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Mid drive e-upgrade and rear BB crossover

Paul Rowlands2021-06-16 20:38:44

Hi,

 

I, as many am embarking on the e-upgrade.  I've read a lot, been baffled a lot, taken some advice from various suppliers and In principle, I've settled on the mid drive Bafang.  Now come the practical/technical questions and I'm turning to the experts;

 

1 - has anybody done this with the rear bottom bracket where a crossover chain set is in place.  If so, do you have instructions/pointers on what to do?

 

2. if the answer to 1 is no, forgive me for asking this question, but I was asked and found it difficult to explain, but how would you explain the crossover (specifically the left hand side) to someone not used to working with this but who had performed the install where the chain sets were all in place on the right hand side i.e. no crossover?  Please humour me and explain in simple terms.  I have taken these apart and put them back together but not necessarily knowing what the parts are called so, is of interest to me from a learning point of view as well!

 

3. any other advice you may have would be welcomed with open arms.

 

In case it helps, the conversion is to be carried out on a Simmonsohn Stavanger and the reason for upgrade is future proofing as one of us is not quite the same as we used to be!

 

Thanks in advance,

 

Paul.   

 

Colin Smith2021-06-16 21:20:24

Hi Paul

I have today taken delivery of a Befang 750w motor. I intend to instal this in a tandem with cross over configuration.  My initial problem is removing the bottom bracket cartridge. So far soaked in penetrating oil for 3 days without any luck.  In desperation have ordered an impact driver.  Will keep you updated. Any solutions anyone has on bottom bracket please feel free.

Colin Smith2021-06-16 21:27:12

I'm also converting a Simmonsohn Stavanger!

Colin Smith2021-06-16 21:27:12

I'm also converting a Simmonsohn Stavanger!

Colin Smith2021-06-16 21:27:12

I'm also converting a Simmonsohn Stavanger!

Stephen Gray2021-06-16 23:12:50

Colin Smith

 

Try using Plusgas. It is referred to as a dismantling fluid and will be more effective than penetrating oil.

Regards

Stephen

Simon Brown2021-06-17 08:11:08

I don't want to put a dampner on things but I thought UK law was that any motor above 250w requires tax, insurance and possibly a motorcycle licence? That's one of the reasons we can't get the Bosch 400w motor here. 

I hope I'm willing but with checking.

Simon

 

Colin Smith2021-06-17 08:56:40

You are correct.

Martyn Aldis2021-06-17 14:07:10

Paul,

In answer to your question 2, I would just say that the left hand cranks have a single chain ring attached, like a single ring solo right hand crank. Obviously the extra bits on the crank, specifically the spider that takes the ring, just might pass through space needed by a specific motor system.

Does that help?

Martyn

Colin Smith2021-06-17 19:42:30

Paul

I have today fitted the bafang to Simmonsohn Stravanger. No real problem after I removed bottom bracket with impact driver. I've listed minor problems and finish with the more difficult one.

1) You have to remove cable guide from below bottom bracket.

2) Battery does not line up with holes in bottle cage due to bottom down tube bend. I have 1 fixing and a cable tie temporary fix.

3) Original 8 speed shifter was part of brake assembly.  Kit comes with 2 new brake levers with switches fitted. Need another 8 speed shifter.

4) Had to remove cross over chain at front. Fitted to the right hand side. I need to purchase 2 chain sets for right hand side (Original have left hand arms and pedals)

My only concern is with the front chain. Using the original chain sets the chain runs a little toe in. I have moved front bottom bracket (The adjustable, 2 bolts underneath) slightly outwards. Not sure if this is wise or necessary.

Please your thoughts and comments most welcome. Will take more pics tomorrow.

 

Paul Rowlands2021-06-17 19:50:56

Hi Martyn,

 

In respect of my query 2, I think you've answered quite concisely! - Far better than I've been doing at any rate.

 

It seems that your post directed to Colin doesn't appear in the forum thread even though it came out via email.  unless you are able to respond to individuals in a way I'm not aware of within forums.  So, hoping you don't mind but  I have duplicated that post below because I found that response useful as well and this may turn out to be a thread on bottom brackets and installing a mid drive motor.

 

Colin,

 

Did you pick the Stavenger up 2nd hand, or is it a reletively new purchase?  my reason for asking is that mine doesn't seem to want to budge either and this was bought 2019 as new.

 

Also, I was going to query the left hand VS right hand threadas per Martyn's post reproduced next;

 

"

Colin,

Can you explain the problem a bit more? If your set up is a cartridge bottom bracket and the problem is releasing the so called "adaptor rings" that thread into the bottom bracket shell,  I can't see how an impact driver is helpful. You need the correct tool, for Shimano and copies a tool to engages with the internal splines on the adaptor, or for a FAG and relations a tool to engage withe the wavy flange. Recently I had to deal with one very well stuck because the inner half of the threads had been destroyed as it was fitted to the alloy eccentric on the front BB of a tandem. I would have had a lot of trouble holding the tool into the splines if the BB spindle had not been hollow letting me put a quick release skewer right through to hold it in place. The left hand one come out first (normal thread) then the right hand (left hand thread).

Am I barking up the wrong tree?

Martyn"

 

Thanks,

 

Paul.

Paul Rowlands2021-06-17 20:08:56

Hi Colin,

 

Our posts crossed over! - Well done on the install.  I'm not able to see yourpicture as am Blind and hence why I'm not always aware of what things are called i.e. when you listen to videos on UTube, people say put this in here and I often get to work out what 'this' is without knowing its correct name!  Anyway, it hasn't stopped me yet and it all adds to the challenge!

 

So, thank you for your post on the experience;  My thoughts on your points in reverse;

 

Regarding your main concern, I was hoping to avoid losing the crossover and keeping the sync chain on the left.  Within the picture you have shared, Is the sync chain ring (rear bb) inside or out?  The following link from Shelden brown goes into some detail about building a tandem crank set with solo parts, but if you scan through, it comments on the single side drive and may give you some pointers on moving that front chain ring out.  Again, I'm not able to get anything from the pictures, but could you perhaps use a redundant smaller spacer ring to move the chain ring out to the right? (assuming that is the way you need to move the chain based on your comment of adjusting the front eccentric.   I guess something similar to the bling ring Bafang speak about.  https://www.sheldonbrown.com/tancrank.html

 

I think I know the answer, but I'll ask anyway;  When you were in bits, could you see any way of keeping the crossover?  I'm guessing not otherwise you would have kept it!

 

Your point 4; In your current setup,  I'm assuming you've kept the rear bb as was, removing the spider from the left hand side, swapping the original rear sync ring to the right, then at the front, keeping the original parts and just swapped the left and right arms around and are looking to buy new arms?  Would it be possible to remove the left and   right arms, turn the front BB around and replace left arm as left and right arm as right with the spider on the right? Remember, I'm performing guesswork here! - more than happy to chat through if that helps.

 

Your point 3; I know the integrated shifter and brake levers can be a good idea, but hinder when we're trying to do this.  The two options here are to either, as you suggest, swap the brake levers for those that come with the kit and buy a new 8 speed shifter or Befang sell sensors designed for hydrolic brakes, but I see no reason why they couldn't be used on standard brakes.  The sensor attaches to the fixed part of the brake and the magnet attaches to the lever - When you pull the lever, the sensor picks the gap up and cuts the power.  The following site has a pretty good utube clip that shows this (I think the 2nd video).  I guess you can decide based on the quality of the new brake levers Vs the old ones! https://electric-bike-conversions.co.uk/pages/mid-drive-kit-installation-guide


Point 2;  I was hoping not, but half expecting this.  I'm pretty sure you'd be comfortable drilling new holes for rivets, but the link above also gives ideas on the best way to do that (I think the 3rd video).

 

 Point1; finally, I was expecting this because the video installation (also found on the link above - 1st video) shows this exact issue.  I only wish I found this link to the utube videos before Today so I could have shared with you!

 

so, point 0;  please share your thoughts on the above and perhaps most important - Other than a few tweaks as discussed above, Have you tried it out yet and What do you think?

 

Thanks,

 

Paul.

Colin Smith2021-06-17 21:30:20

I tried soaking for several days. I tried some Plusgas as Stephen recommended. Finally purchased from Amazon. Immediately came off. Remember Left side 1st  (RHT) then Right side LHT.

Colin Smith2021-06-17 22:38:42

Hi Paul

Will check those Youtube video's out tomorrow. My wife is Servery Sight impaired, that is the main reason for this project.

This was a 1st attempt, and to be honest didn't expect to complete a near working tandem today. I just plodded on with the existing parts.

When fitting the crankset in the original configuration (Crossover) the chainring fouled the motor casing.  If you are referring to placing a spacer behind the chainring this I  think would certainly stop the assembley fitting snug on the tapered shaft. The chainset on the Simmonsohn is not high spec, all the chainrings are riverted together.

I have limited knowledge on chainring, maybe you can purchase one with a different throw.  The trouble is being on the left side of the bike makes it a specialist part. Chainrings normaly fitted to right hand side so pedal fitting is Left hand thread, moving this to the left would result in pedal unscrewing when riding.

When the motor is fitted to the bike through the bottom bracket the motors shaft sticks out, you screw the bafang supplied chainring directly onto the motor assembly, from this a standard tapered shaft comes through the chain ring. This is the shaft to which I fitted the original crank arm & riveted chainring.

What county do you live in?

Hope this helps.

Paul Rowlands2021-06-18 18:03:37

Hi Colin,

 

First off, I found this in another thread as an option for attaching the battery without drilling any additional holes; Triple bob https://ebikes.ca/shop/electric-bicycle-parts/battery-accessories/triple-bob.html  This is in Canada I think but may give you some ideas if nothing else.

 

With regards to the spacer chain ring, I was thinking more for you on the right hand side front bb to stop the toe-in i.e. if you had a double ring set on that front bb the inner ring would be redundant and the chain would sit on the outer.  I guess it's more expense.

 

How my project was born; I consider myself very fortunate in that I also own a Land Escape road tandem specked with Peter Bird some years ago.  My wife was really an off-road girl and so, I think tolerated my wanting to get out on the open road!  Anyway, health and the like saw her not getting out on her solo much and I started looking around for an MTB Tandem and my wife liked the look of the Simmonsohn and so it arrived!  Like you say, the component quality reflects the cost, but the frame is sturdy enough and looked the part (most important right)  My intention was to replace parts with better as they broke, but I've been surprised how long they've lasted!

 

Based in South Wales of all places, covered in hills and mountains (I'm sure there are more up hills than down!) and the development of retrofit E conversions had me in a dilemma of which one to upgrade.  I have used the Land Escape with a number of Pilots raising money on sponsored cycle rides and made the decision for me as I figured if someone is going to sponsor me, I'd need to put some effort in for the cause and not be electrically propelled along!

 

So, the Simmonsohn it is;  I reviewed front wheel hub and at the time, the coupling of disc brakes and less spokes when converted plus the strain on the forks turned me to the rear wheel, where again, the 36 spoke wheel along with the weight and challenges when changing tyres etc. left me with the mid drive.  I didn't really want to lose the 3 front chain rings or the crossover (talk about cake and eat it!) but think the mid drive is still the best option for us.  That’s what brought me to the forum prior to spending the penny’s!

 

There we have it.

Colin Smith2021-06-20 00:06:40

Good point regarding double ring at front. I think the point is that a triple isn't needed with motor assist. If you have the rear range set properly. Most good spec electric MB's only have a single. The Befang can be ordered with a range of drive sprockets. I'm guessing its going to be trial and error.

Thinking about the triple setup I'm guessing with that being the drive ring, and in my experience the most temperamental when changing gear there may be a good possibility of the chain spinning out, chain flying off or even causing the chain to fail. Just a thought.

As far as keeping cross over configuration I cannot see what is gained, only additional expense.  Personally Not having cross over suits me, I have a combination of injuries that suits a very short left crank (100mm), not possible to get a left hand ring gear crank much less than 155mm.

Colin Smith2021-06-20 00:06:40

Good point regarding double ring at front. I think the point is that a triple isn't needed with motor assist. If you have the rear range set properly. Most good spec electric MB's only have a single. The Befang can be ordered with a range of drive sprockets. I'm guessing its going to be trial and error.

Thinking about the triple setup I'm guessing with that being the drive ring, and in my experience the most temperamental when changing gear there may be a good possibility of the chain spinning out, chain flying off or even causing the chain to fail. Just a thought.

As far as keeping cross over configuration I cannot see what is gained, only additional expense.  Personally Not having cross over suits me, I have a combination of injuries that suits a very short left crank (100mm), not possible to get a left hand ring gear crank much less than 155mm.

Martyn Aldis2021-06-21 12:11:07

Hi Paul,

Yes, I deleted my post when it became clear that the proposal was to create an illicit moped not an electric assist pedal cycle. I don't want to help with that.

Martyn

Paul Rowlands2021-06-21 16:29:43

Hi Martyn,

 

Given I've quoted your post in full, Do you want me to remove my post with that quote in?  Also, it's a shame those going to install a 250W won't bennefit from your knowledge as it does seem quite vast!

 

Paul.

 

Martyn Aldis2021-06-21 21:25:31

Paul,

My post was not very helpful anyway.

Most car drivers have a provisional licence for a moped. If someone takes the legal route and has registration, number plate, insurance and helmet for a 750watt tandem conversion do they have to pass a motor cycle test before they can carry a stoker as they would for a motor cycle pillion? Is it even possible to register an e-moped tandem?

Martyn

Colin Smith2021-06-22 09:51:40

The jist of your post is correct. Above 250w would require registration for use on the public highway including cycle ways.  It is theoretical to register an e bike (some people have done this) the main problem is finding someone to MOT the bike and secondly insure the bike.

You are welcome to air your point of view over the legalities of fitting a larger than legal size motor but remember that as a general point this procedure is the same for fitting any Bafang motor including a legal 250w mid-drive unit.

I am sure many people who ride a e-tandem would argue as to weather the existing 250w limit makes the option viable for use on a tandem or not.  My personal decision was made on the basis of total weight carried, terrain, physical ability and most of all reliability. I personally have no interest in speed.

Martyn Aldis2021-06-22 10:43:00

Colin,

I take the point about the mechanical process being the same for 250w and for more powerful e-moped conversions.

As far as legality is concerned it isn't really a question of point of view. If you go over 250w, to be legal you need to do the whole thing: approval to register, number plate, insurance, approved motor cycle helmet, L plates if on a provisional licence. Once your e-moped is roadworthy and legal you are restricted to roads. No riding on cycle paths or trails.

There are web sites that carry on about the excellence of illegal e-conversions and vendors who sell the kit but there were also those who bragged a lot and made videos and so on about riding fixed wheel with no brakes on the road. They seem to have gone to ground a bit since Charlie Alliston got 18 months in 2017after a woman who walked out in front of him while looking at her phone took fatal injuries.

As cyclists we have a bit of a privilege in that we can maintain and modify our own machines without any strict enforcement of standards but deficiencies can come home to roost if there is a collision or heavy fall resulting in serious injury or death. In that event your machine will be taken by the police for scrutiny and if the bike is clearly illegal you may well be in very serious trouble.

Your last paragraph suggests we can make our own choice on motor power for a tandem conversion. Well, I could choose to take an very old motor car out of a barn and drive it on the road with no MOT, tax or insurance saying that it doesn't matter because it won't go over 30mph. I doubt you would encourage that.

Martyn