DonnieD

I've had a bike for a few years now and recently started using is as my main transportation (got sick of late and expensive buses). Its a matts TFS 700, like this one pictured here: https://s.sbito.it/images/16/1619332739.jpg

Anyway I travel 9 miles each way on this to work and I'm managing the journey fine. However I'd like to shorten the time its taking me to get to and from work, especially getting back home as I often finish at 10pm and its mostly up hill on the way back, so it takes me over 50 minutes (especially after a tiring 10 hour shift).

I decided I'd like to upgrade the front wheel to electric. Nothing powerful, just enough to assist my pedaling to speed things up a bit, would be great if I could pedal just the same as I do now but get home in 30 or so minutes rather than 50+

So I had a quick look on Amazon.co.uk and found some kits between £200 and £250, mainly Barsoom 36V 500W kit and a Sainspeed 36V 250W, both get good reviews from customers and considering I don't want anything special at all I assume either of these will be ok? Of course I'll look around more before deciding what to buy, but just wondering about these kits as a base line.

However I was wondering will there be any obvious problems fitting these kinds of kits to my bike in particular? Also do these kits have any problems with rough terrain? On my way to and from work I have to go through two woodland areas. Both reasonably well taken care of paths for the most part, but they do still have some bumpy and potted sections and I was wondering if the motor on these kind of kits could have problems with being jarred on these kind of off road paths?

Thanks for any advice you can give.

sculptingman

I would avoid a front wheel motor of you need it for uphill...

Either a rear wheel motor, or go for the best option available... A Bottom Bracket motor.
the beauty of a Bottom Bracket motor is that it channels the motor's power thru your rear gear train... Allowing you to get maximum motor torque on any terrain thru use of all those gears.

since you mention Pounds... You are in Britain? The only downside is that you may have pretty strict limitations on what power of motor is legal... However, I can tell you that a 350 watt BB motor is far more powerful than a 500 watt hub motor.... Because of the available gearing.

Bafang makes a 350 and a 750 BB motor that can be installed on almost any bike with a standard Bottom bracket shell. With a down tube mounted battery... This solution keeps the center of gravity on the bike very low, and results in much better handling.
the motor would replace your front chainrings.... But I think you will find that with 9 pedal assist modes to choose from, ( and a Throttle ) that you won't much miss the front chainrings. Just pick a front chainring that gives you the minimum low end torque you need with your lowest rear gear to make it up your route... And a good spread of sprockets on your rear cassette to your high gear.... And you will find the combo of rear cassette, and 9 pedal assist settings will be a far more comprehensive range of gearing options for you to select the precise amount of effort you want to contribute.
with enough battery... You may find you can motor all the way home when you are too beat to pedal.

DonnieD

I had considered a rear wheel kit because as you say it should be better for hills, but I thought a front kit would be easier to install. Since I only want a bit of assistance and still plan on putting in the same effort as usual pedaling (don't want to do less work as its good exercise, just want to go faster) I thought a front kit would be ok just to give me a bit of a push up hill. I know this may sound silly on a cycling forum but while I enjoy riding my bike I don't know much about repairing them outside of the basics so I thought avoiding the gears on the rear wheel would make things easier when installing this kind of kit.

But I suppose I could get a few pointers off a friend and maybe consider a rear kit if its going to be a lot better. Are there any advantages at all to a front kit?

I'm in England yes, I have no idea what is and isn't legal as far as an electric bike, I hadn't consider it. I suppose that's something I should check out, thanks.

sculptingman

The trouble with a front motor is that on the uphill it loses traction... This loss of efficiency is made even worse when your front end is sprung... ( the primary advantage to a hard tail bike is more efficient power transfer )

an additional consideration is where the battery will go... Some kits mounte battery on a rack in back...which is a lot of weight way up high.

the advantage to a BB motor is that its weight is down low... It remarkably easy to install... You literally pull off the existing crankset and slide in the motor, and less power goes farther because of the gearing you can put in the back.
the Bafang has 9 pedal assist settings... So if you want to do more of the work ( and save battery) you just set it lower... But when you are coming home and are tired and want a little extra help...it's there for you as you please. I have to ride up a 20% grade on my way home from wherever I ride and I can keep it rolling at 18 mph on assist level 5... Its a work out... It's just a much faster speed than I ca push up that hill on legs alone.

the other best option for your machine would be a rear hub... But be aware that they come in three kinds... Geared hubs...that might be better for climbing... And straight wound hubs...which can have windings optimized for speed OR for torque. For your use you want torque.
but the downside to a rear hub is that it might mean giving up your gearing in the rear. Or switching to one of the hub motors that have internal gears... Like a 3 speed.

in any event...the problem with rear hub motor is that, even if they allow you a cassette... The only thing that cassette is doing is changing YOUR torque to speed ratio... It has no effect on the power of the motor.

i think of you try out a few BB drive bikes you will rapidly discover that they offer you the best possible combo or power and gear train flexibility.

DonnieD

Thanks for the advice. Checked UK law BTW and its limited to a quite absurd 200w motor... However apparently its never enforced unless you go above the European 250w limit. Anything over and it would need to be registered and insured like a moped, so I'll stick to 250w.

The only thing I'm now unsure of is which battery I'll need, as all the kits I'm looking at don't come with a battery. I know for what I'm getting I'll need 36v (likely 3 x 12v batteries), but what do I need for amps? I'll need to do around 20 miles per day, but I won't be using electric for all of that, likely closer to 10 miles per day with electric assist on. I can charge every day so I'm happy to go with the minimum to allow that, for weight and cost reasons.

FMB42

I highly recommend a LiFePO4 battery over lead-acid types. Lead acid batteries are inefficient, "maintenance prone", and very heavy relative to LiFePO4 types. Imo, the worst of these issues is that LA battery types often must be recharged almost immediately after light to moderate use (i.e. once you get to work, and again once you get home).

Just my 0.02...

Anyway, I'll step back so that sculptingman can continue to help you with his wise advice.

Good luck, ride safe, and welcome to the forums!

DonnieD

Yeah I looked at lead acid batteries first and while they're cheap they just seem impractically heavy. I mean 3 x 12v 10ah batteries is something like 17 pounds from what I can see, plus the added weight of a 250w motor and I'd be adding something like 22 pounds (10kg) or more to my bike. The price is tempting though at only £35.

On the other hand a lithium ion battery looks great when it comes to weight and size, but seem very expensive. Cheapest I can find for a 36v 7ah battery is £250, that's as much or more as I'm planning on paying for the kit itself. Would it be possible to use power tool batteries? For instance link two 18v 4ah makita drill batteries together to give me the 36v? I know that only gives me 144w which would only last about 35 minutes using a 250w kit (?). But to be honest that's probably all I'd need per day and I could get two of those batteries new for £100.

EDIT: Found a 36v 4ah power tool battery new for £75, less than 3 pounds (1.3kg) in weight.

350htrr

Batteries would be the last thing I would chintz out on. JMO A smaller less powerful motor is OK as long as it's just an assist like what you want, but the batteries... Buy the best you can afford...

DonnieD

Ok instead of power tool batteries I'm looking at RC battery packs, as I've seen quite a few people online talking about how they use these kind of packs.

What about two of these lipo batteries?: Gliders G-POWER Lipo Batteries 35C All matched A-grade Cells 1s/2s/3s/4s/5s/6s | eBay

Also I've found some reasonably priced LifePo4 battery packs, unfortunately none of them come in a voltage that easily add up to 36v. Would it be possible to wire two 13.2v LifePo4 packs and one 9.9v LifePo4 pack of the same make and amps together? These are the brand I'm looking at: RC ZIPPY Flightmax 4200mAh 4S2P 30C LiFePo4 Pack | eBay

FMB42

I'd look into a ready to go 36v 10ah e-bike battery. My aluminum cased "on/off" switched 36v 10ah battery was ~ $375 USD. This battery uses a "slide-on" locking rail mount that makes it quick and easy to install and remove.

DonnieD

Ok I'll have to keep looking then and hope to catch a deal on a good battery.

I have another question, this time about the robustness of these kits. Considering I'll be regularly ridding over woodland trails do I need to make sure the wheel I convert has suspension? As in will the motor be damaged by jarring without suspension to take the edge off? Because my bike only has it on the front wheel.

FMB42

Yes, a rear suspension would take some of the jarring off. But you should be OK with a hard-tail (no rear susp.) bike as long as you don't go slamming into serious bumps and the like. One thing is for sure; you'll want a steel framed or steel wheel dropout equipped bike (I do not recommend aluminum framed or aluminum dropout bikes for e-conversions).

As for the hub motors; wide diameter Direct Drive (DD) motors are sometimes laced to rims that are not designed for the excessive spoke angles required due to the DD hub dia. This can result in spoke breakage problems. Geared hub motors do not seem to suffer as much from this due to their smaller hub diameters. However, you will (of course) want to pay extra attention to the spokes of either motor type (i.e. spoke tension and broken spokes, etc).

sculptingman

What problems have you seen to make this recommendation?
i have a converted Spot Ajax... Aluminum frame and carbon fork... With a 750 BB motor...
Thus far I have noted significantly less frame deflection than the pre-converted setup simply because the crank is no longer part of the chainring/spider. That is...the torque of my pedaling is filtered thru the motor gearing resulting in much smoother power and what LOOKS like a lot less stress on the frame...

but then, I have not been running it long... Are there going to be problems I am not foreseeing?
( the Ajax frame has been certified for Gates Belt drive, so I know its rear triangle has been engineered for very low deflection )

FMB42

You're go to go with that BB motor setup! I'm talking about the far more typical hub motor type drive systems that place a lot of counter-torque on the dropouts.

sculptingman

Whew! You had me scared for a moment...
I looked and looked for a bike to convert that would give me both the handling and the look I wanted. And opted specifically for Gates certified frames because of Gates' requirements on minimal deflection.

i actually chose the aluminum Ajax because the massive motor and even more massive battery would have looked far bulkier bolted to the tiny tubes of a light steel frame.
the larger, oblate square section down tube on the Ajax gave a much nicer aesthetic blend with the big battery block.

I also want to go to a Rohloff hub, with gates belt drive for an even cleaner driveline... But the Spot company advises that they have not certified the frame for the Rohloff... Which apparently exerts a massive counter-torque... But I might have to try it anyway... As it's the only IGH that can give me the perfect driveline the gates belt requires...

i posted a picture of the result on the pictures thread... I think it came out pretty clean looking.


as to the OP... If limited to 250 watts I would strongly advise a BB drive. That's not a lot of climbing power, but when run thru your rear gear set, it will offer maximum climb ability for the wattage.
if you must go hub... Go for an internally geared hub. They are noisier, but generally climb better.

DonnieD

Since I'm only going for a low powered 250w motor would counter-torque be much of a problem? Hope not, as far as I know my bike is aluminium.

FMB42

Didn't mean to startle you sculptingman! You're running a "state-of-the-art" machine there...

Donnie; check the axle dropout forks on your bike with a magnet. If the magnet does not "stick" then it's aluminum (of course). Some people do use hub motors on aluminum and carbon-fiber dropouts. However, most hub motor manufacturers recommend against this. Either way, I recommend that you properly install a sturdy "torque arm" so as to reduce the chance of having counter-torque damage or ruin the dropouts (people have had serious crashes because of this). Some builders even use 2 torque arms (one on each side of the axle). Btw many kits come with torque arms, but you can also buy them separately from various e-bike parts vendors.

350htrr

Really? I would say it's steel then.

FMB42

You are exactly right! Glad you caught my mix-up! Thanks...

sculptingman

I should point out that the spot Ajax has steel dropout plates mounted in the aluminum sliding tension bracket. Still not sure why they don't endorse the Rohloff hub for this bike...

DonnieD

Still looking into this. Think I've got a good battery solution sorted, but I'm still deciding on the implementation of the kit itself. At first I was looking at a front wheel kit, as it looks so easy to install. But after advice here, and elsewhere I decided against it. So I decided I'd go for a rear wheel kit, but I've been reading a bit more and have seen people mention potential lock ups with these wheels. Now obviously a rear wheel locking up isn't going to be as bad as a front wheel doing the same. But I can imagine that a back wheel locking up at 25mph on a main road could still quite easily be deadly. So how likely is this to happen?, can't imagine its common, but just how rare is it?

Anyway I started looking at the kind of kit sculptingman advised me to get in his first post in this thread, bottom bracket, such as: New upgraded 36V 250W Mid Drive Brushed Motor ELECTRIC BIKE KIT | eBay

Should be good for up hill and also if it locked up there'd be no problem. Unfortunately I'd lose two of the front gears but I only use the largest anyway 99% of the time.

Delphinus

Do be a little wary of noname kits off ebay. A good kit from a very reliable shop is one of the Bafang units from E-Bike Kits
EM3EV are very helpful and a good source for a battery too.

chas58

I have a commute like yours. A small 250 watt motor (Q100) and 36v10ah LiFePo4 battery gets me 25 miles – which is plenty for an 18 mile commute. Costs about $500.

I used a rear motor, but with only 250 watts, there isn’t much problem putting it in the front wheel. You are right, a small motor like a Q100 does not have enough torque to cause much damage. Bigger than that, I would go rear definitely.

If you only need it for hill climbing, you don’t need a fast motor, just something to get you up the hills at 10-15mph, eh? Something like this would give you an idea: Hill Topper Electric Bike Kit, Electric Bike Batteries: Electric-Bike-Kit.com

I run at about 22mph, and it takes me about 25 minutes to get to work – 9 miles.