Spinningmagnets' RC Friction-Drive Build-log

spinningmagnets

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This build is a copy of EVTodds drive http://endless-sphere.com/forums/viewtopic.php?f=28&t=9652&start=0, Over time, I have grown to love the design. I am now determined to build one for myself, and also perhaps to sell a couple to local college students. I am also a fan of Keplers friction-drive, and after the local Australian demand slows to an even flow, I may purchase one to see if there's a market for them here in central Kansas. I am grateful to many members here for their help, but I couldn't have made it this far without Todds help and encouragement.

Todd is a professional machinist, and he has the tools and skills to make a quality product, I am just some old guy with a simple tool capability at the moment. Todds drive is built around a discontinued EV-Warrior one-way roller, which can occasionally be found on EBAY, but the problem has been that I can't find any source for new units.

The EV-Warrior roller has a knurled skin for traction, and it is hardened steel so it should last years with no visible smoothing. It also has a one-way bearing that allows the roller to remain in contact with the tire, and that means that the roller doesn't add any drag when you are only pedaling, while also allowing the drive to engage by simply adding power. Other powered bike kits sometimes employ a clutch or a lever to lift the entire drive unit off of the tire.

Some of the larger metal parts can be purchased off the web at http://www.onlinemetals.com/merchant.cfm?step=2&id=60 , I have not tried them yet, as I recently found a local supplier of the basic material. Todd was able to use a 3" channel to keep his drive as compact as possible. I decided to use a 4" X 4" square Al tube with 1/4" thick walls that has been chopped to 4" long and sliced lengthwise to make a channel with 2" deep sidewalls. The only reason I chose this is, that it is readily available here in quantity, and affordably priced. It can also be sliced to provide a channel with walls as deep as 3-3/4" as an option.

Todd milled slots in his channel which creates sliding guides when the drive is drawn deeper into the tread during engagement. This also keeps the parts-count low and the design simple. I don't have that capability, so I am using 3 Al flat-bars to similate his guides. They have been glued in place to ensure proper alignment during the next operation, and then drilled + bolted. The 3 Al flat-bars are 1/4" thick, the middle one is one-inch wide, and the two on the sides are each 1-1/2" wide

It is not neccessary to cut an additional lip into the side bearing mount-holes, but by doing that, I am able to flush-mount the bearings, which allows them to be covered and retained by a simple flat plate. It also allows me to use a shaft pre-cut by the vendor to 4". After marking and drilling the pilot holes, I used the larger hole-saw to cut a 0.060" deep circular groove for the bearing lip, and then I used a slightly smaller diameter hole-saw to cut a through-hole. I don't know yet if these rough methods will be precise enough to provide acceptable alignment in order to avoid high RPM vibrations. I will know in about one month.

Custom shaft lengths are available for anyone who prefers to have the supplier cut them, but affordable pre-cut shafts are rapidly available from existing shelf stock. I used McMaster-Carr for a case-hardened steel shaft, 1/2" diameter. Other vendors will work, but the shaft surface must be hardened for the one-way freewheel bearing to work.

FD 001.JPG

FD 003.JPG
 
Post reserved for final performance results, and parts list...

Edit: for those who are happy with 21-MPH (33-kph) I am now recommending the 63-64-280kV motor using 6S (22V) with a 1.25" roller, actual performance soon to be seen...

The parts that will take the longest to arrive are the Hobby King RC components from China. I made a list of parts I like, and optional parts that are acceptable. Then I was careful to only order parts that were in stock. If there is a specific part you're set on using (thats temporarily out of stock), where you don't want to spec an optional component, make that part a separate order. That way, HK won't hold back the rest of the parts waiting several weeks for the shorted part to arrive before shipping everything.

After performance testing results, I may end up wishing I'd used a different component than some of these (edit: I have), but here's whats on its way from China to get me started...(the charger requires a power supply, they can usually be purchased locally with an input from house current, or, 12V-automobile socket for RC charging in the field, or both)

Tax and shipping costs are not listed, as they can vary widely depending on your location, Prices listed are in USD on the day I purchased items (subject to change)

MOTOR, Turnigy 63-64-280, 10mm shaft, additional skirt bearing, $44
http://www.hobbycity.com/hobbyking/store/uh_viewItem.asp?idProduct=2097

CONTROLLER (ESC), Turnigy 85A, 1S-6S, Built-in BEC to power 5V servo tester as a throttle. $37
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=10331

CAPACITORS, 50V 1000µF low ESR capacitors, Panasonic part # EEUFM1H102, Digikey stock # P12393-ND, $1.40each
http://endless-sphere.com/forums/viewtopic.php?f=28&t=20961&p=316135#p316135
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=P12393-ND

BATTERY, Turnigy 6S (22.2V), 30C, 5000mAh, $76
http://www.hobbyking.com/hobbyking/...Product_Name=Turnigy_5000mAh_6S_30C_Lipo_Pack

CHARGER, Turnigy 7A charger for 1S-6S, balances cells during charging, 10V-18V input, $33
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=11341
CHARGER (OPTIONAL) US supplier in Ohio, only 1.5A slow-charge, but simple interface.
http://www.batteryspace.com/smartcharger15afor222vli-ionpolymerrechargeablebatterypack.aspx

BATTERY VOLTAGE MONITOR, wireless, Constant read-out of all 6 individual cell voltages, Red LED lights when lowest cell hits 3.6V, $30
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=7215

THROTTLE (servo-tester being used as a throttle), $15
http://www.esky-heli.com/esky-esky-servo-adjuster-tester-ek20907-000504-p-1532.html
Optional servo-tester, $6
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=8296

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

SHAFT BEARINGS, 1/2" inside diameter, flanged edge, I use two of them, arrived in mailbox less than 5 days in an envelope, $7 each
http://www.vxb.com/page/bearings/PROD/Kit7578

FREEWHEEL CLUTCH-BEARING, I use two of them, they slide onto a 1/2" shaft, arrived in mailbox less than 5 days in an envelope, $10 each
http://www.vxb.com/page/bearings/PROD/Kit8658

SHAFT, 1/2" diameter, case-hardened, available off-the-shelf in one-inch increments, arrived in mailbox less than 5 days in an envelope, less than $10 ea
http://www.mcmaster.com/#catalog/116/1058/=8sk0ir
 
I too will be following this Spinningmagnets.
Limited facilities can never hold back a determined and constructive mind ! :lol:
PS.. I have used the "hole saw" technique for bearing pockets. A little Devcon or epoxy on the outer surface of the bearing during final assembly will give a solid seating ! ( but i bet you were already planning on that anyway :wink: )
 
Nice! I like the cutting the 4 x 4 in half for nice flat edges. I made the mistake of getting some structural C channel that didn't have 90 degree inside corners. :? Which didn't work too well when it come down to it.

It looks very stout, and brilliant styles with the holes saws. What kind of bikes will you be showcasing this on?
 
I paticularly like the list post I think more builders should opt for this method, A nice clear list of materials and components and where to buy. I was going to wish you the best of luck on the build but I dont think luck has a lot to do with it! So instead I'll wish you a clear and constructive mind when it comes to cobbling this lot together :wink:

Regards
Tom
 
spinningmagnets said:
Post reserved for final performance results, and parts list...

The parts that will take the longest to arrive are the Hobby King RC components from China. I made a list of parts I like, and optional parts that are acceptable. Then I was careful to only order parts that were in stock. If there is a specific part you're set on using (thats temporarily out of stock), where you don't want to spec an optional component, make that part a separate order. That way, HK won't hold back the rest of the parts waiting several weeks for the shorted part to arrive before shipping everything. After performance testing results, I may end up wishing I'd used a different component than some of these, but here's whats on its way from China to get me started...(the charger requires a power supply, they can usually be purchased locally with an input from house current, or, automobile socket for RC charging in the field, or both)

Tax and shipping costs are not listed, as they can vary widely depending on your location, Prices listed are in USD on the day I purchased items (subject to change)

MOTOR, HXT 63-54-250, 10mm shaft dia, $56
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=5144

CONTROLLER (ESC), Turnigy 85A, 1S-6S, Built-in BEC to power 5V servo tester as a throttle. $37
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=10331

BATTERY, Turnigy 6S (22.2V), 30C, 5000mAh, $76
http://www.hobbyking.com/hobbyking/...Product_Name=Turnigy_5000mAh_6S_30C_Lipo_Pack

CHARGER, Turnigy 7A charger for 1S-6S, balances cells during charging, 10V-18V input, $33
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=11341

BATTERY VOLTAGE MONITOR, wireless, Constant read-out of all 6 individual cell voltages, Red LED lights when lowest cell hits 3.6V, $30
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=7215

THROTTLE (servo-tester being used as a throttle), $15
http://www.esky-heli.com/esky-esky-servo-adjuster-tester-ek20907-000504-p-1532.html

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

SHAFT BEARINGS, 1/2" inside diameter, flanged edge, I use two of them, arrived in mailbox less than 5 days in an envelope, $7 each
http://www.vxb.com/page/bearings/PROD/Kit7578

FREEWHEEL CLUTCH-BEARING, I use two of them, they slide onto a 1/2" shaft, arrived in mailbox less than 5 days in an envelope, $10 each
http://www.vxb.com/page/bearings/PROD/Kit8658

SHAFT, 1/2" diameter, case-hardened, available off-the-shelf in one-inch increments, arrived in mailbox less than 5 days in an envelope, less than $10 ea
http://www.mcmaster.com/#catalog/116/1058/=8sk0ir

I think the selection looks solid.

The motor should be up to the task. Just hope you dont have sync issues like Hillhater.

ESC is a bit light on. The 100 is a better choice but out of stock. (The 20 I recently bought might have contributed :oops: ) That being said, I am hammering an 85 at the moment and doing all I can to smoke it. Bloody thing wont break :twisted: I have hit the high temp limit on it a few times though.

Battery will be strong. 30c perhaps overkill for the job but adds a bit of insurance.

Good move with the 7A charger.

Links to the one way bearings and harden shafts has gone straight to my favorites tool bar :)
 
EVTodd said:
Looks good. One little thing that jumped out while reading... Keep in mind that clutch bearings can't handle radial load. They need to be supported by other bearings or bushings.
Todd,

You can get the drawn cup roller type in clutch only or clutch bearings. The ones linked to above have a set of roller bearings either side of the clutch mech.
 
Miles said:
EVTodd said:
Looks good. One little thing that jumped out while reading... Keep in mind that clutch bearings can't handle radial load. They need to be supported by other bearings or bushings.
Todd,

You can get the drawn cup roller type in clutch only or clutch bearings. The ones linked to above have a set of roller bearings either side of the clutch mech.

Yup. Just wanted to make sure since he talked about using two clutch bearings. If the second one is there just to handle the power I would try one first. I´ve put well over 1000 on mine so far without any problems.

Also, clutch bearings work better if the supporting bearings/bushings have a little radial direction play in them. I´m pretty sure that´s why ev warrior used bronze bushings instead of roller bearings. I do, however, want to give roller bearings a shot since they would spin better than the bushings.
 
Thanks everyone for the kind words!

About a month ago, I made the decision I had to DO something instead of just read. I then read back through many, many posts, to clip paragraphs with useful info, and make a list of the RC build info. Grinhill, Dontsendbubbamail, EVTodd, Zibby, etc. (the builds from Matt, AJ, LFP, etc, are completely in another league!) I wanted to compile a list of what motors and ESCs were used, and what problems they encountered (the RC E-bike field is really still a new thing). I had to laugh when I read my old posts where I was completely UN-interested in making a friction-drive for myself.

Hillhater, the Devcon sounds like a good idea, thanks! I may end up trying that, and if so, I'll likely oil up the bearing and have the Devcon stick to the aluminum. I'm disappointed in the holesaw that cut the 0.060" deep bearing flange lip. All they had in that size was a China unit, and I was in too much of a hurry. The Milwaukee hole-saw that made the through-hole worked well. If interest in these grows, I'll get a precise carbide rotary cutter for the lip recess.

etard, I've seen the channel with inner curves in the corners. 'Might' be OK if the bearing is mounted flat on the outer side of the side-plates? PM me if you need a channel to continue what you're working on. I boxed up the parts that made my specialized MTB a longtail. Since its the nicest bike I have I'll use it to show the drive, its a hardtail similar to Todds. I also now have a junk bike the same size and shape that I'm not worried about being stolen (locked up outside the apartment).

Kepler, I'm very happy about how things are turning out for your drive! Since your (2-1/2" ?) motor shell is the roller, and my current roller is one-inch, your low-RPM amp-draw will be more of a concern that requires some thought and attention. Since you are surviving with an 85A ESC, I am 'fairly' confident it will work for this build with a good safety margin. I saw the posts with Hillhaters synch issues (especially since its the same motor as this build). I would give him some advice about the ESC, but...I once tried to fix some electronics with a sledgehammer, and it just made it worse.

Too many people from ES to thank...everyone here has been very patient, generous, and helpful to me, and I am grateful.
 
Todd! Thanks for posting, I know how busy you must've been recently. Your GF's drive is brilliant! bike frames have many different configurations, and it would seem a seat-post mount (Kepler + your first drive) requires a low top-bar on the frame.

A Kepler responder had a tall frame that required custom shimming to get the roller close enough to the tire. I only mention this, because your second drive is located by the rear brakes in an orientation that is much more common, allowing for a much wider application to many different frames (A factor I also noticed on Grinhills build).

How are you going to attach the motor to the shaft? If you need an ev warrior shaft with the notches in it let me know and I´ll send you one.

Thanks for the offer, but I feel I should be riding exactly what I will be selling...even though I still don't know how I'll attach the motor! The roller may change a lot too over the next month, but that should be an easy upgrade. If you begin making new rollers, count me in to buy two!

I completely forgot about the clutch-bearings needing radial support needles! I am lucky, in that I got the bearings you spec'd earlier (Thanks!), and my bearings have them (I just checked!) I noticed Snaths drive had only one row (but with a high-torque rating), instead of the 3 rows of needles in the bearing you spec'd (he added additional bearing support)...(edit: [bearing pics added] I will just have to try this out, and then upgrade if needed. It will be annoying if I have to add a bushing, we'll see...)

hfl1.jpg


file.php
 
Miles said:


I seem to get a lot of reactions like that from you, hmmm. Oh well.

I did re-read your post and see what you mean now though. And yes, this clutch bearing has roller bearings in it. But... And I need to find it so I´m not talking out of my ass but I recall seeing a spec sheet on that exact bearing (same one I use) that says to use supporting bearings with it. I could be wrong though.
 
Hi Todd,

They're usually just called roller clutches if they don't have support bearings.
Ref: http://www.timken.com/en-us/products/bearings/productlist/roller/needle/Pages/DrawnCupRoller.aspx
 
Miles,

For these RC motors with 10 mm shafts, will one of these roller clutches carry the full torque of the motor? It would be cool to use one on the motor shaft pressed inside the tire roller. Compact and solves the alignment issues.
 
You may need more than one... You can see the specifications here: http://medias.ina.de/medias/en!hp.ec/1_R*0*62_R;ajJJEGEELAb_#HFL

I prefer the self-contained CSK type but you need to fix them to the shaft (they don't do a 10mm version, though...)
 
spinningmagnets said:
I saw the posts with Hillhaters synch issues (especially since its the same motor as this build). I would give him some advice about the ESC, but...I once tried to fix some electronics with a sledgehammer, and it just made it worse......

Hey, i am open to any suggestions ! :? ( and i do have a sledgehammer ! :shock: ) :wink:
 
Hillhater, I am not joking when I say I am an RC noob, and also very weak on electronics. It has taken me several months of frequently reading for hours to develop a 'still foggy' opinion. Its sort-of like gravity. I still don't really understand how it works, but...I think I've figured out which way its going. There's an old saying that, "when you are trained to use a hammer, everything starts to look like a nail". I'm the guy with an entire collection of hammers...

It sounds impressive to some people when they find out I was on a nuclear-powered submarine...but if the reactor ever went out, we had a large 2-stroke diesel as a back-up (air-start, hand pump to accumulator, mechanical fuel injection). Guess which engine I ran?

I'm sure I will burn out one of these electronic widgets, but sometimes you have to stop reading, and just order a part to take a chance.
 
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