Testing a front wheel build

winkinatcha

10 kW
Joined
Apr 8, 2011
Messages
587
Location
Melbourne, Victoria, Australia
Yaaaaaay!

I had the privilege to get another cyclist to test out a front wheel build, running a "vanilla" front wheel drive 24v 500w 26" conversion kit


the Challenge

Mr Tester Cyclist (from now on called MTC) does a 60km round-trip commute, from the foothills of the dandenong ranges to Melbourne on a high-midrange 700c based, road oriented bicycle, using flat bars with barends, 9 speed freewheel and 53 tooth chainring.

I want MTC to test one of my builds. “real cyclist” input is something I have not had and dearly want.

By real cyclist, I mean someone who is competent, confident and a long term regular user of a bicycle (human powered only) for both fitness and transport.

Someone who can assess whether a bicycle is rideable over the longer term, and whether a bicycle fitted with one of my kits adds ANY advantages or positives over a human + bicycle.



Meeting the challenge:

First up I personally know that e-bikes make a positive difference to my riding experience. Particularly from the perspective of being an office worker doing a daily commute, and carrying a few injuries from a hyperactive and risk-taking past :)

My reality tells me that the reason I am happy to do a daily commute of 30km round trip by bicycle is because that bicycle is electrified.

I have done the same commute tens of times by human powered bicycle alone, and I have done the commute hundreds of times on various electric bikes.

So yeah, I KNOW a motor is a good thing, and I also know that with MTC the last 5 or so kms, going home, and entering the hills, are killer, and motor assist here would be pretty bloody good.

To me this meant that the challenge could be boiled down to a simple requirement set. Build a road oriented electric bike that has a powered range of 30km over varied terrain when coupled with consistent human power.

Based on MTC’s commuter bicycle’s gear set, a 53 tooth chain ring and lowest tooth count of 11 on a 9 speed rear free-wheel, means MTC can probably do 40km/hr on the flat, and probably cruise at 35 km/h.
I tried to acheive a 30km/h cruising speed on a vanilla kit build based on an entry level mountain bike, but pedalspeed was really too high for a standard gearset… a lot of energy seemed to go in just turning my legs around trying to keep the bike up to the speed of the motor. Range OK… at least 25 km on varied terrain, with no peddling, but that was at the limit.

My conversion kit wheels come laced in 26″ frames, and this currently limits me in that the electric drive wheel can only be 26″.

A Front wheel build with a 700c, human powered only rear end gave me closer to what I needed for MTC to test a return commute.

the Pocket Rocket morphed from a human powered frankencycle (multiple bikes sourced for parts to build one complete bike) to a road-oriented Front Wheel Electric Drive, rear wheel Human Drive.

In its final iteration, powered by a Ping 24v 10ah battery, I could comfortably ride the Rocket on a 30km commute, the setup was comfortable enough to do it consistently. though a few potential problems were apparent, I’d ridden the rocket a few hundred kilometres without more than the usual fear, rage and unbridled enthusiasm that such activities can induce..

The frame was a 26″ frame, with a 700c fitted to the back. retrofitted forks, To level out the front, and provide suspension (Must be considered for front wheel builds) raised the complete frame by at least a couple of centimeteres, making the bike pretty “tall” IE the pedals far off the ground. That coupled with the smaller fram meant distance between handlebars and seat post was not optimum for my or MTC’s 6ft frames, adequate but not optimum.

The motor and controller, at 24volts, ends up with a max speed at around 27-30km/hr. This is a bit slow for someone who can cruise at 35.

Everything else though had me beleiving that the boiled down challenge of creating a road oriented bike that would provide electric assistance for 30 km had been met.

A few things came together well in terms of battery placement.

A front wheel build meant that the majority of extra weight from the bike to e-bike conversion was in the front. this meant that putting the battery at the back provided a balancing solution.

in my endless search for batteries, battery chargers and battery enclosures, i had managed to come up with the combination of a ping battery and 6A charger that comes with it, a robust and ok looking purpose built for bicycles rack bag and a light weight yet robust rear rack with mudguard capabilities.

Ultimately a mountable, demountable and easily carriable “battery Bag”, with everything you need to plug into the nearest mains and charge the battery. No degree in chemistry or engineering required for use or construction :) .



Results

Met MTC in the carpark of my old work building… gave him the info on how to charge the batteries, and ran away suffering from separation anxiety over the Pocket Rocket…

A few hours later and i get a text.. Mr Test Cyclist is home, and both the bike and he were still powering in the last few hills home (W00t).

Later MTC let me know that the battery had recharged in 45 minutes, meaning he’d used less than half of it’s capacity.

Next afternoon, I met up with MTC in the same carpark, and we went over the ride.

It was OK, the bike had got him through a complete commute.

The bike was definitely heavy, and did not power up to MTC’s cruising speed of 30+, meaning he had to haul the bike’s extra weight at these speeds.

The set up was too cramped, for himself MTC needed the bars further forward and possibly out more (note on his bike he had wider flat bars than on the Rocket).

MTC was looking forward to a better iteration..



Conclusion

Now, I wont lie, if MTC had come at me with a fist full of dollars and said “I need one, sell it to me” I would have been satisfied :)

But bearing in mind all of the drawbacks of the bicycle components behind the build, Ultimately I am pretty freakin pleased with how this particular build, the pocket rocket, kinda sorta coulda met the challenge.

Wheel Size and the complications arising from it need to be sorted when dealing with human powered 30km/h + speeds on 700c bicycles.

Interestingly enough I have just pulled apart a different style of hub motor, a geared unit, which I sourced from a secondhand commercial build… and it is laced into a 700c rim, weighs about half or less than the wheels in my kit, and I reckon would take up to 1000 watts, with a bit of care.

Also have a cheap complete 700c based bike… looks like another test build coming up, and then I unearth my uber awesome butted steel frame racer resto I am doing, pop the hub into that…. Second iteration of the rocket somewhere in the visible future, methinks.

What I do with the rocket now is a tough one... maybe a museam piece in 50 years... :lol:

Joe
 
Your Volts are way too low.
The formula to make a serious cyclist get the Ebike grin is;
1)Fast wind geared mini-motor.
2)48 Volts for 700cc wheel, 52 V for 26" wheel
3)Low current, 15 to 17 Amps for 700CC whl., 15 or less Amps. for 26" whl.
4)11T/with 48T or larger chainwheel.

You want a no-load top speed that is power-limited, not rpm-limited, that will continue to add[diminishing]E-power up to 50 Kph.
 
It's all cool motomech, and i agree with your input, totes 100%.

I wanted to run this build without upping the voltage n limiting the current. basically to get as road oriented a bike as I could, with an out of the box kit.

i have run the exact same wheels/kits on 48 volts 30 amps with but a few minor safety mods and removal of dinky 24v battery indicator. Controller totally unmodified.

I reckon I have sussed out the tech mods required to the controllers to limit current (shunt mod based) this is my next phase of kit modding. Attenuating current, first *2 by removal of one of the internal shunts, giving between 10 and 15 amps max current, then *2 again to give 5 to 7 amps max.

With the latter I can run legal on 36 volts (law limits here are 250w... yada yyada..) as well as providing pretty simple upgrade paths to gratter current (through reversing the attenuating shunt mods, and through upping the voltage.

A lot of what I am doing at the mo is basically trying to find ways to make the Australian legal (max power limit of 250 watts and (ithink) top speed 25km/h,via European e-bike standards) workable with the current stock of kits I have...

I currently have 30 of these kits and need to find them a home :lol:

Tho the Pocket rocket is twice the legal limit power wise, at this voltage it is at close enough to the speed limit. It has a 53 tooth chain ring and lowest tooth gear on rear is 11. Bloody expensive sourcing chainrings... grrr.

It is quite possible that making something even vaguely ev-grinnable at this low powered end is a fools errrand, so I am going for functional and "better than a bicycle" abilities, with EXTREMELY SIMPLE documented ready to go mods to enable kit buyers and possibly my build owners to pursue a simple upgrade path through to 1500 watt surge, to be used I assume for purely legal (ie off-road in Australia) situations.

running around on-road with builds with 24, 36 and 48v iterations I reckon 36v/10s is the sweetspot real world, fit cycling speed wise. Rougher terrain, unless yer going for dirt bike level speed, 24v is actually purty darn good, and in both situations I really am assuming human pedal input to make the builds worth while. This is not the normal e/s builds as I am not going down the uber performance route yet, more towards legal-ish safe, plug n pay-ish.

However have run 48v at 20 + amps with top speed 45 kph... about 35 for the 36v...I am looking at getting these things in the hands of new e-bikers, and my PERSONAL opinion is more than around 40kph and I reckon get yourself a motorcycle licence (even a learner's permit) and get some skills on the road BEFORE you go hell bent on a 50kph capable bicycle... Personal opinion only... I've been on motorbikes for 30 odd years, I am soooo very grateful for that experience when operating higher powered builds.

I seriously got to get on to modding a test controller and gettng some miles and results from it...

sooon sooon...



more info about the kits is in the For Sale section under "24v 500w hub motor kits for sale" or similar title... Dohh forgotten the exact words..

Thanks for your input mate :)

Joe
 
Depending on the winding of the motor, "enough" voltage can be anything from 24v to 100. If this kit was intended for 24v, chances are it's a faster winding. All that really matters much is that you have sufficient wattage to reach your desired speed.

Front hubs are handy, since you don't have to make any changes to the chain gearing. I find 48-11 gearing to be a highe enough gear for me to pedal comfy at 25 mph/ 40 kph.

The beauty of the motor is obvious, you can ride a much heavier and more comfortable bike but still only pedal out 50w resulting in arriving only sweating as much as being outside creates. Less really, with the wind drying your sweat the bacteria don't grow in it, which is the cause of sweat stink.

Here's my commuter. Big and heavy yes, so not road bike like at all. But very comfy for me to ride. Even with my destroyed lower back, I can do a 60 miler if I want to on the weekends. Daily commute is 30 miles total.
 
Awesome Dogman, and am always rapt to read your posts.

Definitely can now see the advantages of front wheel in terms of maintaining existing chain gearing, or taking advantage of readily available higher quality gearset components to take advantage of the human power component, and you are right, 48-11 is still OK to match an electric wheel speed of 25mph/40kph.

And the whole weight distribution thing, of being able to carry good weights of 20+ kg on the back rack is a huge advantage.

My main concern STILL with the front builds is strength of fork, personally in this build I reckon I am pretty much maxing out the stress I would put on a cheap steel fork as I have done on this build.

On your commuter, they are some purty sweet looking forks :)

Joe
 
I have a low speed wind 9c front hub motor on the tandem I ride with my gf. I'm running 1400watts peak with one ebikekit torque arm. I took the bolts off yesterday and didn't see any stress marks on the fork dropouts or torque arm. The tandem is a $220 walmart Pacific with a cheap steel fork.

Now I have no worries about going WOT from a dead stop. It really helps to get us going vs babying the throttle.

If you do a good torque arm on steel forks and don't run crazy, I think you're fine.
 
Good to hear re the dropouts VeloMan, but must confess my concern is more for the ability of the Cheap-assed forks to with stand the added weight and power pressures on the stanchions, IE how much back and forward slop may result over time due to forces transmitted on the inner and outter tubes.

on my "test Commuter" a rear wheel build I have some quality rock shocks on the front end, and there is purty much zero back and forth slop, on the cheaper fork builds there seems to be a couple of millimetres of slop (forward/back movement with front brakes on) even with new outta the box cheap-assed forks.

How that slop manifests itself over time and battering is my major concern.

Joe
 
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