# MTB cruiser starting to take shape



## MPU (May 15, 2009)

Here's a few pics of my latest frame. It's been five years since my last frame. This one is lugged mtb cruiser from Columbus Thron, Gara and Cromor tubing with 4130 top tube. Lugs are Long Shen and Everest.


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## MPU (May 15, 2009)

I have some troubles figuring out how to braze the seat lug. It's made of seat collar that's not a sleeve, the upper part is supposed to be reamed to 27.2mm after brazing. I want to make it to look like a lug. I'm planning to braze the seat stays on the sides of this lug. Should I braze this seat lug with brass and then braze the seat stays on it with silver? Can I braze the whole lug/top tube/seat tube together at once or should I first braze the lug together? How about brass brazing the lug/tt/st and fillet brazing the seat stays on the sides?








Marko


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## dbohemian (Mar 25, 2007)

Well, there are two potential ways that I would attack it. First you could just use bronze and tack/fillet joint, sweat top tube and seat tube all at approximately the same time. Then either use bronze or silver to do seat stays.

Or you could bronze fillet braze the TT lug to the ST sleeve, finish it all up nice and pretty then assemble frame as if it was a standard lug with silver braze. Silver braze seat stays. 

The second way is probably how I would do it but either would work.


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## todwil (Feb 1, 2007)

*Sweet!!*

Very nice frame are the ST going to be radius also? :thumbsup::thumbsup:


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## mchimonas (Dec 19, 2008)

*brass versus silver*

These are very good questions. Ideally, because this is a "mock lug" and the ST-TT is more of a "butt joint" than a "lap joint," the end of the TT should be brazed to the ST with brass using a fillet. However, the two parts of the mock lug going onto the ST and TT are more like "lap joints" and you will achieve better penetration with silver. A problem with brass brazing next to a joint already brazed with silver is that you risk drawing out the silver alloy and sort of messing up your previous work. One solution would be to braze the whole thing with brass, the problem with that is that it is tricky to get good penetration of the brass into a "lap joint." Another solution would be to use something like 45% silver alloy for the "lap joints" first, which, although more sluggish than 56% would still penetrate much better than brass. Next perhaps use something like fillet pro SS to do the "butt joint" which makes strong fillets and generally has a lower working tempertaure than 45% silver and wouldn't mess up the the joints under the sleeves too badly. Alternatively, if you are very good at temperature control, you might be able to do the whole thing with fillet pro SS. Ask David Bohm or the guys at Cycle Design group.


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## mchimonas (Dec 19, 2008)

*my apologies*

Sorry, I hadn't realized David Bohm had already replied (our replies were only 6 min apart so his was not visible to me yet). Disregard my previous message.


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## CBaron (May 7, 2004)

MPU,

Can you let us know what the radius of the bend in the TT is? It looks good.

Thanks
CJB


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## dr.welby (Jan 6, 2004)

How about a side view that jig? What's going on under the tubes?


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## Yogii (Jun 5, 2008)

Sweet looking! Please keep posting the progress.
I really like it..........


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## Customization (Jul 12, 2011)

nice work


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## MPU (May 15, 2009)

Thanks for advice and comments. Top tube is from j-ro. I don't know the radius it's bent. Seat stays will be curved too. The jig is just U- and L- shaped aluminium bolted together. 6mm bolts are under each tube for height adjusting and L-shaped pieces are under down tube, in front of head tube and behind seat tube to keep the dt/st and ht angles correct.
Marko


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## edoz (Jan 16, 2004)

That's a nice looking frame so far, keep up the good work and keep posting pics.


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## j-ro (Feb 21, 2009)

MPU said:


> Thanks for advice and comments. Top tube is from j-ro. I don't know the radius it's bent. Seat stays will be curved too. The jig is just U- and L- shaped aluminium bolted together. 6mm bolts are under each tube for height adjusting and L-shaped pieces are under down tube, in front of head tube and behind seat tube to keep the dt/st and ht angles correct.
> Marko


I don't know what the radius of that piece was either, I just rolled it untill it looked 'right'

If I had the straight across length of the bottom and the height that it rises in the middle I could figure it.

If memory serves, it would be close to this;

If the tube was 21" across the two lower points and the underneath rose 1.25 inches above that line the radius would be around 44"-45"


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## MPU (May 15, 2009)

The frame is pretty much brazed and filed. Some cable mounts still to braze and some sanding too. Now I'm waiting for Pacenti MTB fork crown and fork blades/steerer tube. First I thought about using an unicrown rigid fork but I think this frame needs a lugged fork. 
For seat lug I forgot the top tube "lug" and fillet brazed the top tube to the seat lug. Seat stays are mitered and silver brazed to both top tube and seat tube. 50mm wide tire fits just fine to this frame. I'm going to use Schwalbe Big Apple 2" tires as most of the riding is more like commuting than real MTB. For MTB riding 2" wide Hutchinson Pythons fit fine and they are big enough for me.



















Marko


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## Clockwork Bikes (Jun 17, 2006)

Very nice and great job on the lugs.


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## 18bikes (Jan 15, 2007)

Nice! I really like the lines, it just looks right. Only change I'd make is a curved chainstay/seatstay brace but that's a minor niggle

Matt


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## Yogii (Jun 5, 2008)

Wow is that sexy....Please do a very nice two tone paint job.


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## MPU (May 15, 2009)

18bikes said:


> Nice! I really like the lines, it just looks right. Only change I'd make is a curved chainstay/seatstay brace but that's a minor niggle
> 
> Matt


That brace is curved a bit. It just doesn't show well in this angle.
Marko


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## MPU (May 15, 2009)

Yogii said:


> Wow is that sexy....Please do a very nice two tone paint job.


Two tone for sure. I'm thinking about very light beige and brown as I have brown leather saddle and Brooks leather grips. Or maybe black and vanilla.
Marko


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## loose chain (Apr 13, 2011)

far out. i literally finished an almost identical design (down to the seat stay junction-though i was thinking going a little more bullet style) in CAD yesterday. i swear, today is the first time i've looked at this thread. building it for a friend who's 6'5" and wants something to ride around town and "jump curbs and stuff" with. what "looked right" for me in CAD was a radius of 985', from headtube to rear axle. now, just hafta see if i can pull it off (will be bike #3 for me).

anyways, nice work. now i have something to aim for...


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## Yogii (Jun 5, 2008)

Please weight that sexy thing......thanks


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## benwitt11 (May 1, 2005)

That's gorgeous. I am such a sucker for cruiser Mtb's. My current imaginary lust object is a cruiser SS fat bike for summer use. This bike pretty much hit it on the head of what I'd want. Well done.


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## MvonStein (Oct 4, 2009)

Nice! I like the way you joined and capped the seatstays.


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## MPU (May 15, 2009)

Brazing is pretty much done. I'm still not sure if I make struts for the fork or not. I may braze some mounts for struts and see what the bike looks like with/without them. Next sanding the whole frame and painting.
Marko


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## RCP FAB (Jun 15, 2011)

Fork looks real good as is.

So does the frame. Good work.


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## marks_bike (Aug 22, 2006)

Nice job!

Who makes that disc brake tab?


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## MPU (May 15, 2009)

marks_bike said:


> Who makes that disc brake tab?


Me myself out of 4mm steel plate. Hacksaw, drill press and files are my best friends
Marko


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## todwil (Feb 1, 2007)

Nice build cant wait to see it painted and dirty


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## MPU (May 15, 2009)

Done! Test drive tomorrow, so far I've tried it on the alley and everything works and feels nice.


















Marko


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## BILL E (Apr 13, 2011)

Hey Marko, she looks beautiful, you should be rightfully proud of your creation.


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## benwitt11 (May 1, 2005)

That looks really classy. Nice job picking the colors, it works very nicely indeed.


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## jgerhardt (Aug 31, 2009)

I am curious how that fork holds up with that disc tab. What fork blades did you end up using?


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## todwil (Feb 1, 2007)

Bike turned out perfect!


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## mickuk (Jul 6, 2007)

Finally got to see the pics (work firewall wouldn't let me)! Nice work - lots of good choices (shape, colour, finishing details)

Will it be another 5 years until the next one?


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## MPU (May 15, 2009)

jgerhardt said:


> I am curious how that fork holds up with that disc tab. What fork blades did you end up using?


I used Pacenti fork blades. I suppose I'm such a wussy rider that they will hold up just fine. If not then it's time for thicker blades.
Marko


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## j-ro (Feb 21, 2009)

Bike looks great Marko! thanks for keeping us posted with pictures.

I've got a real soft spot for anything with Mary's bars on it, this one looks just right.


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## Yogii (Jun 5, 2008)

Is that cream and gold?


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## JerryW (Nov 18, 2008)

Great looking frame. I really like how the top tube curve flows into the seat stays.


Jerry


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## MPU (May 15, 2009)

Yogii said:


> Is that cream and gold?


Pretty much yes.
Marko


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