Specialised Crosstrail conversion

[Unseen]

I’d like to look at converting my old work commute bike so I can get back to cycling in and get fit/lose some weight. This time of year would be mainly road use but could be tow paths. Around 18mile round trip depending on route. Tried to do it recently and admit I was embarrassed how long it took! Especially when I think to when I did it a few years ago in half the time and smoked!! (Quit them 4yrs ago... Vape like a chimney though lol!)

So the specialised crosstrail I’ve got is 700c wheels, cable disc brakes, lock out on the front forks so all pretty standard as it came.

Thinking about the Q128? rear hub motor, partnered to a 48v battery.

The questions I have are would that wheel/motor combo cope with a chap who’s currently 21st 8lbs? What ah battery would be recommended for around 25-30 miles of assisted use?
I’m not looking for land speed records just would be nice for the average speed to be in double digits! (Yes the test commute was THAT bad)

Thanks in advance!

 

[Deleted member 4366]

Your weight makes it a bit tricky. I think a Bafang CST motor would be better, but it it's not so easy to get one with the right speed. MXUS make a clone of it, which is OK. You could email them to see if they'll put a kit together for you. I think they will because they sell kits as well as the motors. This is the motor you want, ideally with about 260 rpm at 48v.

http://www.mxusebikekit.com/proshow.aspx?cateid=68&productsid=198

Basically, you want this kit, but the XF01C instead of the XF15 with the Dolphin battery.

http://www.mxusebikekit.com/proshow.aspx?cateid=135&productsid=257

If only Woosh had got the cassette version of the motor with their kit. Everybody now asking has cassette bikes. Fitting a freewheel motor brings some complications to the gear system. You can get round all the problems or even live with them, but it does spoil your bike a bit.

 

[Unseen]

I did wonder if the weight might cause an issue... I assume the MXUS/CST have a bit more get up and go in them than the Q128?

I did look at the new @Woosh kit but I don't think I saw the option for a 700c?

What kind of AH should I be looking for @d8veh with the MXUS motor? The route options for the ride to work aren't very hilly, in fact only 2 hills the entire thing, mostly flat or completely flat if I go via towpaths..


Shame really as the other option was the one in the classifieds but I'm guessing front hub motor would end up losing traction a lot more with my weight being more at the rear?

 

[Deleted member 4366]

The problem is not so much the traction, but the torque needed to acellerate your mass. You need a very high torque motor. Another good option might be the 250w 25 amp BBSxx crank drive. Was it Brighton Ebikes that had them?

The battery is a difficult one because you're balancing cost, convenience and size/weight. At 48v, a 12Ah will probably be enough as long as you don't ride with full power everywhere. 14Ah would probably be ideal.

 

[Unseen]

I take it going down to 36v (seems to be the popular figure for some kits..) would make the situation worse and not have enough oompf to get the mass (me!) moving?

As for full power, I'm not expecting to use full power often or at all... Yes I'd like the throttle there for occasional use but the main goal will be just in assist mode with me dropping the assist level as my fitness/weight improves..

I've looked for the BBSxx cranks but when you do find them seems the price for them is considerably more than hub drive.. Don't think I found anyone in the UK with them..

 

[anotherkiwi]

http://wooshbikes.co.uk/cart/#/category/uid-4/cd-conversion-kits

 

[Nealh]

Eclipse.
Brighton ebikes.

 

[Tabs]

I take it going down to 36v (seems to be the popular figure for some kits..) would make the situation worse and not have enough oompf to get the mass (me!) moving?

As for full power, I'm not expecting to use full power often or at all... Yes I'd like the throttle there for occasional use but the main goal will be just in assist mode with me dropping the assist level as my fitness/weight improves..

I've looked for the BBSxx cranks but when you do find them seems the price for them is considerably more than hub drive.. Don't think I found anyone in the UK with them..

I'm the same weight as you and I fitted a 36v 250w kit to an old GT mountain bike and it does the job fine,Am happy with it although I've nothing to compare it to cause it's the only ebike I've ever tried.

 

[Unseen]

Eclipse.
Brighton ebikes.

Both seem to out of stock until the new year...

I did see whoosh and I’ll be honest was put off by the additional cost over hub drive, Plus the loss of the additional gears I assume the cd motor compensates for that?

 

[Unseen]

I'm the same weight as you and I fitted a 36v 250w kit to an old GT mountain bike and it does the job fine,Am happy with it although I've nothing to compare it to cause it's the only ebike I've ever tried.

Ah brill! Which kit did you fit? How do you find it, does it cope with ‘load’ ok or would you say it might feel like it’s struggling?

 

[Tabs]

Ah brill! Which kit did you fit? How do you find it, does it cope with ‘load’ ok or would you say it might feel like it’s struggling?

I fitted a kit from EBC,it cost £420 complete including delivery,I cycle to work with 2 younger guys and I can keep up with them no problem(I usually ride in level 2 of 5)but when it comes to the hills(there's a couple of nice ones)they just can't keep up with the ebike,as an introduction to ebikes I can't really fault it and if you take your time and make a neat job with the wires it looks ok as well.

 

[Deleted member 4366]

You have to be careful with other people's assessment and opinions because their situation can be completely different.

Some people will tell you how their Gtechs fly up hills, but they forget to mention that they weigh only 50kg.

I can tell you that there's not many ebike systems that can deal with a rider that weighs 137kg. I used to weigh 100kg, and you really need a high torque motor for that. Your average 250w hub-motor kit will not be sufficient. You need something like an Ezee motor, Bafang BPM/CST or a MAC. A crank-drive may be OK, but that's a lot of strain on the drive train, so I can envisage reliability issues there.

 

[anotherkiwi]

Ah 137 kg... Didn't get that bit...

A GSM will do the job, it works for cyclists because you have to understand gearing correctly for the road ahead. Non cyclists are better with a hub motor.

You will want to mount a 32/34 tooth chainring to begin. As you lose weight and get fitter just increase the size of the chainwheel.

 

[Unseen]

Sorry yes should have put the weight in ‘new money’ 137kg rather than my weigh in figure, I blame slimming world they still work in stones and pounds!

I hadn’t looked properly at mid drive purely down to the extra cost and it seemed the consensus here seemed to be hub drive. Having watched the Luna install video it seems pretty straight forward, I guess the first question is do I go for 250w or 500/750? (Price between the last two is pennies on some sites) and do I stick with 48v or go for 36v baring in mind the plan is once built to build up to cycling in to work everyday where possible.

I had budgeted around 500ukp for the conversion but if this is likely to be a better option then adding a it more to the pot won’t be too much of a problem.

 

[Deleted member 4366]

I would use a 48v system with a large geared hub-motor. The motor should have a slow winding - something like 201 to 260 rpm at 48v.

A crank drive will work, but I have some reservations about the reliability.

 

[Unseen]

Well I haven't given up searching for a kit (I won't say the perfect kit as everyone has their own ideas of what is perfect!) had hoped there might have been some black friday deals but unfortunately not.

I still haven't tracked down the MXUS motor d8veh suggested in the second post, google comes back with a lot of russian and possibly swedish sites.

I did look at em3ev but blimey I think I was choosing the wrong options there as they seemed pretty costly (before I'd even got to shipping).

I know we mostly only ever use the net to complain but are crank drives that unreliable? Watching some of the bonkers things Luna have done with the bafang CDs made me wonder if reliability is that bad?

 

[Deleted member 4366]

I still haven't tracked down the MXUS motor d8veh suggested in the second post, google comes back with a lot of russian and possibly swedish sites.

I gave you the link. You get it from MXUS. Just e-mail the girls there, and they'll see you right. They're lovely people to deal with.

 

[Unseen]

I gave you the link. You get it from MXUS. Just e-mail the girls there, and they'll see you right. They're lovely people to deal with.

Ahh! Doh feel like a right dunce now! Was looking for a store or something, didn’t think to email them direct! I have looked at a few other kits unfortunately I left the links at work to see if they may be as good?

 

[Woosh]

If only Woosh had got the cassette version of the motor with their kit. Everybody now asking has cassette bikes.

I have the DNP screw-on freewheel 8-speed 13T-32T, it solves most of these problems: low lost, high torque, simple tooling.
I also have rear 36V BPM code 13 on 700C rim and 20A controller, not the HL version because it can't take 9 FETs, but the LS947 that mounts onto the seat tube like this:

I can supply this kit with 15AH HL battery for £599.

http://wooshbikes.co.uk/?hubkits

 

[Unseen]

Sorry for not replying to this thread sooner, work and the usual home "DIY" before christmas requests got in the way...

Based on that kit @Woosh I assume it should be ok with the 'load' it's going to have to shift? Based on bike and assuming kit is roughly 6kg it's going to need to assist 157Kg (well a bit less been good on the old slimming world of late!). Is the controller you mention a sine-wave controller?

Would I realistically be better trying to put together a 48v system which going off the various other build threads here seems to be the general recommendation or would the loss going to the 36v system not be much I guess based on the weight/load it's having to move?

@d8veh I did try to email MXUS directly with the link off their website but it bounced back as undeliverable, do you have an alternative email address for MXUS or would I be better going via I think Alibaba?

Curious to see what price it would come back although there is a massive pull to buying it all locally so to speak so if I did have any issues there's potentially someone at the end of a phone at a reasonable time.