OG fatgoose 170 update

[griff]

Will we be seeing this beast at MK?

I want to see you wheelying around Willen Lake 

[meticulous]

looks awesome!!!    get steve firebird to make you some fat oversized padset...

[Chapperz]

Love these unique builds and things like making your own stems etc.
Would love to see this too at MK.
Looks great cant wait to see it finished

[brakedancer]

http://www.mongoosemassif.com/specs/   

[snoopy72]

Thanks for the link, Interesting read, I have seen these, good value too
I was going to fit a sturmey archer 8 speed hub at one point but want to save the weight and you can't beat the sound of a white industries freewheel.
The mongoose massive is like a small mountainbike and not sure if you could use it for anything.

[snoopy72]

Will we be seeing this beast at MK?

I want to see you wheelying around Willen Lake 

Not sure I can make it to MK , as for Willen lake , my back's still playing up, having a job putting me socks on in the morning let alone wheelying.
When finished I do plan on getting some proper pics with a friends camera

[snoopy72]

Hit a bit of a problem 

[Jaymz]

I'd stick a couple of triangular gussets with holes through them on either side of the bb to mimic the goose gusset

[snoopy72]

That's what i'm thinking Jay, would like to mimick the 76 gusset, asking a couple of peeps dimensions of this gusset, not many 75/76 gooses around
Would like to just gusset along both sides of the rear triangle but might have to do between down tube and bb as well, where do I stop though ? could also do between seat post tube and bb both sides ,  what flex is acceptable ? before you could have frame failure

[Jaymz]

Crude I know, but something like this

[Wadz]

could you fit and internal sleve in the bottom bracket ,leaving it short effort to just fit the bearing cups as normal might streathen things up with out losing the looks.

[snoopy72]

It's also knowing where it will make a difference without bracing it everywhere, I could brace it like Jay suggested but maybe I would get the same effect along side the rectangle to the bb ?

[snoopy72]

could you fit and internal sleve in the bottom bracket ,leaving it short effort to just fit the bearing cups as normal might streathen things up with out losing the looks.

Can't do that because I still need to have the arms the same difference apart and it's the extra leverage that's causing the problem.
To be fair, might be better off leaving it , my standard mongoose frame flexes nearly as bad, i think all steel bicycle frames have a bit of flex there from what I have read.

[snoopy72]

Just had a thought,  if I do a gusset like Jay suggested matching the 75/76 goose on the drive side , which will eliminate up and down movement and on the left hand side another matching gusset but along side the rectangle to brace left and right movement.
It will help with stiffening it up but save all the weight of making match pairs of brackets

Two offset gussets with matching drill holes of a 76

[Gnarlyscoots]

To be honest, you will find those alloy cranks flex a lot too.

[snoopy72]

To be honest, you will find those alloy cranks flex a lot too.

Yes Terry, they are also flexing

[snoopy72]

I have contacted a couple of well known frame builders to get an opinion, see what they say, If  I brace the area in question it could also transport the problem to the top tube where it joins the seat post mast, I had a mitygoose that snapped here years ago.

[oldtired]

   love this project ,


could you not just fatten up the chain stay box?  making it wider, could be added to  rather than removing the existing one,  don't think it would spoil the looks as the rear end is so wide already , weld on the top join could be ground in so it looks like one box section , would have thought i would be stiff enough to stop the displacement transfer to the top/seat tube weld?

 looks to be about 80% of the bb width is covered by the chain stay box on a goose so perhaps it needs to be similar proportion on this , the gussets are a good idea but i think would detract from the distinctive goose chain stay bridge ?     

 this  may cause issues with the bottom tube  , twisting under load  at the bb? 

[snoopy72]

Thanks for all your thoughts and ideas, yes the flex feels to be at the rectangle tube , maybe if I enlarge the rectangle not to the full 80% as not to put the stresses towards the seat mast and down tubes.
What about enlarging the stay bridge and then fitting a 76 gusset between the down tube and seat mast to affectively join them together?
It would be interesting to know why mongoose fitted this gusset to the 75 and 76 and then removed it ?

[snoopy72]

  love this project ,

I'm not feeling the love at the moment 

[oldschoolace]

I think without having scaled up tube diameters to suit, your build was always going to be prone to a bit of flex. The width of the bb presents a considerable increase in leverage perpendicular to the seat tube. If you can live with it I would put up with the flex unless you have serious concerns about an actual failure of the frame. For me any gussets added around the bb short of a wider square section between the bb and the hoop would spoil the look of the build.

[snoopy72]

I spoke to a frame builder and he said if you brace it, it's a bit like sticking a band aid over it, it will only cause a problem at the end of each brace making that part the weakest, he also said the same as oldschoolace that ideally all the frame tubes needed to be enlarged, the only problem with this is you would then have a weak spot at the headstock because you would still have to use a normal size headset and stem.
I think you could go on forever and it certainly wouldn't resemble a mongoose when finished, I'm waiting for more suggestions apart from throwing it in the plastic thing with a lift up lid
Maybe just extending the rear rectangle a bit would help, this is where it feels weakest and then hope for the best, I certainly know it's not going to be suitable for a table top, I do like hutch bars but don't fancy a face full of them.

[oldschoolace]

This might be a total nonsense but would be easy to test. what about filling the tubes with, expanding foam? wouldn't add any weight but the honeycomb structure may help stiffen things up. You could cut yourself two identical pieces of copper pipe, fill one with foam and test it against the other with some weights hung over the middle.
As I say, could be bullshit but could also be a cheap and easy fix 

[snoopy72]

  I'm open to any suggestions at the moment, i'd fill the tubes full of tampons if it worked 
unfornunately the only tubes accessible are the rear stays and seat mast, the rest are sealed.
The flex doesn't seem to be getting as far as the rear stays only the bb area.

I suppose It will never be as flexible as riding a hinged Raleigh Hercules shopper bike with the hinge unclamped

[rodriguez]

I think it'll crack where the bb meets the box the way it is under heavy load, in my opinion that's the area pedaling will stress most as power is transferred to the rear wheel via the cranks.

I'd consider increasing the size of the box.

As it would reduce the bb flexing I think this might actually reduce the stress on where the down tube and seat tube meet the bb.

Might increase the stress where the down tube meets the head tube though.

Any structural engineers on here?