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Author Topic: CB250 RS - Project "Phoenix"  (Read 5122 times)

Offline teazer

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Re: CB250 RS - Project "Phoenix"
« Reply #10 on: Feb 19, 2018, 20:39:13 »
Just out of idle curiosity, how do you plan to get around an MOT and Construction and Use regulations?  I thought the UK required rear bodywork to extend to the rear of the rear tire.

Offline paddyshepherd

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Re: CB250 RS - Project "Phoenix"
« Reply #11 on: Feb 20, 2018, 03:58:52 »
Just out of idle curiosity, how do you plan to get around an MOT and Construction and Use regulations?  I thought the UK required rear bodywork to extend to the rear of the rear tire.

You're correct in the C&U Regs aspect, but it's not an MOT issue as well.
However, the C&U gets greyer and greyer the older the vehicle is. The official wording is "as far as reasonably practicable" a mudguard must catch any spray from the rear tyre. A guideline is 2/3rds to 3/4 of the tyre should be covered - by the time I get a number plate attached to the back, it won't be far from this region. I can't see any issues arising from it in my area.

Edit: as a bit more background info, I'm loosely using this article as a guide for my build, since a lot of the bikes I'm taking inspiration from follow most of this theory: http://www.bikeexif.com/build-cafe-racer

So the reason for the small hump is to do with the Visual Weight. I am however, planning on shaping the side profile of the hump to match the squared tank, so the back end of the bike might be slightly more squared off to match the steep sides of the tank.
« Last Edit: Feb 20, 2018, 09:02:11 by paddyshepherd »

Offline teazer

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Re: CB250 RS - Project "Phoenix"
« Reply #12 on: Feb 22, 2018, 23:45:02 »
Sorry to be the bearer of bad news but that article was a bunch of BS with nonsensical ideas such as "bone lines' which mean absolutely nothing on a bike.

Go with what looks right or balanced to you and if that's big butt or tiny arse, that's all fine.  It's what looks right to you and obviously has to be ergonomically sound and safe.  Some of us lie sixties Tritons with slightly larger seats.  Some prefer MotoGP or Ducati WSB rear ends. The seat hump just has to look like the correct proportions to you.

Many people use a second tank from the same model bike to get a matching back end, but not all tank shapes lend themselves to that approach. I use a combo of CAD (cardboard aided design) and analog photoshop - a print and pencil/crayons and a pack of plain white labels and a large eraser a.k.a. the "delete" function.   

Offline paddyshepherd

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Re: CB250 RS - Project "Phoenix"
« Reply #13 on: Feb 23, 2018, 04:42:09 »
Sorry to be the bearer of bad news but that article was a bunch of BS with nonsensical ideas such as "bone lines' which mean absolutely nothing on a bike.

Go with what looks right or balanced to you and if that's big butt or tiny arse, that's all fine.  It's what looks right to you and obviously has to be ergonomically sound and safe.  Some of us lie sixties Tritons with slightly larger seats.  Some prefer MotoGP or Ducati WSB rear ends. The seat hump just has to look like the correct proportions to you.

Many people use a second tank from the same model bike to get a matching back end, but not all tank shapes lend themselves to that approach. I use a combo of CAD (cardboard aided design) and analog photoshop - a print and pencil/crayons and a pack of plain white labels and a large eraser a.k.a. the "delete" function.

Oh don't get me wrong I'm not following it word for word, (hence loosely!  ;D) but I've noticed that a lot of the bikes I have used as inspiration do follow those theories to some extent. I think the reason I like a smaller back end is because I also like the Brat bikes with no hump at all.

Having said all that, I've had a complete rethink on the back end yesterday and had a bit of an idea. It sounds a bit bonkers at first but I plan on using a natural wood skateboard deck, (varnished and polished and trimmed to match the frame width), to form the seat base, hump mount, and back of the bike. I've seen it done on a couple of bikes and for my build it makes sense (being a longboarder and snowboarder, it adds a bit of personal quirk to it too). It's easier to explain with a sketch. It's easy to work with, cheap to fuck up, easy to mount stuff to and fairly lightweight too.

You're welcome to call it out as a stupid idea, but I reckon with the right varnish and finishing touches, it could look pretty cool.




Offline cb250nproject

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Re: CB250 RS - Project "Phoenix"
« Reply #14 on: Feb 23, 2018, 07:03:52 »
mate the bike looks really good, I'm running a similar seat also. beauty is in the eye of the beholder mate,if you have a clear idea of what you want she will come out fine.

I'm hanging to see this build progress
first cafe build was an incomplete learning experience, more of a test run for the real thing FRANKENHONDA II

Offline paddyshepherd

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Re: CB250 RS - Project "Phoenix"
« Reply #15 on: Feb 23, 2018, 10:00:47 »
mate the bike looks really good, I'm running a similar seat also. beauty is in the eye of the beholder mate,if you have a clear idea of what you want she will come out fine.

I'm hanging to see this build progress

Thanks mate - I've had a look through yours too.

Hopefully we'll be back on with some progression in a week or so, off to France in the meantime. I can't really do much now until I get the frame cut and welded (need the top of the triangle making a bit more horizontal!) before I can start looking at tank mounting and seat unit.

After that I'll move to the front end and the engine.

Offline paddyshepherd

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Re: CB250 RS - Project "Phoenix"
« Reply #16 on: Mar 07, 2018, 06:29:32 »
Back from France now so started making a little bit of progress and mocking up.

I've removed the rear mudguard mount so that I could drop the skateboard deck into place and review the lines of where I want it to finish the back end off etc.



Roughly where I expect it to sit, just behind the shock mounts with the frame tapering up to it using a triangular piece of plate. That piece of plate will also form the rear seat base (i.e. skateboard deck) mount.


This pic shows where I expect the back end to finish frame wise, and I'll be having the top bar of the rear triangle raised up and shaped so it comes in level with the back of the shock mount where the spirit level is sat. Sent these over to my welder so he knows what to expect when I bring the bike to him.



Offline teazer

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Re: CB250 RS - Project "Phoenix"
« Reply #17 on: Mar 07, 2018, 23:48:38 »
It all comes down to personal taste and it's your bike.  To me "Brat" style is going back to a basic standard bike and they don't get me excited, but that's just me.  Lots of people like that look.  I do like your sketch of what you are trying to do.

Do you have a decent welder close to you? It would be possible to modify the frame to make it a flat top leaving the rear shock mounts in place but changing the tubing in front of the mounts. 

Offline datadavid

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Re: CB250 RS - Project "Phoenix"
« Reply #18 on: Mar 08, 2018, 04:31:11 »
Oh no not a skateboard seat!

Offline paddyshepherd

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Re: CB250 RS - Project "Phoenix"
« Reply #19 on: Mar 08, 2018, 06:31:34 »
It all comes down to personal taste and it's your bike.  To me "Brat" style is going back to a basic standard bike and they don't get me excited, but that's just me.  Lots of people like that look.  I do like your sketch of what you are trying to do.

Do you have a decent welder close to you? It would be possible to modify the frame to make it a flat top leaving the rear shock mounts in place but changing the tubing in front of the mounts.

Yeah, I know what you're saying there - I do like brat bikes but it takes a lot for one to really stand out. This won't be a brat, but it will have a couple of small cues from brat bikes (like the seat base), but it will definitely still have a small rear hump and a more café style colour scheme, probably with quite a lot of polished/brushed parts too. I'm kinda seeing it as a combination of styles. Hopefully it'll work out nice in the end. I'm focussing a lot on aesthetics so I'll be making sure it doesn't just end up looking a dogs dinner of parts. It may sound that way at the moment but I've got a clear image in my head of how it will all flow together - it's just difficult to visualise and show when there's only half of it there!

As for the frame, what you've described is exactly what I'm planning on having done. The new top bar will join at the top of the shock mount such that it's perfectly level. I'm lucky in the fact I've got two good friends who are both very good welders. I've said I don't mind how they do it as long as the end result is the same, but I envisage they'll cut the top bar out completely and weld a new one in, which will taper at the rear end to merge with the top of the shock mount.

Oh no not a skateboard seat!

Not sure how that input is helpful in any way, shape or form.