Spinningmagnets' RC Friction-Drive Build-log

Discussions related to motors other than hub motors.
This includes R/C motors, botttom bracket, roller and geared drives.

Re: Spinningmagnets' RC Friction-Drive Build-log

Postby spinningmagnets » Sat Mar 05, 2011 3:59 pm

Just figured out the Castle Creations USB data-link. It is free (if you buy a new ESC from a legitimate retailer) by using a product-code found inside the package ($24 if you don't have the new product code). The code wouldn't work at first, until I figured out that one of the code digits was a capital letter "OH" and the other was a number "Zero".

I downloaded the program from the Castle website. The Windows program-install wizard window made the installation easy, (although I had to right-click and select "install as administrator"). The Castle data program is easy to access and read. These runs were made on the factory default settings, but its nice to know I can change them now if I want.

The website lists the 8S (33V max) Phoenix ICE-75A as 75A continuous, and 130A temporary peak. I made eight back-to-back hard acceleration runs on a slight uphill using 24V of SLA with a 1.0" diameter roller and the 295-kV motor, 180-lb rider on fat 26" tires.

All the runs were 60A peak, 30A to maintain top speed on a slight uphill, and downhill amps were almost unreadable because they were so low.

Watts were peaking at 2000, temporary voltage sag during accel with 12aH of SLA was about 5V, no sag during cruise. Started with 27V and average volts logged were 24V.

It was a warm day, and the peak temperature logged was the the last run, it zigzagged up and down on each run with the average temp sloping up, and final internal ESC temp was 100F (no fan installed yet).

Voltage-ripple...Fortunately, I ordered the ICE line (8S/28V) instead of the ICE-Lite (6S/ 22V). They both come with power-input capacitors, but they are sized to help a model aircraft instead of a heavy E-bike. I was getting enough voltage ripple (4V-ish ?) that I need to install a couple low-ESR caps ($5), and the extra ESC voltage capability probably helped me avoid popping something inside the ESC.

Since I am powering a 1:26 friction-drive instead of an axle-drive, I had hoped to avoid adding caps, but...it is what it is. I purposefully did a couple runs at 1/4 throttle, to make it as bad as it could be (Thanks to Matt for his generous assitance and advice!)

I don't regret having bought the generic no-feature 120A ESC (it still works), because it allowed me to sort out the mechanical end of the drive without worrying if I would fry the ESC (only $40). It will work as a back-up, and it doesn't have sync-loss as long as I don't accelerate hard.

Since I live 1.5 miles from work on a flat commute, I will use 6S and the 1.25 roller on the prototype drive. I will continue to test the production drive at 10S (37V) using the Hobbywing-ESC and 1.0" roller because the area around the college has lots of small hills.

edit: I want to clarify that I am recommending 36V for hills because the college students overwhelmingly don't want to use LiPo. Kepler/Adrian have proven these drives can climb well on 6S (22V-24V), but there is a lot of heat, and they use a 100A ESC at a minimum.

Without the high C-rate of LiPo available, I would need a bigger/heavier battery of LiFePO4/LiMn to avoid voltage sag. 36V doesn't bog down as much on hills, and as a result, it doesn't draw as many amps to maintain a long climb. If you like LiPo, this drive climbs well on 6S, but I would add a fan and a temp-readout...
Last edited by spinningmagnets on Tue Mar 08, 2011 1:26 pm, edited 3 times in total.
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Re: Spinningmagnets' RC Friction-Drive Build-log

Postby adrian_sm » Sat Mar 05, 2011 4:44 pm

spinningmagnets wrote:Just figured out the Castle Creations USB data-link. It is free.

That's great news.



Voltage-ripple- Fortunately, I ordered the ICE line (8S/28V) instead of the ICE-Lite (6S/ 22V). They both come with power-input capacitors, but they are sized to help a model aircraft instead of a heavy E-bike. I was getting enough voltage ripple (4V-ish ?) that I need to install a couple low-ESR caps ($5), and the extra ESC voltage capability probably helped me avoid popping something inside the ESC.

what happened to the ripple voltage after the extra caps were added?

-Adrian
Build #1 ~28kg ~ 700w Avanti Hardtail Crystalyte 408, 48V10Ah Headway. ~5500 kms to date. (retired)
Build #2 ~30kg ~2000w Giant AC Dually Crystalyte 408, 48V10Ah Headway + 6s10Ah LiPo = 70V. ~15000 kms to date [SOLD]
Build #3 ~13kg ~2000w Commuter Booster <1kg Friction Drive in Beta testing (www.commuterbooster.com)
Build #??? ~21kg ~1500w Adrian's Bafang BPM Hardtail MTB Bafang BPM code12, 15s LiPo, ~40kph, ~30kms
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Re: Spinningmagnets' RC Friction-Drive Build-log

Postby spinningmagnets » Sat Mar 05, 2011 6:17 pm

what happened to the ripple voltage after the extra caps were added?


I havent added them yet. I was so excited to finally get real data, I posted right away. Since I will be accelerating gently, and will not be using 1/4-throttle on an uphill, I am not worried to use the ICE-75 for my flat-road commuting as it is. I have two caps left over from when I ordered some and added two low-ESR fatties to a Turnigy 85A. When rearengine wanted to buy a drive from me, he opted to buy the 85A I had, so I don't have any data on that, other than it ran fine for me, and rearengine says he's happy with its performance.

ESCandCAPS.jpg
ESCandCAPS.jpg (47.08 KiB) Viewed 1446 times


The Hobbywing 70A that I have used at 36V (of SLA, soon to be LiPo) was $85. If someone wanted an HV (18V-50V) Castle Creations ESC (from Ebay) the 60A can be found for $115 (the next-bigger 80A can be found for $170). If the 60A has a temporary peak amp capacity of over 100A, it should be adequate for a 1.25" roller or smaller if you have light hills (with added caps, of course, and perhaps a fan).

For hills, I feel that 36V performs much better, and when considering the higher-voltage ESCs, the 70A Hobbywing 50V-ESC is $30 cheaper than the 60A Castle Creations 50V-ESC. I will beat on the Hobbywing ESC like it's a rented mule, and if it survives I won't have to spec the Castle-Creations $115 ESC as the minimum. Although, I will always recommend the Castle Creations unit as the better option if funds allow.

I will take it easy on the voltage ripple until I get the extra caps on, and then I will retest under hard acceleration (also 1/4 throttle on an uphill) to see how much it improves. AJs postings have suggested that doubling the uF (while making sure the extra caps are low-ESR) should cut the ripple in half, and Matt has said its very important to keep the ripple under 5V (the lower the better). Here are my preferred low-ESR cap choices for voltages "up to" 6S (22V), 10S (37V) and 12S (44V) viewtopic.php?f=30&t=22194&start=15#p325273
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Re: Spinningmagnets' RC Friction-Drive Build-log

Postby rearengine » Sat Mar 12, 2011 4:54 pm

Yup... No problems at all with the 85amp ESC with the 2 caps.. I'm pretty much running the drive like I do my hub motor ... usualy all out or, not at all .. Should be even less worry with the one" roller ...

by the way I got the roller in the mail today.. thanks... I'll see how this works with the launch ramp, and report the out come ... Bill
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Re: Spinningmagnets' RC Friction-Drive Build-log

Postby rearengine » Mon Apr 18, 2011 2:35 pm

Hey Spinner ... Have you moved in , and working in your garage yet?
I just wanted to post and say the drive is working as planned , but I took the launch ramp off ... I found that when it wasen't eccelerating it would set on the ramp and spin, because i would still have the thottle wide open.. Ya follow? The one way roller has to be in contact all the time now :| .. 85 amp esc with caps is still going strong ..How is your drive working ? By the way did you get your 1" roller back ok?

Kepler! if your out there ... How did your launch ramp work out ? Adien's seems to work fine with out it... Happy Easter to all... Bill
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Re: Spinningmagnets' RC Friction-Drive Build-log

Postby spinningmagnets » Mon Apr 18, 2011 5:57 pm

Got the roller, thanks! I will be flying to Utah on Monday, and I will be driving a U-Haul truck back to Kansas. There are so many good deals on houses here, it shouldn't take long for me to finally have a garage of my own soon.

The drives have been working well for me. The 1.25 inch roller with 24V does 20-MPH on flat land, and the 1.0 inch roller on 36V climbs well.

The soft rubber tire with a round profile (good for cornering) noticeably wore a bit, but the roller had a small contact patch... and to be fair, I was really hammering the drive and breaking traction around 2000W. The flat-tread (wide contact patch) hard-rubber beach cruiser tire is showing no signs of wear.

The 40-grit sand-paper from a cloth-backed wet-dry belt is wearing well, I used the best two-sided carpet tape I could find, and I seal the trailing edge with a smear of JB-Weld epoxy (wrap with tape until dry). I still hope to buy/make some steel rollers in the future.

I added capacitors to the 3 ESCs, and I haven't fried one yet. The CC-ESC data-logged that I was drawing 60A peak on acceleration, and the smallest ESC I have is a 70A-continuous. The 63mm motors are perfect for this application, they only get warm under hard use, and cool off quickly during cruise. I am using the Exceed 295-kV motor the most. It seems to be a well-made unit, but...Its normally listed at around $145, and yet they have occasional sales for $45 (huh? why such a wide spread of price?).http://www.hobbypartz.com/mo1102brmo.html

I'm not satisfied with using a dial on the servo-tester as a throttle. I have one of Matts throttles, but I'm too busy to put it on right now, and I'm certain it will be great when I finally do.

I tried to find the least expensive options that would work well and be reliable under "college-student" duty. The final version has turned out to be more expensive than I hoped for, so...due to price, I doubt many of them will sell. For my summer project I want to use a de-spoked hub as a non-hub to drive a longtail cargo-bike (like John-in-CR).
http://endless-sphere.com/forums/viewtopic.php?f=6&t=26932&start=15#p389622

I may make a frame using methods similar to the Tino Sana wooden bike. I'd make a shape with a big battery triangle and plenty of space just where I need the hub. Only about 14" longer tail than a normal bike.
http://endless-sphere.com/forums/viewtopic.php?f=1&t=10697&start=0#p163929
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Re: Spinningmagnets' RC Friction-Drive Build-log

Postby Kepler » Tue Apr 19, 2011 6:47 am

rearengine wrote:
Kepler! if your out there ... How did your launch ramp work out ? Adien's seems to work fine with out it... Happy Easter to all... Bill


Launch ramp has been great. Works a treat. Originally I needed to set my drives up with a very slight motor to tire contact. It wouldn't cause any drag as such but the slight scrape was annoying. Now the motor gets set 2 or 3mm away from the tire so there is no contact at all. Even a slightly out of round tire or flexing seat post doesn't cause any contact. I think the button throttle suits the launch ramp approach also as its either on or off rather the bouncing between the ramp and tire pickup. I now use it on both the rear mount and the mid mount setup.
mini and midi drive mechanics.JPG
mini and midi drive mechanics.JPG (32.72 KiB) Viewed 1285 times


Adrian's setup is different to mine mainly because his is optimised around being a centre mount. He uses a spring to pre load the motor against gravity. My design is optimised for a rear mount and need the spring action get the motor completely off the tire as the movement is no longer aided by gravity. My centre mount doesn't use a spring at all. On this configuration, the launch ramp is even more important to achieving reliable motor pickup. Dampening is all achieved electronically now with the engagement and disengagement silky smooth.
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Re: Spinningmagnets' RC Friction-Drive Build-log

Postby dickselectrictoys » Thu Jun 07, 2012 7:22 am

spinningmagnets wrote:Friction-Drives
Volt / kV-speed chart
For available 63mm motor kV's
1.0" and 1.25" roller diameters


The kV that is listed for a motor, is the RPMs resulting per volt applied. Many factors affect the actual road RPMs in use. The weight of the bike, rider, and cargo is a major factor, and also wind resistance and system friction. In the past, many have found that reducing the kV number by 15% can be a useful (though approximate) way to arrive at a calculated speed which is close to the actual resulting road-speeds.

I have compiled this chart as a rough guide to selecting a motor kV and system voltage. The top number is a 1.0" diameter roller and the bottom number is a 1-1/4" roller. LiPo and LiMn cells have a nominal voltage of 3.7V (and 4.1V when fully charged). Six of them connected in Series (6S) creates a cell-string that will have a nominal voltage of 22.2V; When fully charged, the string will have a voltage that is closer to 24.6V

Edit: I still have the original chart, but it has proven to be off some. I have developed two drive systems that both operate at arount the federal speed limit for unlicensed mopeds, which is 20-MPH (of course, the federal limit does not apply in those states where a higher speed is allowed)

Both are using the Exceed 295-kV motor. For flat land I am using 24V of SLA and the 1.25" roller, and for hill climbing, I am using 37V of LiPo and the 1.0" Roller. For the hill-climber, I am also adding more capacitors and a heat-activated air-cooling fan.

If you chose to use 44V-48V, the available kVs of the 63mm motors would provide you with a very wide range of top-speeds, with the 295-kV providing an estimated 27-MPH.

thank you" finally someone who knows what their talking about & right to the T.
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Re: Spinningmagnets' RC Friction-Drive Build-log

Postby windtrader » Sun Sep 14, 2014 12:29 am

Great thread. Thanks SM.

After 3 years, what is the update on this design? The whole FD topic sort of went dead as I scoured ES for newer news, designs, reports, etc.

Once starting from the head of the thread, I understand why all the extra bolts. Looking at the picture at the link it was less intuitive of what was going on. And the one-way drive shaft is certainly not identifiable just from the picture.

What are the limits on this design? Has anyone posted 25, 30, 35+ mph? How much slippage?

What about durability?

I'm hoping EVTodd weighs in as he has a lot of time with this too.

Thanks
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Re: Spinningmagnets' RC Friction-Drive Build-log

Postby spinningmagnets » Sun Sep 14, 2014 12:49 am

If you try to use a round-profile tread on the tire (good for cornering), it will slip a lot, especially with the slightest bit of moisture picked up from the road (because of the small contact patch). Todd suggested that I switch to a fairly flat (square?) profile tread, often found in a selection of beach cruiser tires. Found a cheap one at a local WalMart, and the rubber composition turned out to be fairly hard, which I also preferred. It worked as Todd described, MUCH better traction (no slippage unless very wet)

The power limit is dependent on the traction of the roller against the tire tread. My Castle ESC logged 1,000W peaks with no slippage. On flat land I got 20-MPH with 22V using a 1.25-inch roller, and in hilly terrain it actually climbed quite well when using 37V on a one-inch roller, also providing approximately 20-MPH.

I calculated the components to provide 20-MPH because that is the legal limit, and I hoped to sell a handful to some of the local college students. Every one was too nervous about LiPo to buy, and cell-man at em3ev.com had not yet started selling high-current non-lipo cells.

I rode my friction drive to and from work for a single summer/fall when the weather was nice...winter came and I put it in storage. I am happy with its performance, but I like riding faster E-bikes now, so it is just collecting dust next to my workbench as a work of art. It was a fun project and I really enjoyed every minute of it.

I never tried any voltage above 10S LiPo (37V?) or any speed over 20-MPH.
Last edited by spinningmagnets on Sun Sep 14, 2014 9:35 am, edited 1 time in total. View post history.
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Re: Spinningmagnets' RC Friction-Drive Build-log

Postby windtrader » Fri Sep 19, 2014 12:38 am

Hi SM,
The 40-grit sand-paper from a cloth-backed wet-dry belt is wearing well, I used the best two-sided carpet tape I could find, and I seal the trailing edge with a smear of JB-Weld epoxy (wrap with tape until dry). I still hope to buy/make some steel rollers in the future.
Did you upgrade from the sandpaper or did it hold up well and provide sufficient friction? Would be great if it held and avoid having to upgrade it.

Did the drive shaft lift off the tire while coasting or did the clutch bearing reduce drag sufficiently that contact was not an issue?

Could you venture an estimate on the maximum movement of the drive shaft into the tire?

Thanks
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Re: Spinningmagnets' RC Friction-Drive Build-log

Postby spinningmagnets » Fri Sep 19, 2014 11:27 am

Did the drive shaft lift off the tire while coasting, or did the clutch bearing reduce drag sufficiently that contact was not an issue?


There are two features of this style of friction drive that reduces drag when you are pedaling with no power on. First, the drive slides up and down, so...when the power is on...the roller pulls itself deeper into the tread. As the roller is pulling itself into the tread, the entire drives slides towards the tire with the roller. When the power is off, the wheel spinning forward pushes the drive forward until it's barely touching.

The second thing that reduces drag is that the roller has one-way clutch bearings inside it. They "grab" when the motor is on, but when the motor is off...the roller freewheels along with the tire (the roller shell spins along with the tire, but the shaft and the motor do not spin).

The roller must have a small portion of the roller touching the tread at all times (so that when power is applied, the roller can be pulling itself into the tread). Gravity and the weight of the drive is what makes it rest against the tire. Anyone who is skeptical about how much drag is felt would be very surprised that you cannot tell when it is touching or not (it wouldn't be touching if the angle of the drive's mount is adjusted wrong).
Last edited by spinningmagnets on Fri Sep 19, 2014 1:00 pm, edited 1 time in total. View post history.
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Re: Spinningmagnets' RC Friction-Drive Build-log

Postby windtrader » Fri Sep 19, 2014 11:37 am

Thanks. It seemed from the ETodd video the drive shaft was constantly spinning but wanted to confirm. This also seems to resolve the problem some have with the power not engaging immediately while the wheel is turning.

Did the sandpaper hold up and get solid traction or did you upgrade?
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Re: Spinningmagnets' RC Friction-Drive Build-log

Postby spinningmagnets » Fri Sep 19, 2014 12:59 pm

The 40-grit wet-dry sandpaper worked very well, but I haven't ridden the friction drive since I put it aside last winter, so many other projects to play with...
Last edited by spinningmagnets on Fri Sep 19, 2014 12:59 pm, edited 1 time in total. View post history.
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