Rebuilding a broken Straight 8

Rat Rod Bikes Bicycle Forum

Help Support Rat Rod Bikes Bicycle Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Joined
Oct 2, 2012
Messages
884
Reaction score
3,886
Location
Brisbane, Qld.
Rating - 0%
0   0   0
Ouch.
Broke the seat tube off the Aluminium frame on my custom Straight 8. It was obviously tired - broke with hardly any weight on it. Seat post lower than minimum.
11 years old.
Is it done for - or weldable/repairable?

broken.jpg
 
Weldable by someone who has experience welding aluminum. it's not nearly as easy as welding steel. It's hard to get decent penetration with aluminum so it's unlikely the new weld will intrude into the seat post space. If it does, it's easy enough to file out with a rat tail file. It is important to get it straight so putting the seat post in before welding can help keep it aligned. A tack weld on each side can help it stay straight. Trying to weld all round in 1 pass will surely pull it crooked and you won't be able to get the post in. Many aluminum frames have big lumpy welds anyhow so it won't matter if it's a bit ugly. Some black spray paint will cover it okay. You can buy longer seat posts, up to 350 mm so you can get better support so it doesn't break right off again.

The minimum marks on seat posts aren't meant for any bike in particular. For that frame design the post needs to be a minimum of 2 inches below the weld. My local coop has received several bikes broken just like this. Most were Genesis brand, aluminum frames. Most had the seat post not in as far as the weld or thereabouts.Mostly a problem for aluminum frames with a lot of extra seat tube above the weld.
 
Thanks for that - I'll try and find a welder.
Will also keep an eye out for a rough Straight 8 for sale - it would be worth it for all the parts I have fitted - forks - Boxkars shifter etc etc
 
sometimes small friendly auto repair garages are willing to do small weld jobs like that.
 
Cheers - but I just bought a newer model in run-down-left-ouside poor condition, but the frame is structurally good - although will need painting.
Otherwise - straight component swap.
 
Pictures make it look in better shape than it is.

Now the question is what colour - I'm thinking I'll murder it - but ... flat white might be funky too.
new8.jpg
 
Now the question is what colour - I'm thinking I'll murder it - but ... flat white might be funky too.
Maybe something similar, still old school hotrod... My kid's Electra is done in a primer style red/brown, and it's a nice standout from all the flat black out there
910651274a49a4901a741819d3ed.jpeg
images (1).jpeg
 
Maybe something similar, still old school hotrod... My kid's Electra is done in a primer style red/brown, and it's a nice standout from all the flat black out there
Nice, I would - and I tried some blue that I had left over from the Peugeot - but after stripping it down and cleaning it up, I think I’ll take the easy option and go black.
After sanding, It looks like I can touch it up with some rattle can black and finish it off with some satin clear acrylic. That way I can reuse the existing fender and chain guard. Because stickers.
 
Wow, what a crack from the seat tube!
Normally when you repair an aluminium weld you'll have to heat treat it, or else the welded spot will be weaker than before.
Personally I would consider milling a new piece and rivetting it onto the frame, but that can be quite a undertaking.
 
Wow, what a crack from the seat tube!
Normally when you repair an aluminium weld you'll have to heat treat it, or else the welded spot will be weaker than before.
Personally I would consider milling a new piece and rivetting it onto the frame, but that can be quite a undertaking.
He found himself a new frame.
 
If it's any Dutch consolation, the broken frame is still in my garage, but the Straight 8 has been reborn - and I couldn't be happier.

As some of you may recall, this bike had big apes and a 'nanna seat previously, but as it's the only bike in my fleet with a coaster brake, I wanted to repurpose it for riding with my Whippets - but the big bars were a little cumbersome and ungainly for fast dog duty.

str8 copy 4.jpg


When are we going???

whippies.jpg


in the process of converting it, the frame let go first time I partially sat on it after I went back to a conventional seat/post. My guess is the welds were fatigued from dealing with when I was obese.

But now, with the replaced frame it's suitable rat rodded - and fit for purpose. Same for Davey-boy.

I also couldn't believe my luck when the Brooks Flyer saddle turned up on my Amazon feed for 50+% off. I used the bars off my Giant Fastroad, some other bits I had in stock, like the grips, stem and suspension seat post - and it's come up really, really well.

Turned out all it needed to match the parts I was transplanting was a couple of coats of rattle can matte on the new gloss frame. Job done.

Better pics to follow.

n81.jpg


n84.jpg


n83.jpg
 
If it's any Dutch consolation, the broken frame is still in my garage, but the Straight 8 has been reborn - and I couldn't be happier.

As some of you may recall, this bike had big apes and a 'nanna seat previously, but as it's the only bike in my fleet with a coaster brake, I wanted to repurpose it for riding with my Whippets - but the big bars were a little cumbersome and ungainly for fast dog duty.

View attachment 260803

When are we going???

View attachment 260802

in the process of converting it, the frame let go first time I partially sat on it after I went back to a conventional seat/post. My guess is the welds were fatigued from dealing with when I was obese.

But now, with the replaced frame it's suitable rat rodded - and fit for purpose. Same for Davey-boy.

I also couldn't believe my luck when the Brooks Flyer saddle turned up on my Amazon feed for 50+% off. I used the bars off my Giant Fastroad, some other bits I had in stock, like the grips, stem and suspension seat post - and it's come up really, really well.

Turned out all it needed to match the parts I was transplanting was a couple of coats of rattle can matte on the new gloss frame. Job done.

Better pics to follow.

View attachment 260804

View attachment 260805

View attachment 260806
This bike is fantasticly awesome.
 
With the amount of riding and whippet running down near the boat harbour your old frame might be worth holding onto. I know there are a couple of ally ‘tinny’ style boat builders around. They would have the gear and if they heat treat the hulls chucking a bike frame in as well would be ‘carton of beer’ territory.
 
Back
Top