CroBorg Commuter

[Alan B]

Now back to the Beginning, or how it all started:

Happy Holidays, All.

Let's assume for a moment that Christmas has been good to me and I'm going to get to build a Greyborg Warp with a Cromotor.

http://www.greyb.org

There are many choices to make along this road. Let's visit them and see what folks have to say about these choices. I've read most of what I can find about the 'Borg, but there are many things I have not found on these topics.

Some of my Use Cases:

a) commuting, hilly 13 miles each way, up to 12% gradient, 1200 feet rise one way, 600 feet the other.

b) camping, various terrain from streets to dirt roads and the occasional trail in the desert or Sierra, etc mountains.


I would prefer to keep this a bicycle and avoid having it be too much a motorcycle, insofar as practical. Somewhere between Bicycle and MoPed, perhaps.


Some Choices to make (there will be more later, pick a few to start):

1) motor - Cromotor, other hubmotor, or RC?

2) forks - Standard 'dual disc' offering, or other?

3) crankset - Schlumpf or ?? what gearing??

4) rims and tires - bicycle, moped, or light motorcycle?

Comments, anyone?

Thanks in advance,


Other Greyborg builds and useful links

viewtopic.php?t=25973 RC drive

http://www.carolinarovers.info/index.ph ... Itemid=150 DIY Rivnut Tool

http://www.competitivecyclist.com/revie ... n_779.html stainless chain

http://www.icetoolz.com/icetoolz/news.php?id=9 bike tools

viewtopic.php?f=2&t=31518 current based throttle via CA

[johnrobholmes]

I shall pretend I am building it for myself. I live in a hilly area of Missouri and get horrible efficiency of 40 to 60 w/h per mile cruising 30mph+. A 1kw hour would get me 13miles comfy, I wouldn't want to push it too much further.


Forks- no comment, don't have a good grasp on today's market.

I would set up the bike with DOT lights, in my state it would save me tickets. In your state it may get you tickets since 50cc scoots need a license.

Schlumf drive all the way! Single speed rear. I wouldn't plan to pedal such a bike all the time.

Moped parts are awesome for stout wheels and light weight. 17" rims would give me the most tire choices and a good balance of speed. Puncture resistance is awesome, and DOT ratings ensure a safe ride at speed. They can be used with 13 though 11 ga spokes with great success- and that matches the hub strength that would be used with the forks and frame.


CroMotor would be my choice, if buying a new motor for heavy hills and 40mph top speeds. 9c motors work good, but don't lace up as stout. Puma motors are great too, but the Greborg frame doesn't beg for a light system. It wants moped/ scooter power! Right now a DD motor is the best way to get big power without a frame mounted motor, and that frame is made for a hubbie.



In summary I would lean towards a "moped" style bike that had pedals but was more like a modern 50cc bike in power. It would be heavy, inconvenient to pedal, but awesomely fast for commuting and regular use. It would look like a bike and allow me to go everywhere a bicycle could go, but have a mean streak on the street!

[Alan B]

I like this thinking a lot, John.

I hate flat tires.

Would be nice to have lights that were not really visible when off, that would give options.

With 17" moped rims what does the tire diameter end up being?

[johnrobholmes]

Depends on the tire, but they are pretty consistent between widths.

Measures:

2.25 unknown cheapie slick 22" tall
2.5 Shinko 244 knobbie 22.75" tall
3.0 shinko 244 23.5" tall

I'm pretty sure the knobbies are just a shade taller than a slick would be. 2.5 gazelles are about 22.5" IIRC.



I've been leaning heavy on DOT tires for all my faster builds lately. Bicycle tires work wonderfully, no doubt. I just get a lot more confidence at 40mph on a thicker tire. Now if only we could get radial tires in moped widths!

[Alan B]

I see those tires are DOT rated up to pretty good speeds (like 75 mph).

Would it make sense to use a 2.5" wide rear and a 2.25" front, or make them the same, or does it matter?

So no data on the forks.

Any suggestions for the rear shock?

Brakes. Dual front needs to be hydraulic. Maybe dual Gatorbrakes, or do those have good enough modulation?

[Philistine]

http://www.ebay.com.au/itm/ROCK-SHOX-Bar-1-1-MTB-Mountain-Bike-Air-Rear-Shock-165mm-6-5-x-1-78-/320811759012?pt=Cycling_Parts_Accessories&hash=item4ab1def5a4

I used this rear shock on my greyborg and I have been really happy with it, the air adjustment is good, I know others have used longer shocks, but I find this is plenty of travel, and I think if it was much more it would sit too high.

I think as long as you have 203mm disc brakes on the front, you will be fine with a single disc brake at the front. I got the Rock Shox Boxer forks that Hal/Accountant were selling and they are simply awesome.

EDIT: I should note here, that Hal and Accountant recommend a 175mm minimum shock, with air/spring combo if you are going with the added weight of a hub motor on the rear (or, if, as Aussie Jester puts it, if you have "chunk in your trunk"). I was only noting that I was happy with my choice, but I want to be clear that is not in accordance with the suggested components. Cheers, Phil.

[johnrobholmes]

I personally like 2.5" tires front and back. It rides smooth. 2.25s are good for lighter weight though.

[Alan B]

Great. Thanks.

Today I received tracking info on my borg kit. Arrival estimated middle to end of January.

The adventure begins..

[Alan B]

So what is decided so far:

• Greyborg Frame Kit, with bearings, covers, and steel swing arm
• Cromotor, KV about 9.5
• Schlumpf drive, 1.65x
• Volcano Dual-Disc Forks
• Dual-Disc Hub
• Aluminum Moped Rims, 17"
• Michelin Gazelle Moped Tires, 17x2.5"

italicized items are not yet ordered

Swing Arm Thoughts

The new Aluminum Swingarm looks great, and at first I was thinking it was an upgrade that I wanted. When an opportunity for a steel swingarm surfaced I was at first planning to wait. Then I realized that the steel swingarm looks more "bicycle like" whereas the aluminum unit looks more "motorcycle like". So I decided to go for the steel one in keeping with trying to keep this thing close to a bicycle.

Rim and Tire Thoughts

So then why consider a moped rim and tire? Flats are a real problem on an e-bike, especially on a hubmotor. Also at higher levels of performance the bicycle tires become unsafe. The moped tires are DOT rated, some for 75 miles per hour, and are tougher than bicycle tires. They still appear bicycle like, so hopefully this will make a reliable and safe upgrade for this project.

Schlumpf Drive

There is not much room with the wide Cromotor for a derailleur. There is not much room for a large front chainring due to the battery covers. The Schlumpf helps this out by providing a two speed crank with planetary gear speed up (1:1.65) when in high gear, and 1:1 when in low gear. So if a 34 tooth chainring is employed on the crank, it will give an effective 56 tooth chainring in high gear.

[Alan B]

Battery Selection

I'm not looking to break any land speed records, so the motor's KV of about 9.5 should be fine for me. With 18S Lipo this would put top speed about 37 mph with a 24" diameter wheel. I use 18S on my other ebike so this would be a good selection for charger sharing. Choosing 18S for now.

Controller Selection

Lyen lives not far from me and has a good selection of controllers and good service, so I was reviewing those. There are a couple of choices that fit well for this setup. The 18 FET 4110 model and the 24 FET 4110 model. They are both rated up to 100 volts (18S is 75 volts hot off the charger). The 18 FET model is rated at 65 amps and the 24 FET model is rated at 100 amps. This would be about 5KW versus 8KW. For comparison my 9C motor runs about 3KW on a 12 FET controller at 40 amps.

Motor Saturation

The question is - at what current does the motor begin to saturate? I generally want to operate up to the first knee where the torque increase per amp changes to a smaller value, this is the best efficiency range. For the 9C this occurred at about 450 amp-turns. But I'm not sure we have this data yet for the Cromotor. I'm not sure yet but the Cromotor may be 4 turns. Since the Cromotor is sort of a double 9C this might make it similar to a 9C 8 turn wind with a 55 amp first saturation point, so that would make it about 110 amps with half the turns. There are so many differences between the 9C and the Cromotor that we cannot assume too much from the similarity though. The Cromotor probably uses better lamination steel than the 9C and this could further raise this current level. Also if the Cromotor is not 4 turns that changes the result significantly as well.

Details

The 24 FET controller is larger, heavier and more expensive. But it has more capacity without "hacking" it. I see folks using both types.

So is there a consensus on this?

[BlackArrow]

Hi Guys,

Wow it will be a nice project and it's already have allot of good informations and i will use it for my new project. Alan a 18 mosfets if you beafier the trace a little is much more capable than "only" 65 Amps, Lyen can help you on that one for sure.

Good day!
Black Arrow

[mabman]

As a long time user of Schlumpf drives and having owned all three models I would recommend the high speed drive instead of the speed drive for your build. You still get the 1:1 but the 2.25:1 yields an even higher gear which suits motor assist better if you at all like to pedal at speed?

For example I use my Townie with 28" wheels with a speed drive with my 1000w 48v pusher and with a 37/12 (6 spd freewheel) I can stay on top of the motor ok up to where it cuts out at 20 mph. Without the trailer it spins out at about 24 mph. So especially if you use smaller diameter wheels it can be a factor.

0306001816a.jpg (63.25 KiB) Viewed 6857 times

The Schlumpf on that bike is over 10 years old btw and still going strong.

[Alan B]

Thanks for your comments mabman. Glad to hear they hold up. You have been on the board here a long time.

You are probably right about the high speed drive being a better choice. It has something like 2.5x ratio.

Edit - Note the 37 tooth chainring was wrong, correcting to 27 or 34 for the two sizes available for the speed drive.

I am curious, though. With a 27/12 the 1.65x of the speed drive should give you 44.6/12. Presently I have 48/14 and I can pedal almost to 25, and my cadence is not really fast, I think. That's with 26" wheels.

Lets see what I've got:
25 mph is 2200 feet per minute
26" wheels have 6.81 feet circumference
so wheel rotation is 2200/6.81 = 323 rpm
48/14 gear ratio is 3.43x
so crank rotation is 323/3.43 = 94 rpm which is high for me, not doing much at that rate.

Now let's see what happens with your setup:
24 mph is 2112 feet per minute
28" wheels have 7.33 feet circumference
so wheel rotation is 2112/7.33 = 288 rpm
27/12 times 1.65 speed drive is 44.6/12 = 3.7125x
so crank rotation is 288/3.7125 = 78 rpm which is not terribly fast, but a good cadence.

Now lets look at this borg setup I'm planning:
30 mph is 2640 feet per minute (arbitrary speed selection)
so wheel rotation is 2640/6.81 = 388 rpm
with 34/14 and 1.65x Schlumpf effective 56/14 and ratio is 4.00
so cadence is 388/4.00 = 97 rpm which is high for me but this is 30 mph! (and that's where I am now at 25 mph).

So I probably do NOT want the 27 tooth chainring!

I don't generally compute cadence, I think mine is 60-80 generally. 100 is probably too high, but I am improving there since with the electric drive I can spin with light loading work up. One problem is I don't want to clip in. But perhaps good pedals would make a difference, I've never had anything very good I suspect. Pedal suggestions?

I do agree that the high speed Schlumpf would be great on this bike. That would allow the low range to be lower and the high range to be a bit higher. There was a major step in price for that model so I didn't go for it.

[Alan B]

Looks like I have the wrong chainring on the Schlumpf. It comes with a 27 or a 34 tooth. Not 37. Don't know where I got that number, but that explains the difference. I'll have to redo the calculations above later. Done.

[mabman]

Yeah, my bad typo wise. Both my speed and high speed drive have 27t chainrings. My mtn. drive has a 40t. I used it on a FS 29"er I had a number of years ago.

BTW I have the chamfering tool also but it is on loan right now with a friend in MI. If you need it I can pry it out of there as he is done with it.

[Alan B]

Yeah, my bad typo wise. Both my speed and high speed drive have 27t chainrings. My mtn. drive has a 40t. I used it on a FS 29"er I had a number of years ago.

BTW I have the chamfering tool also but it is on loan right now with a friend in MI. If you need it I can pry it out of there as he is done with it.

I may need a chamfering tool. I know of a shop that probably has one so I may have them do it, but I will keep that in mind if that doesn't work out.

Thanks!

Are the chainrings and cranks standard? What fits it??

[Alan B]

Greyborg side cover designed for 34 tooth chainring but could take a 36, according to Hal's posting at the bottom of this page:

viewtopic.php?f=6&t=25459&start=30

Edit - email from Accountant indicates that 38mm may fit.

[Alan B]

Common single speed freewheels available down to 16T. Getting below that is difficult.

So let's assume we get the 34T front chainring, and the 16T freewheel.
Lets also assume the Gazelle 2.5 tires are 22.5" OD.

spinning pretty fast at 90 rpm:

90 * 34/16 * 1.65 * pi*22.5/12 / 5280 * 60 = 21 miles per hour in high gear

90 * 34/16 * 1.0 * pi*22.5/12 / 5280 * 60 = 12 miles per hour in low gear

at a more comfortable 60 rpm:

60 * 34/16 * 1.65 * pi*22.5/12 / 5280 * 60 = 14 miles per hour in high gear

60 * 34/16 * 1.0 * pi*22.5/12 / 5280 * 60 = 8.5 miles per hour in low gear

[Alan B]

Battery Musing

There are two battery compartments in the frame: 300x150x105mm

6S 30C 5AH Turnigy packs are: 145x50x50

so if we rearrange the battery dimensions to match the 'borg dimensions: 50x145x50

And then divide to see how many will fit: 6x1x2 = 12 in each area, 24 total

24 x 6 x 3.7 x 5 = 2.7 kilowatt hours

But is there room for the wiring?

Can this ACTUALLY fit?

[Philistine]

I fit 8 x 5S 5ah turnigy bricks in the top box and the bottom box (to give a total of 20S 20ah). Keeping in mind that I had built aluminium boxes (out of angle and sheet) to fit into each space, to protect the lipo. But in those boxes it was a tight fit but that is because I had not done a good enough job of minimising my wiring harness, there was heaps of excess wiring to fit in. I will be interested to see how you go, because when these packs retire in a year or two, I would like to move to 24S, but I was concerned that it might be a bit tight width wise, as in my boxes there was only a few mm spare with the 5S packs side by side. I also wondered about how 8ah packs might go, but I haven't go around to using one of my 8ah packs to look how it would fit, I will do that the next time I have the covers off.

Good luck with it.

[Alan B]

The boxes take space and prevent the wiring from using the free space in the frame, so I'm thinking of less protection. Would be great to get 18S8P or 24S6P in there, but I suspect it will be too tight and it would be pretty heavy. Just have to wait for the frame to look at that. Ideally half the pack could be easily removed so the weight could be adjusted when the range wasn't needed.

Wonder how much Pike's Peak would require..

[mabman]

Are the chainrings and cranks standard? What fits it??

The chainrings are not standard.

The left crank is a standard one but the right (drive) crank is not. It has no spider for holding a chainring and looks like a non drive side crank but it needs to have the same threading for the pedal spindle as a drive side crank normally would or else your pedal will come off. I just use Florians cranks, 170mm btw. They are not the most beautiful ones out there or lightest made out of the swankest carpet fiber but they work just fine for their intended purpose.

[Alan B]

Did some research on freewheels tonite.

Smallest with the standard ISO thread that hubmotors have is usually 16 teeth.

AC Racing had a 15T model that fits but the reliability was poor.

White Industries is highly rated, about $80.

Anyone have comments on stainless steel chain?

[Alan B]

Zippy Lipo

The 6S 8AH variety is appealing due to the fewer interconnects required. The size is:

165x69x52

Unfortunately this just doesn't fit the available space well at all, neither the 300 or the 150 mm dimensions.

[Alan B]

Chain Issues

I would like to keep the hubmotor wheel fully forward in the dropouts for torque reasons. This leads to a chain tensioner. I really like the look of the Surly tensioner. It mounts on a derailleur hanger, which I think the 'borg has.

Of course it is one more thing to hang out and get broken in a fall.

Thoughts?