Hi my name is John ,
I am building a fat 1981 mongoose based on the motomag frame and forks, called a fatgoose 170, It has taken a year to get to this stage but have hit a bit of a problem and would welcome some advise please.
It is fitted with the rear wheels taken from a schwinn stingray chopper and I have widened the crank by 60mm total, the frame geometry is the same but the bike is wider.
I am trying to make it look as much as a 1981 mongoose as possible by using era parts and decals of 1981 accept the wheels and hope disc brake of course.
I built the bike complete in an unpainted state and luckily I did because when applying pressure on a power stroke as if you were in a starting gate the bb seems to have a little more flex than i'd like even though my supergoose also has flex when you do this.
I know a lot of frames have flex in a steel frame but with the added leverage on the crank it feels a bit much but I have not widened the rectangle section behind the bb.
I you could take a look please, I am open to suggestions, I have spoken to a frame builder and the standard size of tubing used is a big factor in the problem but I can't change it now, maybe if I brace it but not too much to move the problem to another area ?
I was thinking of widening the rectangle by 20mm either side of the it and then also welding a mongoose gusset between the down tube and the seat mast tube that was used on the 1975/76 mongoose frame.
from 77 onwards mongoose stopped using this brace and I don't know why, it would be interesting to know the answer.
Thank you for reading
John.
I am building a fat 1981 mongoose based on the motomag frame and forks, called a fatgoose 170, It has taken a year to get to this stage but have hit a bit of a problem and would welcome some advise please.
It is fitted with the rear wheels taken from a schwinn stingray chopper and I have widened the crank by 60mm total, the frame geometry is the same but the bike is wider.
I am trying to make it look as much as a 1981 mongoose as possible by using era parts and decals of 1981 accept the wheels and hope disc brake of course.
I built the bike complete in an unpainted state and luckily I did because when applying pressure on a power stroke as if you were in a starting gate the bb seems to have a little more flex than i'd like even though my supergoose also has flex when you do this.
I know a lot of frames have flex in a steel frame but with the added leverage on the crank it feels a bit much but I have not widened the rectangle section behind the bb.
I you could take a look please, I am open to suggestions, I have spoken to a frame builder and the standard size of tubing used is a big factor in the problem but I can't change it now, maybe if I brace it but not too much to move the problem to another area ?
I was thinking of widening the rectangle by 20mm either side of the it and then also welding a mongoose gusset between the down tube and the seat mast tube that was used on the 1975/76 mongoose frame.
from 77 onwards mongoose stopped using this brace and I don't know why, it would be interesting to know the answer.
Thank you for reading
John.
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