Commuter Booster - <1kg Friction Drive

Discussions related to motors other than hub motors.
This includes R/C motors, botttom bracket, roller and geared drives.
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def215   10 kW

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Re: Commuter Booster - <1kg Friction Drive

Post by def215 » Jan 18 2011 1:32pm

i forgot about the floods also. i remember kim posting in general discussion about that.

snow can be fun at times, but not with a friction-drive :cry:

the remote shunt has to be the best mod ive found, although i have a different watt meter to work with

kepler,

i like the sound of that interface. seems like it can make this rc stuff easier than it really is :mrgreen: right now for my FD i have a diy 555-timer servo tester, a battery to power it, the esc motor and battery. that interface can really simplify it down.
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Re: Commuter Booster - <1kg Friction Drive

Post by adrian_sm » Jan 18 2011 2:31pm

gfulton wrote:Hi adrian_sm and others,

I've just been lurking here off and on the last couple of years. I have a question about the engagement of the drive to the wheel... is it always touching the rear wheel via spring force... but just barely? Once the throttle is engaged and power is put to the motor does it 'climb' the rear wheel until hitting a deadstop? From reading the previous posts I wasn't quite sure how you had it rigged.

The ESC, motor, servo-tester and throttle setup is all clear, I have everything going, even a thumb throttle... I just have to understand the mechanics of the mount. Thanks.

Thanks.
Wow. Long time lurker indeed. Glad you dropped by my little thread. :D

How it Works:
Motor Engagement:
My drive uses a spring to counter-balance the motor weight such that it will sit just clear of the tyre, with the lower deadstop adjusted to this position as well. This stops the motor from pivoting further away from the tyre than necessary.
Once the throttle is engaged the reaction to the start up torue of the motor actually pivots the swing arm, and lifts the motor into contact with the tyre. Once it makes contact with the tyre it then relies on the motor gripping the tyre to further engage.
How much it engages is then dictated by three things:
1) the geometry, specifically how much interference there is between the arc the motor swings through and the tyre.
2) tyre pressure & size, this sets how much force the tyre reacts with, and over what area.
3) the upper dead-stop, this is used to limit how much the pivot arm rotates, and how far the motor interferes with the tyre.

Friction:
Friction is how the torque of the motor is transferred to the tyre, rather than using a belt or chain reduction. The main advantages of this system are:
- it can totally disengage for zero additional drag when not in use
- good effect reduction ratio
- simplicity

But you are at the mercy of the friction coefficient between motor and tyre.
The aim is to have a high coefficient of friction, as this reduces the force with which the drive needs to engage into the tyre for a given torque. The real benefit here is in efficiency. The more you engage into the tyre, the more energy you waste in deflecting the tyre structure. Distorting the tyre less will reduce that wasted energy, and most likely have a positive impact on tyre life as well, as the tyre surface in the contact region is not trying to move tangentially, or axially relative to the contacting friction roller (the motor can in my case) as much. Set-up right the friction roller engagement should not be significantly worse for tyre wear than the usual tyre to road surface wear.

The trick really is to make sure it doesn't slip, as you lose power transfer and start eating your tyre up. I don't quite have good guidelines for this process yet, as it is a balance between efficiency and robustness. The issue being things can change once set-up. Maybe your tyre pressure goes down, resulting in a lower reaction force, and reduced max torque before slipping occurs. Or it rains, and this reduces the coefficient of friction, again limiting the amount of power you can lay down. This is one of the reasons I went with an upper dead-stop that limits the amount of engagement into the tyre, as it gives the user the potential to quickly adjust for more engagement for just these scenarios, without affecting the other set-up parameters.

Max Power:
These friction drives are not really suited for high power set-ups for a couple of reasons.
1) you would need very aggressive engagement into the tyre to transfer the torque, leading to more wasted energy. Making other gearing options attractive.
2) the small motor sizes just can't handle a lot of waste heat. One of the reasons to only use them above a walking pace, as motor efficiency is pretty crappy below this.
Friction drives are definitely more suited to the light-weight assist type market, than the all out speed/torque beast user. Having said that can work well for over 1kw, which is a very usable amount of power.

Variable Engagement:
Finally the geometry of this, and other friction drives on the forum, allow for automatically adjusted variable engagement. Essentially the drive will engage less when low torque is applied, improving efficiency. Then when you give it more throttle and demand more torque, the drive will engage more allowing for greater torque transfer.

I haven't studied this properly for my geometry to verify it works enough to make a difference, but it sure sounds nice. :lol:



That probably covers a few things you already know, but hopefuly it answers your questions.

So have you started building something yet. Would love to see what you have come up with. I like the two speed set-up you mentioned in your first post. It might help with overheating of motors when lugging up hills. But I guess I would just be tempted to go for a bigger motor with more thermal mass, or limit power.

- 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
Build #??? ~21kg ~1500w Adrian's Bafang BPM Hardtail MTB Bafang BPM code12, 15s LiPo, ~40kph, ~30kms

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Re: Commuter Booster - <1kg Friction Drive

Post by hillzofvalp » Jan 18 2011 2:47pm

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Re: Commuter Booster - <1kg Friction Drive

Post by Kepler » Jan 18 2011 3:14pm

adrian_sm wrote:

How it Works:

- Adrian
Wow Adrian, that is a great explanation of how the latest batch of friction drives work. Might get you to write my manuals in the future :)
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Re: Commuter Booster - <1kg Friction Drive

Post by Kepler » Jan 18 2011 3:48pm

def215 wrote: kepler,

i like the sound of that interface. seems like it can make this rc stuff easier than it really is :mrgreen: right now for my FD i have a diy 555-timer servo tester, a battery to power it, the esc motor and battery. that interface can really simplify it down.
Not sure if the interface will make it simpler but it will make any friction drive a lot more user friendly :)
The interface is designed to solve 2 major issues associated with RC style friction drives.

1) Minimum start speed.
The interface will not allow the drive to start until a minimum speed is reached. This protects the motor by reducing loss of sync events which are worst at startup. It also protects the tire as applying lots of torque at start up very easily slip on the tire. This start up slip tends to be on a concentrated section of tire and as such does a lot more damage then slip at higher speeds. This is especially important with the abrasives we now use to improve our friction coefficient.
At the moment, minimum interface startup speed is around 8 kph. This is as low as we can currently make due to physical limitations of measuring wheel speed via a reed switch.

2)Protection of the ESC at low speeds.
One of the major limitations of RC style ESCs is that they wont survive low throttle settings under high load. They will however tolerate low throttle settings with moderate load.
The interface gets around this by assigning a max Watt setting to a given wheel speed. At low speeds, the interface will map a lower Watt setting. As the wheel speed increases, the max Watt setting keeps on rising and subsequently allows you go faster. This current limiting at low wheel speed also significantly reduces sync loss issues.
A negative aspect to this control strategy is that low speed acceleration is quite mild. At the slowest mapped speed, the interface limits current to around 200W. However,this quickly rises as the wheel speed increases.
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Lightest true ebike on the planet: ON ROAD viewtopic.php?f=6&t=74269
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Re: Commuter Booster - <1kg Friction Drive

Post by adrian_sm » Jan 18 2011 4:07pm

Kepler wrote:At the moment, minimum interface startup speed is around 8 kph. This is as low as we can currently make due to physical limitations of measuring wheel speed via a reed switch.
Two magnets on the wheel, 180 degrees apart, might help?
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
Build #??? ~21kg ~1500w Adrian's Bafang BPM Hardtail MTB Bafang BPM code12, 15s LiPo, ~40kph, ~30kms

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Re: Commuter Booster - <1kg Friction Drive

Post by adrian_sm » Jan 18 2011 4:17pm

Kepler wrote:2)Protection of the ESC at low speeds.
One of the major limitations of RC style ESCs is that they wont survive low throttle settings under high load. They will however tolerate low throttle settings with moderate load.
Is it worth thinking about a baby 6fet Ebike controller? These are still pretty small, can be modded for our voltages, and to override the current spike issues with these motors. Would have current limitting/programming built in. We could mount externals hall sensors on our swing arms....

I am sure there are some downsides but seems to be an option. What am I missing?

- 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
Build #??? ~21kg ~1500w Adrian's Bafang BPM Hardtail MTB Bafang BPM code12, 15s LiPo, ~40kph, ~30kms

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Re: Commuter Booster - <1kg Friction Drive

Post by Hillhater » Jan 18 2011 5:36pm

adrian_sm wrote: Is it worth thinking about a baby 6fet Ebike controller? These are still pretty small, can be modded for our voltages, and to override the current spike issues with these motors. Would have current limitting/programming built in. We could mount externals hall sensors on our swing arms....
I have asked this question several times before with only vague results.
Our low voltage 5s -6s (<24V ) is not common on those controllers, and the resulting high peak amps ..50 -80+A ... is also beyond their designed range. So there is no "off the shelf" Ebike controller available that would suit, and the only solution currently available is a "custom" heavily modified controller with all the risk that implies.
Hopefully, one of the controllers being developed by board members may provide an alternative for these low voltage "Hall 'd RC" .. drives
This forum owes its existence to Justin of ebikes.ca

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Re: Commuter Booster - <1kg Friction Drive

Post by adrian_sm » Jan 18 2011 5:57pm

Yes it would be a modified controller, but not too majorly I think. If we restrict ourselves to the current capacity of the 4110 fets, then it could still be a robust solution for a low power friction drive set-up. This is particularly relevant if, like kepler, you want a commercial robust & legal product.

- 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
Build #??? ~21kg ~1500w Adrian's Bafang BPM Hardtail MTB Bafang BPM code12, 15s LiPo, ~40kph, ~30kms

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Re: Commuter Booster - <1kg Friction Drive

Post by Hillhater » Jan 18 2011 6:59pm

Lyens 6FET "Mini Monster" is probably the best bet, but that is a 36V (29V LV cut off) design with a 25 A max rating.
Lyen stated that with modification you MAY be able to double the current rating (50A) but even then , modding for <36v is an unknown area. ( and 50A is , i believe, still marginal )
You are ending up with a very experimental controller ! ...and that is without the issues of hall installation in the motors. !
The phrase .." Out of the Frying pan , into the fire" ... comes to mind
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Re: Commuter Booster - <1kg Friction Drive

Post by adrian_sm » Jan 18 2011 7:41pm

Lyen's "Mini Monster" (which I happen to be running on my MTB), is based on a xiechang controller, that has had decent components etc used when building it.

Jeremy is using these on low voltages in his boat, he outlined the mods required here, using IRLB3034 FETs. He managed to get it working for both 12V and 24V, acheiving ~80Amps, or 2kw at 24V.
6 FET Xie-Chang 116 controllers on low voltage

And here is a link to the identified problem of tripping the peak current, and how to fix it.
SOLVED! Infineon Cutting out Question

As for mounting hall sensors, the swing arm seems to be a good base for external mounting. Or go internal if you don't mind cracking it open, enough people are doing it. Or finally we could just go for a sensorless version of the xiechang, but where is the challenge in that :D

None of these sound insurmountable. In fact it looks like all the elements have been done before.

- 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
Build #??? ~21kg ~1500w Adrian's Bafang BPM Hardtail MTB Bafang BPM code12, 15s LiPo, ~40kph, ~30kms

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Re: Commuter Booster - <1kg Friction Drive

Post by Hillhater » Jan 18 2011 8:12pm

Adrian,
i never doubted that it is possible, but you have to admit that is a long way from being a commercial controller !
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Re: Commuter Booster - <1kg Friction Drive

Post by adrian_sm » Jan 18 2011 8:50pm

Hey, so is my Commuter Booster. But if we don't stretch, we won't advance.

And I don't think a modded xiechang is that far behind the other solutions we have on the cards for these friction drives.
Many others have had sync issues with the RC ESCs. Kepler mentions above a few reasons his interface is needed to protect the ESC from our abnormal use. The point is there isn't a perfect off the shelf solution, for this new application.

Of course the modified xiechang would not have the additional FD specific features Kepler's interface will. So it is far from a perfect solution either. I was just pointing out that you could start building these modded xiechangs tomorrow, and have some of the issues ticked off.
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
Build #??? ~21kg ~1500w Adrian's Bafang BPM Hardtail MTB Bafang BPM code12, 15s LiPo, ~40kph, ~30kms

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Re: Commuter Booster - <1kg Friction Drive

Post by Hillhater » Jan 18 2011 10:04pm

Agree that it is an option,..as you will no doubt know from my other posts..i am considering this for myself... but building /assembling a drive package is not easy (as you well know) for even the most determined and experienced, but if we have to get into modifying controllers, or even sourcing custom modded ones.. then even fewer people will be interested. It will be the domain of the exclusive tech-set.
Many of the builds on here..Keplers, Spinners, as well as yours, etc have a commercial potential if not a defined business plan and i am sure they would prefer to be based on proven, readily available commercial components.
I am probably the last person to defend the use of RC ESC's on these drives, but they have been proven to work if correctly matched to the motor, and there is much advantage in knowing that in case of failure, there are multiple sources of spares all around the world, rather than having to source from the one original "custom controller" techspert.

Some time back i enquired to Lyen about this issue, and he actually suggested the best option would be to use the .."12 x 4110 MOSFET Extreme Modder Controller LYEN Edition "... but that takes it up further in size and costs .
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Re: Commuter Booster - <1kg Friction Drive

Post by spinningmagnets » Jan 18 2011 10:42pm

I believe all the pieces are actually on the menu right now, in front of us. If you want a relatively plug-and-play option that is quite small, Matt has proven that the $250 Castle Creations HV-160A is the best.

If you don't mind doing some simple mods to one of Lyens controllers, and adding hall sensors to your RC motor, you can cut that price in half. Not a bad savings for one unit, but if you start getting orders for many of these kits with halls and modded controllers, how much is your time worth?

Few customers want to wait for you to order and then mod up the parts when they've paid ahead of time, so, are you willing to have $125 worth of hardware sitting on your shelf waiting for an order? How much would you have to charge to not only for your time and expertise in doing the modding and making the hall-kits, but also to pay for the occasional warrantee claim?

Just for one kit for myself, The modded Lyens-controller and halls sounds like a fun experiment, but...when the control-system sales price begins approaching $200, its just not worth the customer headaches to save $50 on the price. $100 maybe, but for $50 I'd say to customers to just get the HV-160A...or...mod your own Lyens/halls from info from the threads and pics on ES...

Easy to say "why don't you do that?", but will you do it for me for $160? ($125 for parts, $35 for labor, plus a warrantee)

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Re: Commuter Booster - <1kg Friction Drive

Post by adrian_sm » Jan 18 2011 11:48pm

Yep CC HV-160A would be a reliable choice. Personally I have had no issues with my little Turnigy 85A, and K-Force 100A ESCs. But that could be due to riding style. For the non-ES audience it needs to just work, under all user inputs scenarios. So a few things still need to be sorted out, but Kepler's interface just might do that......
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
Build #??? ~21kg ~1500w Adrian's Bafang BPM Hardtail MTB Bafang BPM code12, 15s LiPo, ~40kph, ~30kms

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Re: Commuter Booster - <1kg Friction Drive

Post by Kepler » Jan 19 2011 12:11am

As good as the Castle Creations 160HV is, $320 is a serious investment (not sure when you get them for $250). Add a $50 Magura, and a modified servo tester and you have a $380 package. Dont think too many FD builders are going to be too interested in that sort of investment.

DIY halls sound like fun but but not sure how many would takle this even offered as some sort of kit. A custom built sensorless 6FET setup for 6S and 50A makes the most sense to me especially considering RPM on a 200kv motor on 6S is around 4800. Most likely source would be from Lyen. Maybe he is already working on it. (I have no idea if he is) But would this guarantee no more sync issues?

Considering the whole point of going down the path of a friction drive is to be small, light weight, and cheap, I dont think we are too far off the mark with what we are doing. :)
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Re: Commuter Booster - <1kg Friction Drive

Post by Kepler » Jan 19 2011 12:24am

adrian_sm wrote:Yep CC HV-160A would be a reliable choice. Personally I have had no issues with my little Turnigy 85A, and K-Force 100A ESCs. But that could be due to riding style. For the non-ES audience it needs to just work, under all user inputs scenarios. So a few things still need to be sorted out, but Kepler's interface just might do that......
100% agree, it just needs to work no matter how you ride it. Not an easy problem to solve and the reason why the interface has taken 6 months to develop. Like to point out over 2000kms have been logged during testing and development. During this time, never had an ESC failure even when pushing them to their thermal cutout point.
Current Rides

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Re: Commuter Booster - <1kg Friction Drive

Post by hillzofvalp » Jan 19 2011 12:46am

I've seen auctions on ebay for CC ICE HV 160s closing at $207USD shipped. FYI.

Can someone quickly clarify what is meant by syncing issues? does the esc shut off as a safety feature as a sort of "locked rotor protection"? Are hall sensors there to prevent "cogging"?

Lastly, what is the story with the C6374 from leader hobby? Does it have skirt bearings? Anyone currently testing it or going to? http://www.leaderhobby.com/product.asp?ID=9394001100037

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Re: Commuter Booster - <1kg Friction Drive

Post by adrian_sm » Jan 19 2011 1:08am

That's the wrong motor, here is the one that Kepler ordered, which hasn't arrived yet I believe.
Which has a skirt bearing, see ...
kepler wrote:This is the motor I ordered. http://www.leaderhobby.com/product.asp?ID=9394001220805
Image
[EDIT] Fixed quote tags.
Last edited by adrian_sm on Jan 19 2011 1:26am, edited 1 time in total.
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
Build #??? ~21kg ~1500w Adrian's Bafang BPM Hardtail MTB Bafang BPM code12, 15s LiPo, ~40kph, ~30kms

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Re: Commuter Booster - <1kg Friction Drive

Post by adrian_sm » Jan 19 2011 1:24am

Update: Dual-personality

I think my drive has a dual personality, which is causing me and others confusion.
It started with personality 1, and is now fighting with personality 2.

Personality 1) The Original DIY
- light weight friction drive <1kg
- good performance >1kw
- cheap parts, see how cheap works
- able to be built with minimal tools, minimal hurdle for people to DIY
- simple
- market, ES type enthusiast

Personality 2) Commercial product
- full friction drive kit
- light weight friction drive, want the bike to still be a bike
- "legal" performance, able to be limited to local legal limits
- competitive total package cost
- initial small batch production to test market
- robust and idiot proof, self protecting
- market, anyone that doesn't think it is cheating

The problem is that these are actually quite different products, and will require different solutions. But I am trying to walk some middle ground ... and obviously failing.

For Personality 1). the mechanicals work, make some yourself and give it a go. But you will need to sort out that electrical stuff for yourself at the moment. There are a few options that should work, not elegant but work, depending on budget vs skill.

For Personality 2)........... well let's just wait and see once I make a few, get more road time, and get some feedback.

Sorry for the confusion people. Just getting ahead of myself.

- 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
Build #??? ~21kg ~1500w Adrian's Bafang BPM Hardtail MTB Bafang BPM code12, 15s LiPo, ~40kph, ~30kms

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Re: Commuter Booster - <1kg Friction Drive

Post by spinningmagnets » Jan 19 2011 2:08am

To be fair, the 160A I mentioned should really only be neccessary for an axle-driven E-bike with an appropriate gear-reduction. There are web-retailers that sell components for noticably less than a seller that must maintain the costs of a physical building. That being said, the "suggested retail" price of the HV-160A is $320 on their home-page, for Motor-shell FDs such as Kep's and Adrians, the HV-120A is $270, and for drives like Todds, Mine, Zibby, and Rearengine (where the roller is only 1-1/4" dia) the HV-80A is $190.

Heres a web-retailer that has over 3000 sales, a 99.8% positive feedback, and regularly sells the HV-160A for around $250.
http://cgi.ebay.com/Castle-Creations-Ph ... 4155aa7c11

The same guy is selling the HV-80A for $130, and the HV-120A for around $210.

If you only need 5S-8S (18V-33V) plus the Castle Creations electronics and chip program for filtering and sensing the back-EMF (perhaps thats the only part of the CC "secret sauce" that we need?),the "non-HV" Phoenix-Ice 100A can be found for around $120. Plus...this model has a built-in BEC, so you dont have to buy a separate UBEC. This is the ESC that Zibby used, and he didn't report any sync issues. http://endless-sphere.com/forums/viewto ... 03#p214997

http://toys.shop.ebay.com/i.html?_nkw=i ... m270.l1313

When the weather clears I will be trying out the $80 Hobbywing ESC I just got. If it doesn't work out, I may get the CC 8S/33V unit next.
Last edited by spinningmagnets on Jan 19 2011 2:58am, edited 1 time in total.

jbond   100 W

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Joined: Oct 02 2010 1:15am

Re: Commuter Booster - <1kg Friction Drive

Post by jbond » Jan 19 2011 2:41am

I wonder how Hidden Power have dealt with the controller issues.

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Kepler   1 GW

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Joined: Nov 08 2009 9:22pm
Location: Eastern suburbs Melbourne Australia

Re: Commuter Booster - <1kg Friction Drive

Post by Kepler » Jan 19 2011 3:04am

Thanks for the heads up on the excellent prices out there. I was under the false impression the CC set the retail price. :)

Spinner, your drive has the advantage of a smaller roller so 8S is certainly a good option. The CC controller will suit this very well.
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gfulton   1 mW

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Re: Commuter Booster - <1kg Friction Drive

Post by gfulton » Jan 19 2011 9:11am

adrian_sm wrote:
Wow. Long time lurker indeed. Glad you dropped by my little thread. :D
Great, thanks. So the startup torque provide enough movement about the povit point to provide initial tire contact. From there the friction would allow the motor to climb until being limited by the deadstop. Sounds perfectly reasonable... as long as I'm understanding this right...
aluminum prototype based on adrian_sm's commuter booster finished and working!
150 kms and counting... ordered 660 Wh of lipos coming soon.
currently have 22.2 volts and 7.5 Ah

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