Titanium Fatbike - Bafang Ultra and Phaserunner

[Daxxie]

How long are those chain stays?

Chainstays are 500mm

[*] If you don't mind could you repost the first image (bike geometry) in your opening post again in higher resolution?

I've sent you a PM

Is there anything you would change about the frame if you could start from scratch, would you for example stiffen up any part of the frame given the high torque motor?

Stiffness:
Titanium is not very stiff. It is strong and quite flexible wich gives you a lot of comfort on the bike.
Imho it's a good choice for a fun fatbike.
The motor mount is a bit overkill. It's very beefy and I think they could made it less thick and save some more weight there.

Size:
My old fatbike had a medium frame 17" and always felt a bit too small.
So I went for a large frame. But this one is a bit too big. I would go for a 470-480mm frame next time.

Chainstays:
I would go for a shorter chainstay, I think they could make it another 2 or 3 cm shorter without tire clearance problems.
This would probably make the handling a bit more agile.
Also a standard chain doesn't fit the bike. I always need to add 4 links to a standard chain.

Next build?
Love this bike but a Rohloff hub and a Gates belt would make this even better.
Or a full suspension Fatbike frame....

What is the total weight of the bike with the battery and motor (48V 14Ah?), around 23 Kg?

Without battery the bike weighs 17kg!

 

[El_Topo]

I've sent you a PM

Thank you again, it is very much appreciated!

....

Thanks for the detailed answers!
It will take some time for me to process all this.

 

[Boondocksaints]

Daxxie - you are a beast!

I was also considering a Titanium frame with my build, but was concerned about the durability due to the flex. Do you not see this as a concern?

 

[Daxxie]

I was also considering a Titanium frame with my build, but was concerned about the durability due to the flex. Do you not see this as a concern?

No, not concerned at all.
Ti flexes but can withstand that flex much more then other materials.
Also makes the bike more comfortable .

The frame was designed to take the Bafang G510 and a battery.
It's not a standard bike frame.
The motor mounting plate is from a quite big solid piece of Ti.

And compared to a carbon fiber or alu frame it can be repaired much easier.
It never corrodes and always looks nice and shiny.

 

[Deafcat]

Love this bike but a Rohloff hub and a Gates belt would make this even better.
Or a full suspension Fatbike frame....

Nahh dude!

Rohloff adds a ton of weight to the rear which throws off the balance. Huge cost spike as well.

Belt drive adds frame complexity (open triangle requirement), tensioning requirement, and reduces efficiency versus roller chain.

Full suspension adds unnecessary weight, cost, maintenance, to an already supple fatbike with a flexible titanium frame. Who needs more compliance over that?


You've got a great setup, be glad with it

 

[Boondocksaints]

I was also considering a Titanium frame with my build, but was concerned about the durability due to the flex. Do you not see this as a concern?

No, not concerned at all.
Ti flexes but can withstand that flex much more then other materials.
Also makes the bike more comfortable .

The frame was designed to take the Bafang G510 and a battery.
It's not a standard bike frame.
The motor mounting plate is from a quite big solid piece of Ti.

And compared to a carbon fiber or alu frame it can be repaired much easier.
It never corrodes and always looks nice and shiny.

Thanks you for your input. I'm inspired now - heh.

Probably not as custom as yours, but I think I will definitely be going the Titanium route.

 

[El_Topo]

May I ask a few more things if you don't mind?


If you would thicken the chainstays, there would be less flex, right? I am asking because I am concerned that the flex might interfere with narrower cranks needed for a small Q-factor as there will be obviously less space between the crank arm and the (flexing) chainstay.

What do you think about adding sliding dropouts (second photo behind link) to be able to shorten the "rear axle to crank spindle distance" (what is the name for this, just "chainstays"?) for a more manoeuvrability or to lengthen it when desired like riding in the snow or longer tours - also to accommodate tires with varying diameter?
The Otso Voytek does this and from what I've read it seems like a good idea.

What do you think about angling the motor mounting plate a few degrees more upwards to bring it more in line with the down tube? I think what would make for a slightly more pleasing design.

Would an IGH like the Rohloff allow for a different chainstay design, given there will be no need to accommodate for todays huge 500% cassettes?

The battery mounting plate that you attach to the downtube, is that a standardised format, meaning the screw holes will be in the same place and have the same distance to each other for all standard* battery packs?
It would be bad to have the screw holes drilled by the frame manufacturer to have the bottom of the mounting plate not clearing the motor mount because you haven't decided what battery pack to get at the time you approve the final frame design or when you switch to a new battery pack in a couple of years.
In General, are there ways to secure the battery mounting plate better to the frame? I am a bit worried that a 5kg battery is only held by 4 screws when riding at higher speeds in rough terrain.
What you think about asking the frame designer to flatten the down tube where the battery is attached to provide for a stronger connection between the mounting plate? Any downsides to this approach (if possible to manufacture)?

Also, you have another display than the "DP C18.UART", is that because of the Phaserunner, meaning you can't use the original Bafang display (because of the higher Watts/Amps)?

Thanks in advance!

PS: Why not add the photos from the Bafang Ultra thread to this, so other interested members won't miss them?

*I am aware that standards can and will very likely change...

 

[Daxxie]

If you would thicken the chainstays, there would be less flex, right? I am asking because I am concerned that the flex might interfere with narrower cranks needed for a small Q-factor as there will be obviously less space between the crank arm and the (flexing) chainstay.

Yes, bigger tubes would mean less flex. But the flex is mainly noticeable at the back of the chainstays, not where they are mounted to the motor mount, where the pedals are.

What do you think about adding sliding dropouts (second photo behind link) to be able to shorten the "rear axle to crank spindle distance" (what is the name for this, just "chainstays"?) for a more manoeuvrability or to lengthen it when desired like riding in the snow or longer tours - also to accommodate tires with varying diameter?
The Otso Voytek does this and from what I've read it seems like a good idea.

-more complex
-heavier
-more expensive
-but nice to have!

What do you think about angling the motor mounting plate a few degrees more upwards to bring it more in line with the down tube? I think what would make for a slightly more pleasing design.

Around 10° would be possible with this motor mount.

Would an IGH like the Rohloff allow for a different chainstay design, given there will be no need to accommodate for todays huge 500% cassettes?

No not really. You would need the Rohloff XXL which is 190 or 197mm
For more pedal clearance it's mainly the tyre you want to acccomodate that determines the width of the chainstays

The battery mounting plate that you attach to the downtube, is that a standardised format, meaning the screw holes will be in the same place and have the same distance to each other for all standard* battery packs?
It would be bad to have the screw holes drilled by the frame manufacturer to have the bottom of the mounting plate not clearing the motor mount because you haven't decided what battery pack to get at the time you approve the final frame design or when you switch to a new battery pack in a couple of years.
In General, are there ways to secure the battery mounting plate better to the frame? I am a bit worried that a 5kg battery is only held by 4 screws when riding at higher speeds in rough terrain.

No, the screw holes are for the Hailong Jumbo case.


Smaller Hailong case might also fit.
On my other bikes I used to fit my Hailong cases with the standard 2 screws.
That didn't work really well. Too much vibration and sooner or later the cases broke.
Since I changed all my bikes to 4 screws (+ 4 rubbers under the screws) the cases are rock solid and last a long time.

You really have to consider which battery(s) to use first before ordering a frame.
I wanted a custom made battery from the beginning and only added the 4 mounting screws as a temporary solution to mount a Hailong case. The 4 screws are also intended for mounting my custom battery.

What you think about asking the frame designer to flatten the down tube where the battery is attached to provide for a stronger connection between the mounting plate? Any downsides to this approach (if possible to manufacture)?

If it looks good and doesn't compromise the strength of the frame, go for it!
I like the integrated battery much more but would be more difficult to make

Also, you have another display than the "DP C18.UART", is that because of the Phaserunner, meaning you can't use the original Bafang display (because of the higher Watts/Amps)?

Yes, that is a Cycle Analyst.
It doesn't look so good I know but you get used to it
Gives a lot of usefull information and you need it to be able to tweak and program the Ultra

https://www.ebikes.ca/product-info/cycle-analyst-3.html

 

[navasjm]

You really have to consider which battery(s) to use first before ordering a frame.
I wanted a custom made battery from the beginning and only added the 4 mounting screws as a temporary solution to mount a Hailong case. The 4 screws are also intended for mounting my custom battery.

Where did you get that custom made battery? It looks really nice.

Thank you so much for your post, you helped me to decide, now I´m planning to build a similar bike to yours, I´m already chatting with Linda for the frame, and I´m gonna try to get the Bafang Ultra in the other page you recommended. I really don´t know what battery should I buy for this project, I don´t have any experience with e-bikes; I was considering this one:

https://em3ev.com/shop/em3ev-52v-14s5p-jumbo-shark-ebike-battery/


When you say you installed the gear sensor in the down tube you mean inside the downtube? your bike looks so clean with the internal cable routing.

This is gonna be my first Ebike and I think the ultra is the best option since it has the torque sensor and I really like to pedal.

If you have any other tip for me I appreciate it.

 

[El_Topo]

Thank you again for the reply, Daxxie!

Yes, bigger tubes would mean less flex. But the flex is mainly noticeable at the back of the chainstays, not where they are mounted to the motor mount, where the pedals are.

Good to know, thanks.

...sliding dropouts...

-more complex
-heavier
-more expensive
-but nice to have!

That is what I thought!

Yes, bigger tubes would mean less flex. But the flex is mainly noticeable at the back of the chainstays, not where they are mounted to the motor mount, where the pedals are.

Good to know, thanks.

Around 10° would be possible with this motor mount.
View attachment 5

Thank you for the Photoshop mock-up. It looks good, doesn't it?

... IGH ...

No not really. You would need the Rohloff XXL which is 190 or 197mm
For more pedal clearance it's mainly the tyre you want to acccomodate that determines the width of the chainstays

Thank you for the explanation.

... battery stuff...

Thank you for the explanation.

I like the integrated battery much more but would be more difficult to make

I do too but with those proprietary designs you never know if you can another battery in a few years down the road which is easy if you have one of those standard Hailong battery cases or a custom case where you can just get new (sized) cells with higher capacity in the future.

Yes, that is a Cycle Analyst.
It doesn't look so good I know but you get used to it
Gives a lot of usefull information and you need it to be able to tweak and program the Ultra
https://www.ebikes.ca/product-info/cycle-analyst-3.html

Thanks, will have a look at this device.

 

[El_Topo]

Where did you get that custom made battery? It looks really nice.

I was about to ask the same.

Thank you so much for your post, you helped me to decide, now I´m planning to build a similar bike to yours, I´m already chatting with Linda for the frame, and I´m gonna try to get the Bafang Ultra in the other page you recommended.
...
This is gonna be my first Ebike and I think the ultra is the best option since it has the torque sensor and I really like to pedal.
If you have any other tip for me I appreciate it.

Great to hear! I would be interested in your build as well, so please keep us updated and let us us know how everything progresses. I *just* told Daxxie, how helpful his thread is for others!

Maybe open a new build thread for this, so others can follow your planning and build?

 

[Xander02]

Hi Daxxie, loving this build. I would like to do similar but use my existing 29” wheels.

Would 29” wheels fit on this fat bike frame’ i.e is there enough clearance?

Thanks

 

[fechter]

What size chain ring are you using?

 

[SNOW JW]

What did the frame cost & time to ship?

 

[bafang1500]

Hello, I use a Bafang Ultra Max 510.000 with a 1000w battery on an aluminum frame.... the weight is over 20kg, I would like to know if it is possible to use a titanium frame, where to find it, how to go about it?
See picture attached
Thank you

 

[Daxxie]

Hello, I use a Bafang Ultra Max 510.000 with a 1000w battery on an aluminum frame.... the weight is over 20kg, I would like to know if it is possible to use a titanium frame, where to find it, how to go about it?
See picture attached
Thank you

Yes you can use a Titanium frame but your end result won’t be much lighter. Maybe 500gr less.

 

[Daxxie]

What did the frame cost & time to ship?

800usd + shipping.
Took around 50 days (chinese newyear included)

 

[Soren0105]

Daxxie, what a great build!
I'm about to order a frame like yours except non-fat off ali but with the Chinese new year and the delayed reply times there's lots of time for surfing for other's experiences.
I'm wondering how long you've driven your build by now?
Are you satisfied with the quality of your frame?
And maybe you already answered this: what are the largest battery dimensions you can fit in the frame?
Kind regards
Søren
Aarhus, Denmark

 

[Daxxie]

Daxxie, what a great build!
I'm about to order a frame like yours except non-fat off ali but with the Chinese new year and the delayed reply times there's lots of time for surfing for other's experiences.
I'm wondering how long you've driven your build by now?

Been driving it for over a year now.
I love the frame and the Bafang Ultra

Are you satisfied with the quality of your frame?

Yes and no! The rear was quite flexible and that is very comfortable but last september one of the chainstays cracked.



So I contacted the manufacturer who was very helpfull.
Frame was send back to China and professionaly repaired by them.
They replaced both chainstays with "thicker walled" tubes.
According to them all newer frames will have this thicker material.
Sending back repairing and shipping back to Europe costed me a month downtime and around 60€

And maybe you already answered this: what are the largest battery dimensions you can fit in the frame?

At the moment I'm running the poly shark case with 90cells capability and that fits fine.
Still designing a bigger battery case that will hold 100 cells.

 

[Daxxie]

What size chain ring are you using?

42T currently. A 44T would also be a good choice if you like speed.

 

[john61ct]

The Brompton knock off is the only frame I see there now

 

[Tommm]

At the moment I'm running the poly shark case with 90cells capability and that fits fine.
Still designing a bigger battery case that will hold 100 cells.

They do one off frames made to order? What price?

 

[Soren0105]

What size is the head tube?
When I ask questions on alibaba they only answer the first one :lol:
And did you have any thoughts on the gear hanger not being interchangeable?
I mean if it should bend you might not be able to mend it?

 

[Aerialpixels]

Did you get that jutter ironed out? My BBSHD / Phaserunner on 88v on Khs 650 6500 full suspension frame had way more flex than that and if you ask me, the problem isn't related to the frame. That looks like a complete auto tune hickup. I've had my motor behave like that while tuning and the bike off the ground and no chain on. I selected "enable level 3 access" reloaded bbshd file from grin and saved.
Problem went away on the next auto tune. There is definitely 100% so weird things that can happen while tuning that I cannot explain but have experienced many times. For example, I bought a new phaserunner and just loaded the working file from my old one phaserunner. Motor wouldn't even turn.
I've also played with KI and Kp for days trying to get rid of instantaneous over current faults only to find that restoring everything as described above and starting over solved it. I think. Many setting affect other parameters we don't have access to.
Just changing system voltage in the software will screw the whole auto tune up to no end.

 

[Daxxie]

Did you get that jutter ironed out?

By dropping the Wgain value in "Throttle power mode" the jerking (oscillation) goes away but it does make the bike a bit sluggish on startup.
Better for the drivetrain or for unexperienced drivers but sometimes I would love a bit more power from standstill.

Maybe I should try to autotune it again.