[Closed] Potential bike bodge of the decade

Ambitious 😀 ! I guess if you hacked out the old bb from a frame with a wide enough downtube, you could possibly fashion that into a brace that would fit round the seattube....?

Instant death

Whatever I do will be overbuilt, so it won't snap and kill me. Most likely scenario is it'll work loose.

I guess if you hacked out the old bb from a frame with a wide enough downtube, you could possibly fashion that into a brace that would fit round the seattube….?

Hmm not a bad idea. My thought was to use thick sheet 6061 or 7075 and drill two BB shell sized holes in it, then fold the front of it to brace against the downtube. Then pack the void with a hard resin and drill and bolt through the gap between the downtube and seat tube. There are two challenges with this: drilling an accurate hole of the right size in the sheet; and finding the right alloy that can be bent in this way without losing strength or requiring complex annealing. I guess I could drill and bolt the whole thing maybe instead, and possibly bond it all in place too.

Sounds like a great idea.

Is there any way you could knock something up that screws into the existing BB shell with arms either side that would hold the new BB shell. then have a brace bracketed to the seat tube to stop it slipping downwards??

Probably wouldn't be strong enough, but I can see it in my head....

Do it for science

Needs more cutlery.

I can't think of a single reason not to do this. Definitely do it.

Can I have your Audi if you die? (the one with the gearbox bodge)

Alignment is definitely an issue, not insurmountable, but not easy.

Just do it all in carbon fibre. Use a tube with an ID of 46mm and a press fit bottom bracket.

Or just switch to a longer, say 140mm+ stem. 😉

To prevent any drilling to your frame could you attache a new BB shell using BB chain tensioners from the existing BB and some kind of clamp round the seat tube?

It would have to be braced against the downtube and seat tube to counter rotational forces.

With spoons, I hope.

Can I have your Audi if you die? (the one with the gearbox bodge)

It's a Passat and the gearbox was repaired and works fine I'll have you know!

Is there any way you could knock something up that screws into the existing BB shell with arms either side that would hold the new BB shell. then have a brace bracketed to the seat tube to stop it slipping downwards??

Thought about it but bonding to the outside of the existing BB tube would give a bit of extra strength

Just do it all in carbon fibre.

Considered it, but I have no experience with CF. I could take a cast of the existing BB cluster and make a form out of resin over which to lay the CF, This is actually not a bad idea and might be better than my original plan.

To prevent any drilling to your frame

I wouldn't drill the frame - just drill the brackets and bolt them to each other to hold it in place. The load would have to be spread across the existing tubes by packing the resin inside the voids.

Madness...
Live with it or sell it and buy a longer one.

How about two metal dogbones either side of each BB, that you screw in with BB cups (replacing the HT2 spacers)?

Bin Dun, in steel mind, and for diferent reasons.

[url= https://live.staticflickr.com/65535/50190954473_17d4cdd80b_o.jp g" target="_blank">https://live.staticflickr.com/65535/50190954473_17d4cdd80b_o.jp g"/> [/img][/url][url= https://flic.kr/p/2jtcL92 ]Untitled[/url] by [url= https://www.flickr.com/photos/92694523@N06/ ]tom.howard.562[/url], on Flickr

buy a longer one

You really think if I had the money for a new bike just sitting around doing nothing I'd be considering this? You do realise that some people cannot just buy whatever they want, right? That money is a finite thing?

Bin dun. In steel mind,

Would be much easier in steel.

Moar reach.... could you not fashion some rearward pedal extensions to achieve the same thing 🤔

Layback seat post?

This is by far your stupidest idea...You have to do it. I've nothing more constructive to add...

Layback seat post?

The cockpit is fine, even with a 35mm stem. The problem is the pedals are too far foward. So when standing, I am too close to the bars. I run a 50mm stem to help counter that but any longer and the steering gets a nasty flop.

Moar reach…. could you not fashion some rearward pedal extensions to achieve the same thing

Thought about it but you'd need a parallelogram arrangement with linkages and bearings. Possible if you had a CNC shop but not for me to do.

Could also fashion a new headtube that sticks out of the front of the bike but that'd be way more dangerous!

Clown shoes with SPDs at the toe end?

Bin Dun, in steel mind, and for diferent reasons

i met the original owner of that frame.. he was a sick bikes rider (chuckle) - -was built like that as apparently the tubing wasn't made long enough...

DrP

Now I'm thinking cut the BB off an old frame (possibly even steel) keeping part of the downtube which could be cut at an angle to fashion a gusset. Bolt and glue that around the existing downtube, then wrap the whole lot in carbon fibre. The angle of the gusset would allow the carbon wrap to be in tension which is what it'd need.

Clown shoes with SPDs at the toe end?

That requires riding with SPDs which this kind of bike does not suit. you're not wrong though - I had been riding more with my instep for control but I realised that pedalling more with my toes could add a good couple of cm to the effective reach, and it did too - I ride it up hills like that now.

Where's @bencooper when you need him.

He'd tell you it was a stupid idea and then he'd do it anyway.

There's most of a really good idea in there, geometry wise it all seems to make sense - lower, longer, etc. You'd end up with shorter chainstays, but you might like that.

I think what you might struggle with (if you did get it welded up) is the effect it could have on things like anti-squat - where the chainring ends up relative to the pivot might have the bike pedalling like a pig. I guess if the new shell is directly behind the old one, then it's in line with the pivot as per the original, but will still have an effect.

You mention the jig holding the frame by the BB - wondering if the ISCG tabs might help - if you cut out a BB shell plus tabs from an old/broken frame, you might be able to bolt it all together using the tabs and weld from there.

Admittedly I know nothing about nothing. But I'm wondering how the lowering and rearward shifting of the BB shell might affect Anti-Squat and the pedalling characteristics of the bike.

I haven't had a single pivot bike since my 2004 Marin Attack Trail. So I'm pretty certain things have progressed a LOT since then. But aren't they carefully designed to give the required characteristics?

True, if BB shell lowered then also your centre of gravity will be equally lowered so your 100% Anti-Squat intersection point (centre of gravity intersecting with front contact patch) moves proportionally down but I don't have a clue what that means in respect of the new chain lines in each individual gear.

Also the new pivot position would have an affect on the leverage rates on the shock?

My non-hambini brain is 'guessing' that as the BB is now further away from the pivot your weight on the cranks is inducing greater torque around the pivot which when the rear wheel tries to move up away from the ground over bumps, added to your extra torque means a higher leverage to the shock? Possibly needing you to jiggery pokery with your damping?

But awesome idea dude, love it! and especially the fact that you have the know-how to even conceive of the idea, make sure to wrap yourself up nice and safe when you test it and when you have it figured out come back and pleas help me figure out a way to hack-bodge my 2016 medium spectral to have more reach too, haha

EDIT: TLDR: what honorouablegeorge said, their post wasn't there when i started typing haha

If it doesn't involve table cutlery you won't even get past registration.

I hadn't considered anti-squat. The pivot is already pretty high, so perhaps it would be better to keep it the same height rather than lowering it. But then again, it was designed around a triple chainset where you were meant to climb in the little ring, and it would be going to 1x where it'd be doing its climbing effectively in the middle ring, which would also be larger than the current middle ring.

Also the new pivot position would have an affect on the leverage rates on the shock?

Hmm well when pedalling, maybe, but the shock can have plenty of compression damping dialled in, it's a Manitou SPV job. But not when descending really as everything else remains the same, the swingarm is in the same place as is the pivot.

If @bencooper had the facilities to weld alu I'd be on the blower...

There's also the option of welding a second headtube onto the existing one. Pedlaling unaffected, longer reach, slacker HA, tapered - you get it all.

True, and perhaps the frame mod people would do that. But isn't it a greater risk? Then again, it's an Orange so the whole thing is welded bits of alu.

That said - I'd have to slam the saddle forward to get a decent pedalling position if the BB stays where it is and it only just makes it ok, so I'd have no room for adjustment.

I'd imagine a new headtube could be made strong enough with gussets and the like, heat treatment permitting, and it might be an easier area to work in than around the chainset/BB

A slacker/longer bike is going to rotate the seat tube forward a little too, so it'll help seat angle.

(I'm really hoping you'll try this, I'm fascinated)

Just do it all in carbon fibre. Use a tube with an ID of 46mm and a press fit bottom bracket.

Or you could use something like this: BB30 to BSA Adapter

Fibreglass wrap all the (aluminium) surfaces you plan to bond to avoid galvanic corrosion, and then go nuts with teh Carbonz....

Or a reversible mod would be to fashion a pair of connecting plates, use some old BB cups to anchor the new shell to the existing shell...

I kind of see how extending the BB or headtube could work, in both cases can be a tube with flat plates welded on both sides. Rather than welding the frame and needing to dismantle/re-heat treat it you could put notches the BB/head tube have a tab on the bracket that fits in that so it doesn't rotate when mechanically fixed with a piece of threaded bar.

These are very highly stressed areas to be meddling with though, surely it'd be safer and easier to sell the existing bike/frame and a 2nd hand replacement that is correctly sized.

Headtube would definitely have to be welded though, which means going back to those fabricators I spoke to. They didn't seem to want the job though so I am a bit reluctant.

Moving the BB would result in an interesting bike I think. The thing is already very manoevrable because the wheels are small and hence chainstays are shorter than they would be on a 29er (I think) and my CoG is quite close to the rear wheel. Moving the BB could allow me to put my CoG even further back. So it will remain manoevrable but have a moderate reach (still won't really be long) and have masses of travel still.

Of course 40mm extra is about the minimum. I could move it more than that...!

surely it’d be safer and easier to sell the existing bike/frame and a 2nd hand replacement that is correctly sized.

Sure, if you can find me a frame that's 150mm+ travel, suits a 170mm fork, is non boost, 26" and has a reach of 460mm+ for £50 let me know 🙂

twisty

it’d be safer and easier to sell the existing bike/frame and a 2nd hand replacement that is correctly sized.

It would have been safer and easier if Hilary hadn't climbed Everest

It would have been safer and easier if Hilary hadn’t climbed Everest

Not for Tenzing

Does anyone have a broken alu frame you want to donate to the project? Will pay postage.

Back to the subject, how about using something like Scotch Weld 420?

£49.99 for a Banshee Spitfire BB from a frame which wasn't modified, but snapped anyway?

I think this is a brilliany horrid idea.
You'll end up with comically short rear center and presumably loop out everytime the trail points uphill.
I'm in the headtube extender camp with the new headtube slacker to steepen the ST with your saddle slammed forwards to bring the pedals more under your feet.

I would wrap it with kevlar, not carbon. Carbon is very stiff, but kevlar is better at tension. Sit your new BB shell where you want it and fix it with something like JB weld. Fill the gaps with epoxy and micro-balloon filler (or sawdust if the weight doesn't bother you). Then paint liquid epoxy on the surface and wind kevlar strand or narrow tape round it until you're bored, keeping it saturated with epoxy.

How strong it needs to be depends whether it has to cope with just pedalling and chain tension, or landing jumps.

Back to the subject, how about using something like Scotch Weld 420?

Having done a bit of stuff with glues and composites in the past, there is no way I'd trust adhesive alone to hold a high stress area in tension, epoxy and carbon fibre strapping perhaps - but getting decent compression for a strong glue-up seems fiddly.

Could you not bolt something through the original BB, (like This chap has, attaching your new BB shell to some plates somehow? May fall foul of £50 budget...

Having done a bit of stuff with glues and composites in the past, there is no way I’d trust adhesive alone to hold a high stress area in tension

Me neither. My design relies on 'glue' in shear with as high surface area as possible. Which I believe is the best way to use it no?

Could you not bolt something through the original BB, (like This chap has, attaching your new BB shell to some plates somehow?

On that bike the pedal pegs are below the centre of the BB so there's no rotational load. In mine, all the weight would be behind the old BB so it will experience all my weight in rotation. That is the biggest issue.

I would wrap it with kevlar

Good info thanks.

Here is the putative design - apologies for poor quality. The labelled CF wrap is just to show where the main stresses will be - the whole lot will be wrapped in many many layers, but it will be laid up bearing those directions in mind. The alu plate labelled will probably be 4 or 5mm 7075 as it does not need to be shaped or worked. The donor part is a bb and short section of seat tube that is 'mitred" to but against the existing seat tube and glued in place for good measure and to aid fabrication - I might use a steel one so I can split the tube and flay it to make two flanges that I can wrap around the existing seat tube and glue in. Not sure yet.

[img] [/img]

Could you not clamp something to the seat tube/ISCG mounts as well?

I don't have ISCG mounts this is a 2007 frame :). Also would never be strong enough.

On that bike the pedal pegs are below the centre of the BB so there’s no rotational load. In mine, all the weight would be behind the old BB so it will experience all my weight in rotation. That is the biggest issue.

Stick some elastomer between the seat tube and new BB then market it as the Fasst Flex Suspension <s>Handlebar</s> Bottom Bracket

With a donor frame you also have the option of using the chainstays to brace against the existing BB shell, with a bit of skillful dremeling of the donor stays and seat tube it'd butt neatly against the frame, if you get a CF donor then the whole addition can be composite, perhaps by cutting some slots in the existing BB shell you'd then have a nice way of lashing together with carbon tow or aramid yarn, although I'm still nervous about how to make it safe/strong enough the existing BB shell itself could bend.

I guess your'e also going to go 1x?

I guess your’e also going to go 1x?

Yes I have shifter mech and cassette already, will just get a chainring (that's larger than the 30T I have spare, which would be a little silly on a 26er).

I like the idea of using the chainstays to boost rigidity, however I am not sure a CF donor will work because it will be difficult to attach the new BB shell to anything and I'd be relying on just the CF weave which is less predictable for me at least.

I might try and grab a couple of cheapo skip bikes to hack apart to test this out for a trial run and to allow destructive testing.

I have a trickstuff eccentric bb that would move it a bit.

There is a frame builder on retrobike user danson67 who does alloy repairs etc and is very good.

I don’t have ISCG mounts this is a 2007 frame

TBF by 2007 ISCG had gone through 2 revisions...

Anyway your proposal looks like great fun to me (from the sidelines).
Of course you could try a "hybrid" solution, mitre/Squash and weld the donor seat tube stump to the back of the existing seat tube, while butting the two shells up agains one another and run a fillet along the under/backside where they meet, then fill out the voids with epoxy and wrap the lot in carbon...

Can you make it a a sort of I drive unit and suspend the bb from the original shell? It could be fabed in steel and then clamped to.a custom bb insert in the original shell.

No welding and reversible...

Put a longer stem on it and ride it.
It's an interesting theoretical project but it's not going to work because the BB is the central pivot point for the interaction between the rider and the bike and you can't bodge it well enough.

Could you not get someone to weld up a new front triangle in the length you want and then just attach the current swingarm? Some guy did it a few years ago with his old Lawhill bike as he wanted it with more modern geo. A friend did it with an old Alpine 160 as he wanted an XXL one for his 6’4 frame

If you are really determined to go ahead I would try a different bodge.

Make up a new head tube and some plates to attach it.

(Old frame + hacksaw may be the easiest way)

weld the new head tube assembly to the existing head tube giving a longer reach.

You can position the new head tube so that the bottom bracket moves down and back a little bit and the seat tube angle gets a little steeper and then also move the saddle fully forward on the rails.

The probability of you ending up with a wrecked frame, or injured when it goes wrong is fairly high and £50 is unrealistic unless you can weld aluminium yourself.

I think this will cost more than £50 and ride like a bag of shit. Obvs when standing your bodge would work but pedalling seated will feel weird as you'll be effectively pitched forward. It'll be a bastard to get it all aligned properly too. Good luck, happy to be proven wrong

Sorry but this is a ****ing awful idea. I can't see how you are going to support the new BB in such a way that it won't shear off as soon as you drop anything. Getting it welded properly would cost more than just sourcing a new frame. Patriots appear to sell from an absolute minimum of £100 on fleabay.

Sure, if you can find me a frame that’s 150mm+ travel, suits a 170mm fork, is non boost, 26″ and has a reach of 460mm+ for £50 let me know 🙂

A large 2004 Norco Shore like I have sizes up to 450mm reach by my calcs. You might get lucky and find a frame only for £150, 2005 Atomiks are the same frameset. Bikes like this exist.

http://web.archive.org/web/20040825000811/www.norco.com/bikes/2004bikes/vpsshore.htm

I realise not everyone has money to just piss away on bikes but you're proposing going through a lot of effort and actual expense to end up with something nobody would ever want and actually end up in a worse position than when you started.

It wasn't a spoon!

There’s also the option of welding a second headtube onto the existing one. Pedlaling unaffected, longer reach, slacker HA, tapered – you get it all.

Yea, this is what I would do. It's been done before too - anyone on the SDA scene a few years back would have seen Ian Mac's Diamondback Sabbath with an extra headtube welded on in front of the original.

The BB idea was interesting until I saw that you weren't planning on welding it. Yikes!

weld the new head tube assembly to the existing head tube

If I had the facilities to weld do you think I'd be farting about with carbon wrap? Welding alu is difficult and it needs heat treating afterwards.

2004 Norco Shore

That looks from the picture far worse than what I currently have. It looks very steep and about three miles off the floor.

I have a trickstuff eccentric bb that would move it a bit.

This was considered. EBB and reach extender headset would add about 12mm best case.

There is a frame builder on retrobike user danson67 who does alloy repairs etc and is very good.

I would prefer to get a framebuilder to do it properly, for sure.

Or make one crank 40mm shorter and the other 40mm longer, hey presto bike will feel 40mm longer.

Why does that make me think 'bollocks'? 🙂

Anyway, before you do anything irreversible to the frame (though I do look forward to the reversing it thread when you don't get on. This from me who in the days before droppers would stop two or three times at the start of a ride to get the saddle height right 'I've put it down too far...) just one suggestion:

Have you considered shortening your arms?

Until I saw your sketch I had a mental picture with the extra BB about half a diameter lower than the existing. I think (if it doesn't ruin the geometry) that would help in getting a vertical component of support from the wrapping.

i say go for it. Parts for the build are cheap enough

https://www.ebay.co.uk/itm/2-drawer-metal-filing-cabinet/264815015075?hash=item3da83474a3%3Ag%3AjdUAAOSwFcVfJIl0&LH_ItemCondition=3000

though I do look forward to the reversing it thread when you don’t get on.

Well, all this would be glued on. So at worst, I'd just have to remove the glue with acetone or something, or at worst sand it off.

Until I saw your sketch I had a mental picture with the extra BB about half a diameter lower than the existing.

Yeah I was thinking that lowering by 10mm would be good. BB height is about 310mm or something now I think. So that's a possibility.

Not sure I can face going through whole thread and pretty sure this idea will be in there. The most obvious is to make two plates with two BB holes, front gets bolted to current BB with usual BB outer ‘bolts’, just like you’d fit a spacer or chain device plate. The rear holes then take a BB tube threaded etc and that’s held in place with new rear BB and cranks etc.. Prob need to make sure this set up doesn’t turn in the plates, so just a screw in metal strap going up would sort that.

I’m in favour of the head tube option being a more ‘elegant’ solution. ‘Elegant’ obviously being a relative term in this context...

I’m also torn between recommending crowdfunding Molgrips inevitable rehabilitation fund or a more likely cheaper new frame...

It's unlikely to hurt that badly if it goes wrong - certainly less than a headtube! Likely worse case scenario with all that kevlar wrapping is that it'll come loose, not fall off instantly.

That looks from the picture far worse than what I currently have. It looks very steep and about three miles off the floor.

It was an illustration to point out the fact that such bikes exist. You can add bastard heavy to that list as well.

It’s unlikely to hurt that badly if it goes wrong

Only if you have no sensation from the waist down.

It’s unlikely to hurt that badly if it goes wrong

Yep. You're unlikely to even feel it if your BB snaps off when you land a drop.
Probably wouldn't even notice until you tried to pedal again.😁

It was an illustration to point out the fact that such bikes exist

It's not really an option if it's got worse geometry than my existing bike 🙂

This bike is reasonably rideable for XC as it is, and it weighs about 31lbs. I doubt that Norcco would be those things. It also has a HA of 67 degrees, would be a bit scary with a 170mm fork!

The Patriot is ok for pedalling with the shock in the middle position, sort of shaped like a trail bike but doesn't feel like one. If I move the shock mount, the HA is 'right' and you can charge through anything which is brilliant fun, but then the pedalling becomes a right chore. I can see why modern Enduro bikes are the way they are based on this.

It’s not really an option if it’s got worse geometry than my existing bike 🙂

This bike is reasonably rideable for XC as it is, and it weighs about 31lbs. I doubt that Norcco would be those things. It also has a HA of 67 degrees, would be a bit scary with a 170mm fork!

The Patriot is ok for pedalling with the shock in the middle position, sort of shaped like a trail bike but doesn’t feel like one. If I move the shock mount, the HA is ‘right’ and you can charge through anything which is brilliant fun, but then the pedalling becomes a right chore. I can see why modern Enduro bikes are the way they are based on this.

. < point you > .

I'm talking about the reach, stop obsessing over everything else. My point is that other frames exist with that sort of reach in the criteria you specified and rather than bodging your existing bike you could be doing some research and finding the right frame. As another example:

https://www.specialized.com/gb/en/pitch-pro/p/22892?&searchText=9301-1202

I built one of those up, got the frame for about £150 off the classifieds. By no means an XC whippet but pedals well enough uphill. No, it's not what you're after but itproves bikes with longer reach exist.

And FWIW the shore is actually fine with my 170mm Super T's as well which it should be as that's what it was specced with from new. Unless you want to go uphill. Don't go uphill.

 It also has a HA of 67 degrees, would be a bit scary with a 170mm fork!

Don't be so melodramatic.