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 1171 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 966 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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