A DB mountainbike, my 2nd build in progress, "The Rolling Firehazard"

[Papa]

Quality control on those things isn't very good it seems...

Could be, but interestingly enough, there appears to be counterfeit G62's (no surprise, eh?). I have a sizeable stash of G62 images, and there's a number of major differences between Grin's sample and others I've found. Beyond the bearings (just one, and I'm probably nit-picking about it), I'm not displeased with QC.

 

[The Toecutter]

I've been riding this around and when using the throttle, it developed a refusal to move when stopped. I have to get the bike moving to about 1.5 mph before the throttle will allow the motor to turn. Otherwise, the motor simply stalls out. This is the case even after removing the rear brake rotor.

Regen also refuses to work unless I use the throttle + brake lever. I don't know what CA setting might be causing this, but I'd prefer for regen to activate just pulling the brake lever by itself.

Trying to get all issues sorted and have this thing reliable before I start taking apart the Milan and giving it its much deserved upgrade. The Milan going to be down for at least 2 days, so this mountain bike needs to be there as backup.

 

[The Toecutter]

I have this thing reliable enough to use now, at least with the throttle. A better-built storage rack was installed and my battery moved onto it, and no problems with about 300 miles of use so far.

With a 750W limit, full throttle, and hard full-effort pedaling, it does 37 mph. Throttle-only, 30 mph.

The Wh/mile consumption for this bike is about 3-4x that of my coroshelled trike at 30 mph. Its range is absolute crap as a result. I can get 25 miles at 30 mph on a good day. This is using just one of the two Greenway 46.8V 15.6AH packs in my possession. Two Greenway 46.8V/15.6AH packs in parallel was enough for 150-200 miles range in the trike at the same speed. This bike's efficiency is absolutely abysmal. At a steady 30 mph on flat ground, this 70 lb mountain bike with its fancy PMDC hub motor is half as thirsty as my 1,850 lb electric Triumph GT6 conversion that uses a 1970s-era series-wound DC forklift motor mated to a manual transmission.

More proof that aerodynamics is everything when it comes to efficiency at anything over jogging speeds.

I fixed the regen issue by disabling proportional regen. Now the motor stops th bike when I use the brake levers, as it should.

I'm also having torque sensor woes with the Sempu. The CA3 shows the P section toggling rapidly up and down, easily 10+ times per pedal rotation, and D side doesn't toggle at all unless I take my feet off the pedals. I don't get an RPM reading, but I do get a torque reading and corresponding appropriate voltage reading. I ordered a new/different torque sensor from Grin that is supposed to work out of the box to replace it, because I hate using throttle only and like the exercise.

Once I get the torque sensor sorted out, I will then spotweld up a pack of Panasonic NCR18650GA to fit into the triangle of the frame. After that, I can start working on a faring.

I also might upgrade the front brake to one of these from the cable-pull Avid BB7 I'm currently using:

The JFC Hydraulic Disc Brake for Pedicabs - Unbroken Components

It will be necessary if I go to a 72V system that can hit 45 mph. I also think dual motors/AWD will be in this bike's future. That would be handy to have in the snow.

 

[nicobie]

Any pics yet? I'm curious.

 

[The Toecutter]

Any pics yet? I'm curious.

Took some just now. This build was much easier and nowhere near as impressive as my first one, but it will get me around if the other two are being worked on.

Note the bald-ass Schwalbe Marathon Plus Tour in the rear. Before upgrading the trike to a 20" 3T wind Leafbike, I was doing a LOT of burnouts at 2,500W on that motor/wheel/tire combo. With 10kW, a Molicel P42A pack, 3T Leafbike motor in a 20" wheel, and a BAC4000, the trike became just plain retarded! The trike is in a bunch of pieces now and being upgraded to AWD and 20+ kW, and I've been using the unmotorized Milan as my primary transportation, so I needed the mountainbike ready to daily before I can convert the Milan. This mountainbike is going to get a new set of tires, probably Schwalbe Marathon Plus Tour 26x2". Eventually, I don't see myself going beyond 2 kW or so with a single motor on this mountainbike because that is all that I will be able to make with an NCR18650GA pack that will fit in the frame triangle. If I upgrade to dual motors, I might eventually do 5 kW or even 10 kW, but that will also require another battery upgrade, and the bike is too short in wheelbase to sustain more than about 35-40 mph comfortably, and I'd want at least a hydraulic brake up front for that.

The rear rack will eventually become storage space, and I have a similar front rack that I can put on the fork that's laying on the floor uninstalled for more storage space. The current fork won't fit that front rack because of the curves it has present in the mounting area, and that rack cost me $100.

I also plan to put a faring like this on the front of the handlebar area:

Amazon.com

www.amazon.com

...and then use foam to build farings for the sides as well, covering up the battery/controller/wiring, and possibly making for a more comfortable motorcycle-style seat than that post-type seat.

Also going to order Mooneyes for the rear wheel to further help with the aero. It really needs it.

I may be able to cut the drag by as much as half, and thereby almost double the range on a given battery pack size.

 

[Papa]

..... the bike is too short in wheelbase to sustain more than about 35-40 mph comfortably, ....

 

[gromike]

Yeah, I am of the opinion that if you want a motorcycle, get a motorcycle.
This is spoken from one who has a couple of gassers, though I will have a battery motorcycle in the not too distant future.
If you have come off a bike at 20+ mph then you will know that you want the best thing that you can get between your legs. If you're doing 40+ on a bicycle all I can say is vaya con dios.

 

[The Toecutter]

Yeah, I am of the opinion that if you want a motorcycle, get a motorcycle.

I'm looking for an ultralight vehicle that is somewhere between a bicycle and a motorcycle. It needs to be light enough to pedal with a disabled battery/motor/controller, but with durable enough components and of sufficient operating dynamics not to get the rider killed when operating at motorcycle speeds.

The components to make such a vehicle possible are generally non-existent. Motorcycle parts are 10x too heavy and at least as much overbuilt for the application and a bike using them will be for the most part unpedalable due to mass. Motorcycle parts, including some of those used in mopeds capable of only 30 mph, are made to allow a 500+ lb motorcycle to travel at and brake from 100+ mph. But bicycle parts are much too fragile, short-lived, intolerant to abuse, and unreliable, because they're made to allow a 30 lb bicycle to travel at and stop from 25 mph. I don't want either extreme. I want a vehicle that maybe weighs 100-150 lbs and only needs to travel at 60-70 mph. No one makes parts for that or a vehicle optimized for that use case. If you want to buy a car capable of sustaining 70 mph, the cheapest options are able to sustain 100+ mph. Vehicles capable of those speeds are ALWAYS overbuilt with greatly more capability than what is actually necessary or safe to use, using heavier parts requiring more materials all so that the manufacturer can charge more and nickel and dime the operator every step of the way. Which is diametrically opposed to cost-saving inherent in micromobility solutions such as ebikes.

20-25 lbs added mass on the various components of such a vehicle in terms of brakes/wheels/tires/frame over what would have been bicycle parts should be sufficient, while motorcycle parts will instead add 200+ lbs.

That is the issue. The parts needed for such a vehicle aren't readily available. Hardly anyone designs or makes them, and fast ebike makers just buy unoptimized parts off the shelf, almost exclusively toward the fragile/less-reliable bicycle end of what is available between bicycles and motorcycles.

I'm surprised Sur-ron never designed their own braking system and wheels in-house and offer the parts for sale to ebike builders in order to address this. The brakes and wheels on that Sur-ron are woefully inadequate given its acceleration and top speed performance capabilities. Which is a shame, because it is otherwise a very capable beast with a well designed frame and suspension, but a beast rendered needlessly dangerous to use to its full capabilities due to lack of many other parts designed adequately for the application. And carefully riding a Sur-ron at 30-35 mph because that's what its brakes/wheels/axles/hubs can safely handle, really is a bummer, when the damned thing is capable of 0-60 mph acceleration in 7 seconds. 10 lbs of added mass in the right areas all over the whole of the bike would make it safe to cruise at 70 mph, but the parts needed do not exist on the mass market.

It took a lot of research to find some of the "middle ground" components for my electric velomobile build, and many components(such as spindles) I'm going to have to design myself from scratch because what I was able to obtain is not adequate for the speeds I'd prefer to operate it at(doing 50 mph down Lindbergh Blvd with the car traffic, for example). Car parts are much too heavy, and bicycle parts mostly inadequate. The Avid BB7s I used to use, one of which is now on this mountain bike, have given me plenty of scares. In the velomobile, a panic stop from 45+ mph in the left lane to stop for a newly-red traffic light and subsequent 50 mph cross traffic while bombing down a hill once had the rotors glowing red and almost pulled me into a wall in the median or a minivan in the right lane! And it didn't even have a motor at the time...

 

[Papa]

I'm looking for an ultralight vehicle that is somewhere between a bicycle and a motorcycle. It needs to be light enough to pedal with a disabled battery/motor/controller, but with durable enough components and of sufficient operating dynamics not to get the rider killed when operating at motorcycle speeds.

At, say, 50mph, you're gonna be equally, physically vulnerable saddling a 900 pound Milwaukee Vibrator, as saddling a 100 pound two-wheeler. One must ways keep in mind,... that your exposed body parts are traveling at the same 50mph speed as the vehicle you're riding... irregardless of the vehicle's 'durability'. However, minimizing gross vehicle mass does have the collision avoidance advantage of quicker, more responsive evasive maneuvers.

The parts needed for such a vehicle aren't readily available.

Then improvise, fabricate, ... the hallmarks of DIY.

 

[The Toecutter]

At, say, 50mph, you're gonna be equally, physically vulnerable saddling a 900 pound Milwaukee Vibrator, as saddling a 100 pound two-wheeler.

Yes, but the 100 lb two-wheelers available are almost always built inadequately for the task from the standpoint of mechanical robustness. The brakes are generally inadequate to stop the thing reliably without eventual failure, as are the wheels, axles, front forks, ect. inadequate to avoid random failure if you regularly push the bike to its limits.

I'd be inclined to trust the Milwaukee Vibrator to take regular abuse and not to have a mechanical failure that results in me unintentionally dismounting the bike at speed, vs the 100 lb two-wheeler. Staying on the bike, keeping control of the bike, and being able to stop the bike are all of significant importance from a safety perspective, especially when surrounded by multi-ton vehicles operated by Boobus Americanus(and in my neighborhood, subspecies Boobus Americanus Ghettopotamus) paying more attention to their ironically-named smart devices than what is on the road.

 

[2old]

It seems (to me) that the hydraulic 4-piston brakes used by downhill racers and thicker discs would help.

 

[The Toecutter]

It seems (to me) that the hydraulic 4-piston brakes used by downhill racers and thicker discs would help.

The size of the fluid reservoir, the type of hydraulic fluid used, and the selection of brake rotor must be carefully considered in the context of the bike's capabilities. Such systems that I've seen used on high-end 70+ mph ebikes are inadequate.

 

[The Toecutter]

The new bottom bracket torque sensor arrived from Grin. I installed it and it works wonderfully, right out the box. The Sempu never did work correctly, but it worked enough for my use case in the trike.

This bike is a lot more fun and useful with this feature. I also upgraded from a thumb throttle to a twist throttle.

This coming weekend, I'm going to try to spot weld together a new pack to fit into the triangle of the frame. Should this work to my liking, I can increase the power to 2 kW. The Greenway packs are going to go into the Milan SL, which is also being converted.

 

[Zambam]

I'm not confident this thing could handle 40 mph on bad roads. I have a cheap Suntour Sr. fork up front and a coil shock for the rear. On known roads that don't have bad potholes I think it could do it, but I have mechanical disc brakes and probably wouldn't want to on a regular basis.

Maximum planned cruising speed will be 25-30 mph. A properly designed set of fairings could increase range 30% or more at speed.

The frame mine has is the stronger replacement version without the defect. It IS aluminum though. I tried to find a used steel dual-suspension bike in my local area to no avail. Everything is either aluminum or carbon fiber now... including and especially so the high-end stuff. What sold me on this one was that it still used 7-speed components, which are nearly ubiquitous in the ebike world and which I had parts for.

What do you think of this damaged fairing, how much range increase will it add (after some fiberglass work)? I picked it up in an evening walk around the track @ a Laconia Classic AAMRR race in Loudon NH late 80's (I was a spectator). Somebody (#37) crashed/ abandoned it. I think it's from a Yamaha YZR 500 two stroke. The clear shield I must have bought because there's not a scratch on it but it does not seem to fit the fairing. Both dug out from the garage today, where it's been all these years.

 

[Chalo]

Tail fairing works better, if you can only have one or the other.

 

[Papa]

But bicycle parts are much too fragile, short-lived, intolerant to abuse, and unreliable, because they're made to allow a 30 lb bicycle to travel at and stop from 25 mph.

Pro DH'ers would probably disagree.

Vital RAW - DH Bike Abuse from Mont Sainte Anne World Cup

It must be noted that plenty of bikes were abused during the making of this Vital RAW. Mont Sainte Anne is ruthless.

www.vitalmtb.com

I would also add.... a decent quality 'bicycle' dual rotor front hub w/precision ceramic bearings and an chromoly axle, will more than survive 60-70 mph punishment.

It is NOT the component choice that'll get'cha killed at 60mph on a bicycle... it's the overall geometry, wheelbase and poor CoM location that'll do it. And yes.... 2 ton road idiots also.

 

[Zambam]

Tail fairing works better, if you can only have one or the other.

Wouldn't that look weird? Can you show some examples photos?

 

[Chalo]

Wouldn't that look weird? Can you show some examples photos?

Here's one from 1913. Most modern examples are on recumbents, because things that make bikes awkward and difficult to use come naturally to recumbent enthusiasts.

To be fair, I don't have any firm data to show that the potential drag reduction of a tail fairing is greater than a front fairing. But I have heard it from aerodynamicists who know more than I do about this stuff. What I do know is that not all front fairing make a bike or motorcycle less draggy, and some increase drag versus no fairing.

I also know that if people have been messing with bike fairings for way over a hundred years and haven't yet come up with something good enough to have become common, that suggests they really aren't worth it. Even motorcycles mostly use fairings for rider comfort and protection only, and address performance issues by throwing more power at the problem.

The biggest part of the aerodynamic picture for a bicycle is the rider, not the bike. So downhill speed record cyclists fair their bodies rather than only their bikes, and the focus there is on trailing edges even more than leading edges.

 

[The Toecutter]

What do you think of this damaged fairing, how much range increase will it add (after some fiberglass work)?

You will have to try it and see. I'll make an educated guess and say that a 10-20% reduction in energy consumption is possible with only a front faring, properly placed. You'll lose out on cooling of the rider in hot weather.

Tail fairing works better, if you can only have one or the other.

You can have both, but there are always tradeoffs...

This Aerodynamic Electric Motorcycle Should Exceed 250 MPH | Carscoops

Cd of 0.12 for an upright motorcycle is damned impressive. To make the above work for a bicycle, it would take some very creative frame geometry with a unique bottom bracket placement, and wouldn't be very ergonomic or comfortable for the rider.

For a more practical and bicycle-friendly approach, that isn't nearly as dramatic in its appearance or results, see the following:

The Rare Bicycle with a Fairing

Hutch BMX Superbike at an antique Bicycle auction! - BMXmuseum.com Forums

My plan is to build a custom side faring that doubles as a seat and battery/controller housing, and add a front faring, as mentioned in the first post. I do not plan to fully fare my front wheel as that induces side-wind instability, but back wheel is getting a 26" Mooneye. It might end up look somewhat like the Hutch bike linked above, except with a motorcycle style seat, where I sit more rearward, and bent over more to still reach the handlebars while getting my head lower to improve the effectiveness of the faring, while still having enough length for my legs to make a full pedal stroke. I plan to do my own art on it and make it have a bit of cyberpunk/post-apocalyptic aesthetic to it, to look as if it was cobbled together from junkyard parts.

I'm not expecting the massive results on drag reduction that I got with my trike, but every bit helps. If I can get 30 mph energy consumption using throttle-only down to 20 Wh/mile, that would be quite something for a mountainbike conversion. Right now, it's about 30 Wh/mile to hold 30 mph using throttle-only. I set my power limit to 750W, but for whatever reason, the CA3 is letting it draw slightly above that, around 900W(probably from battery current settings not being low enough to truly limit draw to 750W). With hard pedaling, for short durations, my legs can add another 750W or so and the motor is clearly not at its usable power limit based on voltage because the speed can still climb to 35+ mph with me pedaling my ass off and I can feel the motor still giving assist. A 20-30% drag reduction will have a positive impact on top speed and range for sure.

I'm thinking of using this as a base for the front faring:

Amazon.com

 

[The Toecutter]

I would also add.... a decent quality 'bicycle' dual rotor front hub w/precision ceramic bearings and an chromoly axle, will more than survive 60-70 mph punishment.

For how long? That is a great video for demonstrating the durability of DH bike components, btw.

 

[The Toecutter]

The torque sensor, with the CA3 supplying 2x human power input to the electric motor, has increased range at 30 mph to about 40 miles.

That's not bad considering how terrible the aero drag of this thing is.

I think upwards of 60 miles range is possible with same aerodynamic work on this small battery with some pedaling effort.

 

[The Toecutter]

I am in the process of spotwelding up a new battery that can fit in the triangle, so I can free up the rear touring rack for storage space and improve weight distribution by getting rid of the unspring weight posed by having 9 lbs of battery in the back.

A 13S4P 46.8V 14AH pack of Panasonic NCR18650GA cells and a 13S 30A continuous BMS will fit. I plan to run the pack at 32A max discharge, or 8A per cell, which will give 1.5 kW continuous.

Attached are pictures of the cardboard template I made.

 

[Papa]

I am in the process of spotwelding up a new battery that can fit in the triangle, so I can free up the rear touring rack for storage space and improve weight distribution by getting rid of the unspring weight posed by having 9 lbs of battery in the back.

A 13S4P 46.8V 14AH pack of Panasonic NCR18650GA cells and a 13S 30A continuous BMS will fit. I plan to run the pack at 32A max discharge, or 8A per cell, which will give 1.5 kW continuous.

Attached are pictures of the cardboard template I made.

I currently have a '99 FS Diamond FXR DBR I'm converting for family member. I'm installing a fabricated rear swing arm (from steel) which will extend the wheelbase about 6". It'll ride on pair of 406s & 152mm cranks. This will open up the area between the rear tire and front derailleur/BB post - enough for a sizable battery. Thinking maybe a pair Grin hubs or a solo GMac. The idea is a 20-23 mph climber that resembles a cargo hauler

 

[The Toecutter]

I don't have the new battery finished or ready to use yet, but I did do some more efficiency testing.

I dropped the pedal assist to 1x rider input in effort to increase the proportion of energy provided by the rider and my cruising speed is closer to 25 mph instead of 30 mph as a result. Yesterday's 15.9 mile ride resulted in 252.1 Wh used, and 15.9 Wh/mile, with some throttle use of 750W for hill climbs with pedaling added.

 

[Zambam]

You will have to try it and see. I'll make an educated guess and say that a 10-20% reduction in energy consumption is possible with only a front faring, properly placed. You'll lose out on cooling of the rider in hot weather.

I will probably never get to install it. I seldom get near 20 mph around here. If you are interested, you can have both for free. Just pay for the cost of shipping.