NS Suburban street bike BBSHD 78V Phaserunner 21s4p

.Eek

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Apr 13, 2021
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Hello! I would like to share the project I've just started for those that might be keen on following the progress and see how it will turn out.

Recently I've dusted off my old street bike with - similar to a - BMX geometry and 24" wheels, some new rubber and a brake refresh will cover most of the safety issues in it's current state. It's a chromoly frame from 2007 if I recall correctly. Build from scratch and went thru quite some punishment on the streets of The Hague and Rotterdam in the days.

Some of the specs of the bike that is going to be used:

NS Suburban frame
Atomlab handlebars
24" Atomlab rims with heavy duty DT spokes, 32 front, 36 rear, fitted with new Maxxis Holyrollers
Bolt on rear Chris King hub, with metal cassette body, quick release CK up front
Magura MT7 with 200/220mm disks

I've ordered a BBSHD, 52v battery and a box of extra cells, Phaserunner and CA to squeeze it to it's limits and likely a little beyond that ;)

The goal is to create an esthetically pleasing bike, with a clean look. So no cables in sight, nice lines and not much going on in the handlebars area nor anywhere else. Used more as a scooter, but with very nimble handling, fast acceleration and more than decent brakes. Sub 50 pounds would be nice, but that might be a few pounds too much I'm asking for.

I've started to cut away some metal from the frame, so the motor can be mounted horizontally inline with the bracket and also get some more ground clearance. The downtube has also met the grinder, so a plate can be welded in that accepts the battery nicely on a flat surface. I'm a bit worried about the stress the bolts and rivnuts have to bare, when mounted on a round tube, so this solves that potential issue. Cutting away material gives also acces to the inside of the frame, where the wiring can be laid out, and I'll keep acces to it via some ports.
One of the last steps will be to connect the top front of the motor to the downtube, so it will become a structural part of the frame. The questionable bracket that clamps (!?!) the motor to the frame, will be welded as well.

Gearing will be a single speed setup, 30T up front and 12, 13 or 14T at the rear - with 24" wheels - for starters. Might have to change that, depending on the acceleration. 25-35 mph topspeed would be ok without pedaling.

I've attached some pictures of what's been going on till now, and I'm awaiting a Luna 30T sprocket, a singlespeed spacer set and the Phaserunner. As soon as I get some parts in, I'll update the thread.

Cheers!
 

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Some more pics..

Ordered some ABS sheet to shape the new battery housing, so I can prepare a plug for a mold to pull a new carbon/aramid cover from it. Looking into adding some extra tabs to the inside of the frame that attaches to the battery cover, so it will be more crash resistant.
 

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Update! We're almost there.. Just need a bit more tweaking on the CA3 and Phaserunner settings, find the right gear ratio and finish it off with the original decals.. :)

Currently testriding it with 30:15, but looking into 28:21 for better acceleration, combined with the 24" wheels

FC9A1974-8994-4293-9AC6-0D347E9A45CB.jpeg
 
Great bike.

As for the gearing. Bbshd will blow past 35 mph with that phasrunner setup. My Bbs02 did 33 mph max on the stock controller with a 44-14. I am guessing you will easily meet that 35 mph goal.

Good luck, keep us posted with the results!
 
Did you weld up a patch for the part of the downtube you cut away? That's a high stress area of the frame.

What was your rationale for using a single speed BBSHD rather than a hub motor? Just to keep the expensive Chris King hub?

EDIT: Oh boy, most of the downtube and some of the top tube too. Let us know when it breaks.
 
DogDipstick said:
Great bike.

As for the gearing. Bbshd will blow past 35 mph with that phasrunner setup. My Bbs02 did 33 mph max on the stock controller with a 44-14. I am guessing you will easily meet that 35 mph goal.

Good luck, keep us posted with the results!

Thanks, I'll update as soon as I get some testrun footage, but it looks promising, with 30:15 I hit 55 mph (laying flat on the bike), but only starts pulling hard from 15mph, so really need different gearing.


Chalo said:
Did you weld up a patch for the part of the downtube you cut away? That's a high stress area of the frame.

What was your rationale for using a single speed BBSHD rather than a hub motor? Just to keep the expensive Chris King hub?

EDIT: Oh boy, most of the downtube and some of the top tube too. Let us know when it breaks.

Well.. it might tear into pieces eventually, but I've put more 4 mm tick metal back in these areas than was cut away, so I'm not very worried.

The main reason to choose the BBSHD over a hub motor is center of gravity. One of the main goals was to build a bike that handles well, is balanced and is predictable in and out of corners. Putting the weight in the middle of the bike would be a sensible thing to do in that regard. A heavy front motor would be a no go for turning into corners, and in the back it will become a wheelie machine more quickly. It's not only the weight shifted to the front or rear, but the weight is also rotating and will act as a flywheel.
 

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Ready for some gear tweaking... Currently 30:15 with 24", but it might turn out to 28:21 for better acceleration... Planning to make some recorded runs for topspeed and acceleration tests.
 

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