MBB lowracer

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   MBB lowracer build.  I’ll
do a full write up of this for the magazine, but in short:

I’ll set my stall out from the outset – I’m trying to build a
moving bottom bracket (MBB) lowracer that I can add a rear fairing to, which
will be fast enough to play with the ratracers next year in ‘part faired’.  I think that the Nocom is not efficient in
transferring pedalling input via the long chain & idlers to the rear wheel,
hence my desire to experiment with a very efficient, short drivetrain in a
lowracer, aero package.

However, I’m having an issue with the front end that I could
do with a bit of help with.

Photos of progress to date: 

The bike has been loosely built up and ridden for approx. 2hrs.
 The learning curve seems to be about the
same as for the Nocom – I could ride it pretty much straight away, although I’ve
got to concentrate and occasionally it’ll swerve to one side for no
apparent reason (as the Nocom did when I was learning)

The issue is that the front end is too wide – it uses a standard
135mm ‘rear’ hub which has a disc on one side, and a 9-speed cassette on the
other.  Cranks are 155mm.  Even with a 127mm width bottom bracket, and some 3mm pedal
spacers, my calf is rubbing on the disc mechanism, and my heel is rubbing on
the derailleur on the other side. The Q factor is already far too wide with
this set up, I don’t want to go further (although this would solve the
clearance issues) as it is affecting pedalling efficiency.

I think I need to go with a standard calliper front brake, and
somehow find a narrow ‘rear’ hub that will still take a 7,8,9 or 10 speed
cassette.  Any ideas?

I’ll bring it to Curborough tomorrow along with the Nocom...

Edited by russellbridge - 22 February 2016 at 11:06am

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russellbridge Members Profile Send Private Message Find Members Posts Add to Buddy List BHPC Member Joined: 21 October 2013 Location: Manchester Status: Offline Points: 843	Post Options Post Reply Quote russellbridge Report Post Thanks(0) Quote Reply Topic: MBB lowracer Posted: 26 September 2015 at 5:27pm
	MBB lowracer build. I’ll do a full write up of this for the magazine, but in short: I’ll set my stall out from the outset – I’m trying to build a moving bottom bracket (MBB) lowracer that I can add a rear fairing to, which will be fast enough to play with the ratracers next year in ‘part faired’. I think that the Nocom is not efficient in transferring pedalling input via the long chain & idlers to the rear wheel, hence my desire to experiment with a very efficient, short drivetrain in a lowracer, aero package. However, I’m having an issue with the front end that I could do with a bit of help with. Photos of progress to date: The bike has been loosely built up and ridden for approx. 2hrs. The learning curve seems to be about the same as for the Nocom – I could ride it pretty much straight away, although I’ve got to concentrate and occasionally it’ll swerve to one side for no apparent reason (as the Nocom did when I was learning) The issue is that the front end is too wide – it uses a standard 135mm ‘rear’ hub which has a disc on one side, and a 9-speed cassette on the other. Cranks are 155mm. Even with a 127mm width bottom bracket, and some 3mm pedal spacers, my calf is rubbing on the disc mechanism, and my heel is rubbing on the derailleur on the other side. The Q factor is already far too wide with this set up, I don’t want to go further (although this would solve the clearance issues) as it is affecting pedalling efficiency. I think I need to go with a standard calliper front brake, and somehow find a narrow ‘rear’ hub that will still take a 7,8,9 or 10 speed cassette. Any ideas? I’ll bring it to Curborough tomorrow along with the Nocom... Edited by russellbridge - 22 February 2016 at 11:06am

russellbridge Members Profile Send Private Message Find Members Posts Add to Buddy List BHPC Member Joined: 21 October 2013 Location: Manchester Status: Offline Points: 843	Post Options Post Reply Quote russellbridge Report Post Thanks(0) Quote Reply Posted: 08 November 2015 at 8:29pm
	I've got the front end sorted now using the following tricks: - I got rid of the disc brake and replaced it with a mini V-brake behind the front fork - I swapped the front 135mm hub (disc) for a standard 130mm hub and narrowed the forks - I swapped the standard rear mech for a Shimano Shadow rear mech which is narrower (thanks Geoff...) - I moved the rear mech hanger back 15mm All of these mean that I can pedal efficiently using a standard 107mm width BB. Now I've just got to sort the handlebars. The current set up (as above) works in a straight line, however on corners I've got a tendency to lean the inside knee out, which the current bar configuration stops me from doing. I'm going to have a play with a hamster set up, although I've not seem this done before on a MBB bike. Russ Edited by russellbridge - 08 November 2015 at 8:30pm

GeoffBird Members Profile Send Private Message Find Members Posts Add to Buddy List BHPC Member Joined: 20 September 2005 Status: Offline Points: 2396	Post Options Post Reply Quote GeoffBird Report Post Thanks(0) Quote Reply Posted: 08 November 2015 at 10:56pm
	Glad you've got the bike sorted and the dérailleur trick worked Russ.
	Right Time - Right Place - Wrong Speed

blogwat Members Profile Send Private Message Find Members Posts Add to Buddy List BHPC Member Joined: 30 January 2010 Location: nottingham Status: Offline Points: 661	Post Options Post Reply Quote blogwat Report Post Thanks(0) Quote Reply Posted: 09 November 2015 at 9:05am
	Hi Russ could you have a narrower handlbar and have them turned up or would that impair your vision too much, you could put your leg out then but it still my be tricky to steer I suppose. Jeff.
	when your up to your waist in aligators they forget to tell you you've got to clear the swamp

jdp298 Members Profile Send Private Message Find Members Posts Add to Buddy List Visitor (moderated) Joined: 24 February 2012 Status: Offline Points: 32	Post Options Post Reply Quote jdp298 Report Post Thanks(0) Quote Reply Posted: 18 January 2016 at 8:03pm
	Good looking sutff. Is there a view from the wise on the worth of MBB bikes (efficiency, hillclimbing aero etc)? Cruzbike don't seem to go lower than a midracer but the Vendetta looks like it goes well.

russellbridge Members Profile Send Private Message Find Members Posts Add to Buddy List BHPC Member Joined: 21 October 2013 Location: Manchester Status: Offline Points: 843	Post Options Post Reply Quote russellbridge Report Post Thanks(0) Quote Reply Posted: 19 January 2016 at 8:21pm
	Update on the MBB: I got the bike all built up including seat and rear fairing (alu frame and correx), then stripped it down, sprayed the frame, then built up it back up. Took it for a test ride last night around the local B&Q car-park and, apart from the alu-frame rattling like a knackered shopping trolley, it all worked fine. Rattles drive me mad so I need to fix these before I build it all up properly. Hard to gauge speed on a car park but it feels OK. I suspect it’s gonna be Hillingdon before I can test it back to back with the Nocom - I’m either gonna be very happy or very sad... Edited by russellbridge - 19 January 2016 at 8:23pm

AlanGoodman Members Profile Send Private Message Find Members Posts Add to Buddy List Admin Group Club Chairman Joined: 04 March 2005 Location: United Kingdom Status: Offline Points: 8036	Post Options Post Reply Quote AlanGoodman Report Post Thanks(0) Quote Reply Posted: 19 January 2016 at 8:50pm



Yanto Members Profile Send Private Message Find Members Posts Add to Buddy List Moderator Group Joined: 11 July 2005 Status: Offline Points: 1521	Post Options Post Reply Quote Yanto Report Post Thanks(0) Quote Reply Posted: 19 January 2016 at 10:42pm
	Looking good, maybe needs a bit of padding on the seat though It's hard to scale properly, but they look dinky wheels, 650c ? Are you going to extend the fairing down a bit so it shrouds the frame at the bottom then tapers up to the current bottom trailing edge of the fairing? Edited by Yanto - 19 January 2016 at 10:44pm

russellbridge Members Profile Send Private Message Find Members Posts Add to Buddy List BHPC Member Joined: 21 October 2013 Location: Manchester Status: Offline Points: 843	Post Options Post Reply Quote russellbridge Report Post Thanks(0) Quote Reply Posted: 19 January 2016 at 11:14pm
	All correct! 650c wheels - my legs aren't long enough to get around a 700 at the front - you can see how tight the bottom bracket is to the tyre. And yes, I still need to make the bottom bit of the fairing - I'm going to do this as one correx piece that's taped on (I think), so that I can get the rear wheel out (that's taken a surprising amount of thought to solve...) Russ Edited by russellbridge - 19 January 2016 at 11:24pm

russellbridge Members Profile Send Private Message Find Members Posts Add to Buddy List BHPC Member Joined: 21 October 2013 Location: Manchester Status: Offline Points: 843	Post Options Post Reply Quote russellbridge Report Post Thanks(0) Quote Reply Posted: 30 January 2016 at 9:34pm
	Has anyone ever tried using a gripshift with a gear cable as a method of actuating a brake? (a mini v-brake) I've just rigged it up and it seems to be OK, but can't test it at the mo (waiting for dry weather which might take a while...). Issues I can see: - it's a thinner cable so the tensile strength might be much less and snap - the cable outers are wound differently so if it there was a long length with lots of bends it may stretch differently (the actual length is short - about 300mm) - the cable barrel is smaller so it may rip through the plastic stop Anything else? Has anyone done it? Russ