option, and I am trying to figure out how hard/easy it would be. AJ pointed out that stems are available with an adjustable angle, and that solves several problems for me. Niagra bicycle parts has 38 pages of stem selections, so I am collating the adjustable-angle stem options available to me.

The vertical post that inserts into the steer-tube of a bike is the quill (like the quill of a feather-pen being dipped in ink). The length from the center of the quill-clamp to the center of the handlebar-clamp is often referred to as the reach.

The quill-clamp inside-diameters (ID) are either not listed, or are listed as 1-1/8" (1.125", 28.57mm)

Bar-clamp ID's listed are in millimeters and are
22.2, 25.4, 26.0, 31.8

Reach are also in mm, and are
80, 90, 95, 100, 105, 110, 120, 125

If you wanted to use a fixed stem, just like Hillhater, they also list the "rise", which can be zero (90-degrees in relation to the quill) up to a steep angle. Fixed stems also present an intriguing option. The bar-clamp end often has a removable cap, which might allow the stem to be attached to a bike-frame seat-tube, rather than the removable seat-post (though the biggest bar-clamp ID listed is 31.8mm).

Some stems for downhill (DH), Dirt-Jumper (DJ), and BMX bikes are short and quite strong, and many of them have zero rise, such as the pic below.



There are various adapter-sleeves called seat-post shims, split-bushings, bore-reducers, etc. They may allow a certain stem to be used with a particular diameter of tubing. I have made these in the past, and my favorite materials are a section of brass plumbing pipe, aluminum crutch-tube, or electrical conduit.

The original diameter of the pipe is not so important as the wall-thickness. You can spin the pipe by some method and file/sand the OD until you achieve the proper wall-thickness, then chop to length, and slice one side to allow it to spread out to a useable diameter. I have also cut the pipe into two half-sections when appropriate.

http://problemsolversbike.com/index.php/products/seatpost_shims
http://www.niagaracycle.com/index.php?cPath=108_188

TwoPartBushing.jpg (7.05 KiB) Viewed 1118 times

[Kepler]

Good info Spin. Great being able to get high quality parts off the shelf. I really like this idea of using an adjustable handle bar stem however, I come across so many bikes with larger 31.8mm seatpost. Still, for those with 27.2mm seat posts, this is very tidy way of doing the job.

[spinningmagnets]

Thanks for the kind words! Are you as busy as I mentioned in several posts, that I'd thought you would be?

Good point on the seat-post diameters (thanks for reminding me!), the cheapest bikes often have a 1.0" diameter post, and two of my bikes have the 27.2mm variety. E-commuters seem to eventually end up with a mountain bike to affordably get a front disc brake, fat tires, and suspension for the potholes/curbs we are forced to pass over. Bigger diameter posts seem to be the trend for upscale MTBs...

If a stem-mount looks like a solution for a problematic application, a seat-post shim can be used to insert a smaller diameter seat-post into a bigger seat-tube. Here's one list of seat-post shims that are only $7, and should cover most adaptations.

http://endless-sphere.com/forums/viewtopic.php?f=28&t=21365&start=45#p318293

[Kepler]

Very busy at the moment. Re designing to make manufacture more afordable and basically lower the parts count. Also looking at some additions to the drive (avatar is a bit of a sneak preview ) Interface refinement is the biggest focus at the moment though as I firmly believe this the key to bringing RC friction drives to the people.

[spinningmagnets]

HA! Just noticed the new avatar before I read what you wrote! I should have known that there was no dust collecting on your R&D bench! I suppose you can sleep when you're dead!

Between the two-speed Kepler-drive, and the throttle interface, I believe you will have solved the remaining problems of adapting RC motors to E-bikes for the masses (since both of those solutions will reduce the peak amps the ESC sees). The interface in particular is something I anticipate to be a huge seller for you, as it sounds like it will be useful to just about any RC application. The other option for designers who crave a medium-power RC-motor is to add hall-sensors and use a larger 6-FET Infineon controller, so your gadget is a very easy decision.

Matt's recommended combination (Astro 3220 motor with Castle Creations HV160A ESC) is truly wonderful, but at $700 its beyond my budget right now.

Jeremy Harris has designed a compact and affordable throttle-signal-translator which will find its niche, but it doesn't have the wide range of solutions and features that you have described for your unit. I would say "best of luck" but I don't think you need any more luck, you are clearly on your way by virtue of your research, wise choices, and hard work!