I have been getting a few questions on my Borg project, so I thought a recap might be in order.
I started this thread on Christmas Day about four months ago. My hardtail mountain bike was coming along nicely, but I wanted more. Better suspension. Better tires. More torque. The HT3525 I had just purchased was still in the box and I was already realizing it wasn't enough. On the Marin group trip I came very close to smoking my 9C 2810. It was really hot for hours, and didn't really have the torque even at 72V to make the climb well. On the work commute the rough roads and gravel were a bit more exciting and distracting than I like. It works, but I wanted more.
So I started looking at full suspension bikes. Downhill bikes are really nice, and expensive, and not suited for batteries, and not really the right suspension for street riding, or carrying loads. I'd like to have one for dirt, but that is a big project for another day.
I wanted a comfortable ebike with plenty of power for hills, plenty of capacity for longer rides, and lots of rubber to soak up the gravel, pavement, and thorns without excitement.
The Cromotor looked like the deal, and there was one available. I checked with Accountant to see when Greyborg frames would be available, and they had one left.
I ordered them. I knew they were arranging a US dealer which would be a better way to go, but would not be ready for awhile. I also knew this was a significant project, and I have many other projects, so this was going to take a while. I have the other ebike so that's okay.
Pretty much every turn in this project has been delayed. I didn't expect anything else, so all is fine. The shipment took awhile. Some parts were missing (probably removed during shipment), so another shipment (great service from Accountant!). There was some shipping damage, so add some repairs. There are a lot of components on a bike, and the Greyborg I'm building is not using the most available stuff. Dual front discs are hard to come by. Stevil found some for me, THANKS! Four pot Gatorbrakes for Tadpole Trikes. Chainrings and crank arms for the ATS Schlumpf two speed crankset. Thanks to Accountant for the crank arms and Ebay for the 34T 110 BCD Chainring.
I wasn't looking for a racing machine, though Stevil has shown that it can be one, and Zombiess has shown that the Cromotor is racing capable as well. I'm really looking for what Hal was building - a really competent commuter. This Greyborg Warp can be both, apparently.
When I ordered the 'Borg I'm not sure I had a fully developed wheel plan, but the 17" Moped wheels appealed to me. I had a Motobecane Mobylette moped and put thousands of commute miles on it going to college. In years of use it had maybe one or two flats. I don't think I ever replaced a tire. It was a killer to pedal if you ran out of gas, and it was a dog going up the hill at work at 9 mph and pissing all the cars off. The brakes were almost good enough to stop me going back down that hill. But you had to anticipate the light or you might have to dig in your heels to get stopped.
The suspension was better than nothing. The Greyborg Warp with Cromotor will so outperform the Moped in every way except range and recharge time.
So 17" Moped wheels with 2.5" tires are about 23.5" OD so comparable to 24" bike tires, pretty much. But instead of a few ounces of rubber you have over 4 pounds of 70 MPH DOT rated rubber. Serious stuff. I was going to use 2.5" Gazelles on both ends as recommended by JRH, but I liked the 3" that Stevil had on his rear tire which fits fine in the Borg frame, so I'm going to try that (2.5 front, 3.0 rear). More rubber! Depending on the battery complement this bike will be nearly 100 pounds, much like the Motobecane Mobylette moped was for weight.
Lacing the Cromotor into a rim is a challenge because it has about 3.8mm holes which is a bit large for 12 gauge spokes. 11 gauge might fit but those won't fit the moped rims. I suppose they are sized for motorcycle rims. So you can drill new spoke holes, or use washers. We'll try washers first.
On the front hub you have the opposite problem. This hub is made for dual discs but probably 13 gauge spokes. So it will have to be drilled out slightly to fit the 12 gauge spokes that the rim wants.
I was looking at Kiwi's beautiful Borg torque plate, but I was concerned that it might be a bit thin for this double-torque motor. Then I find out that the Cromotor has 16mm axles flatted to 10mm so they won't fit the Kiwi plate, and the axles are not really long enough to fit thick torque plates, and that no torque plates are needed if the Cromotor is seated fully forward in the horizontal Cromoly Steel Borg swingarm dropouts. So I bought half-link chain and plan to seat it fully forward. Stevil used a floating chainring (like Luke does) to provide the fine adjustment so the motor can be fully forward, so I can do that too if needed.
I was going to have Magudaman (who is also local here) make some custom torque plates, but there isn't room for them. I was also going to use the new alloy rims that JRH is having made, but they are way late and Stevil made me an offer I could not refuse.
He's just over an hour from me so that avoids shipping.
The rear brake mount that Accountant supplies has a 12mm hole to go on the axle, so I'm not sure what to do there. Drilling it out to 16mm won't leave much material. I may need to have something fabricated. Perhaps Accountant has something for it now that the Cromotors are going to all have the 16mm axles? Didn't Luke say the rear brake was optional? Sheldon Brown doesn't seem to think they are needed much (see his encyclopedic bike website in the braking section). I will do a rear brake, though, and Regen. Soon.
Philistine had the Lyen 24 FET controller in his Borg, and I decided to follow that track. The 18 FET is undoubtedly adequate, but for solid reliability I wanted to go with the 24. I had Lyen build me one. Mine seems just a little to be too long to fit in my frame, but I'm going to review that again before I cut it shorter. Either way we'll get that in. But if you want an easier project choose a smaller controller.
I want to be able to pedal, both to get some exercise, and to be able to go on bike paths. Derailleurs are a problem, and the Borg isn't really set up for them, so I chose the ATS Schlumpf two speed planetary drive crankset (with excellent pricing from Accountant). With the 34 tooth chainring and the 16 tooth single speed freewheel I will get about 12mph in low gear, and about 20mph in high. A larger chainring could be used by leaving the plastic off the chainring side, perhaps fabricate a flat panel to go there.
For forks I have the Volcano set up for dual discs from Accountant. Nice pricing and should be adequate for commuting. Don't need too much travel, this isn't a downhill machine and I don't plan to jump it.
Stevil is helping me out with FSA Pig DH Pro headset and Ritchie adjustable stem. (Thanks!)
I took Oatnet's suggestion of a Cloud9 seat, and he also suggested adjustable stems. I have a seatpost but need to do some sanding to get it to fit in the tight seat tube.
I decided to go with the White Industries freewheel but find that it doesn't fit on the long motor threads as far down as it should (someone warned me about that), but I learned that it is machinable stainless so I can fix that. But I ordered a Dicta (which has threads all the way through) to start with, then I'll decide later to fit the White or not.
In the midst of my Borg build I was reading about the Mega Enduro ride that Lyen has chronicled, and its requirement for less than 20 watt hours per mile. That, and the long time in the saddle convinced me that I needed to try a recumbent for the occasional longer touring ride. I dialed up Craig's list and there was a bikeE just a few miles away, inexpensive, in good condition and barely used. I ignored it for nearly a week and then zoomed over there before someone else scooped it up. I put a BMC on it from Ilia at ebikessf. It is amazing but in no way replaces the Borg. It is light and efficient and wonderfully comfortable (aside from potholes), but for daily driving on rough and steep roads and competing with cars the Borg is preferred. I'll have them both.
So when is the Borg going to be on the road? Soon I'll have wheels, headset, stem, and some assembly to do. Still need to get the ATS Schlumpf installed, sort out axle spacers and chainline, figure out the rear brake (or temporarily skip it), mount some cover panels, and do the wiring.
AND the batteries. Stevil has a system for making up packs on the fly using the hardcase Turnigy bricks, he makes up a pack for what he needs and straps it in the Borg. Very clever and lightweight. I like the modularity.
I tend to think more in terms of a mounted pack and onboard charger that is more than adequate for the daily commute, and then a longrange secondary pack that is added when needed. Methods HVCLVC boards. The Cycle Analyst V3beta is in hand. But the battery pack is still theory. I'll probably start with 15S 8AH Zippy that I have sitting around, and then get some Turnigy 6S bricks and start aggregating a full set.
I have been looking at the ebikes.ca simulator. Thanks to Justin and zombiess for putting the Cromotor's measured data in there (NoName5004). It may not be perfectly accurate, but it is really useful to get some idea of how things are going to work.
I have the 2810 on 18S lipo at LVC of 3.6V on a 26" mountain bike (like my setup) to compare with the "CroBorg" (coined a new term there?). (this is done by selecting a 2807 and scaling the values since the 2810 is not there). This compared to the NoName5004 (which is model data based on some measured values from a Cromotor).
So I'm looking at 12/24S or 18S. Being an engineer I don't want to run my 100V 4110 FETs at 24S all the time. There's just not enough margin. So I thought about using a 12S/24S switching setup, then it would spend little time at 24S. But do I need 50 mph? That's just going to be trouble in so many ways. Sorry Luke.
So back to 18S. My original plan. How does that look? 2KW into the 9C, 4KW into the NoName5004, so very conservative. At Low Voltage Cutoff (3.6V) ( so it will be better than this ) the mountain bike with 9C 2810 gets 25 mph. That's about right, I see about 28-30 hot off the charger. What about the NoName5004 in 24" tires? Well it matches the 9C at 65% throttle. The efficiency of the NoName5004 is just slightly better than the 9C. Using better materials does make a difference. It rocks
So what about the rest of the throttle? The NoName5004 at 18S in 24" wheeled mountain bike makes 37 mph at LVC. Hot off the charger will break 40, especially in a tuck. On a recumbent with a 26" wheel, wow, look out 50. But I'm not going there now.
Thrust off the line is exactly double at 72.5 vs 145 pounds. The torque of the NoName5004 is just less than double the 9C at these power levels, but the smaller moped wheel makes the difference.
You can push both the 9C and the Cromotor a lot harder than this. These are efficient, conservative commuter power levels. I'm quite happy with 2KW in my 9C for most things, and doubling that should be really, really excellent.
So I'm looking for a good 170mm rear shock for the Borg, let me know if you have any leads!
Thanks to ES, Fetchter, Justin, Luke, Stevil, JRH, Oatnet, dogman, zombiess, methods, green machine, HAL, Accountant, icecube57, Philistine, amberwolf, Ilia, Lyen, grindz145, Kingfish, gcindc, markobetti (an incomplete list in no particular order) and all the other folks who have helped to make this happen!