Spread aluminium frame to 150mm?

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cwah   10 GW

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Spread aluminium frame to 150mm?

Post by cwah » Jun 12 2018 10:32am

Hello

I'm considering getting a motor from QS that would be powerful enough to do 60km/h on 200kg load for start and stop traffic environment.

It also has a casted wheel like this one:
http://www.cnqsmotor.com/en/article_rea ... r/487.html

So no more fiddling with spokes, wheels out of shape and broken spokes.

However my frame is aluminium and 135mm dropout .

What are the risk to expand them by 15mm?

Thanks
Help me find my stolen electric brompton: http://bit.ly/1a0vbBC and Bosch Sinus B3 http://bit.ly/1eV0WQz

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MadRhino   100 GW

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Re: Spread aluminium frame to 150mm?

Post by MadRhino » Jun 12 2018 1:03pm

Alu frames are not all the same. Some can be spread pretty easy and safe, some won’t let you because they are too stiff and will spring back to original shape. If you have one of those, don’t insist for it will crack in the welded joints sooner or later if you force it to hold a 150mm hub.
Make it fool-proof, and I will make a better fool.
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cwah   10 GW

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Re: Spread aluminium frame to 150mm?

Post by cwah » Jun 12 2018 1:50pm

MadRhino wrote:
Jun 12 2018 1:03pm
Alu frames are not all the same. Some can be spread pretty easy and safe, some won’t let you because they are too stiff and will spring back to original shape. If you have one of those, don’t insist for it will crack in the welded joints sooner or later if you force it to hold a 150mm hub.
Thanks. How can I find that out?
Help me find my stolen electric brompton: http://bit.ly/1a0vbBC and Bosch Sinus B3 http://bit.ly/1eV0WQz

Springforward   100 µW

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Re: Spread aluminium frame to 150mm?

Post by Springforward » Jun 12 2018 3:02pm

How do you intend to stop this 200 kg projectile at 60kph ? Should be fun on wet London roads on a botched up frame and bike tyres.

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MadRhino   100 GW

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Re: Spread aluminium frame to 150mm?

Post by MadRhino » Jun 12 2018 3:32pm

cwah wrote:
Jun 12 2018 1:50pm
MadRhino wrote:
Jun 12 2018 1:03pm
Alu frames are not all the same. Some can be spread pretty easy and safe, some won’t let you because they are too stiff and will spring back to original shape. If you have one of those, don’t insist for it will crack in the welded joints sooner or later if you force it to hold a 150mm hub.
Thanks. How can I find that out?

You will know when you spread the dropout width. Either they stay spread or they spring back. :wink:
Make it fool-proof, and I will make a better fool.
Current bikes
Street: https://s20.postimg.org/ewrvugywt/Session_04_2015.jpg
Dirt: https://s20.postimg.org/lbqwr55ml/IMG_0157.jpg

cwah   10 GW

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Re: Spread aluminium frame to 150mm?

Post by cwah » Jun 12 2018 6:24pm

MadRhino wrote:
Jun 12 2018 3:32pm
cwah wrote:
Jun 12 2018 1:50pm
MadRhino wrote:
Jun 12 2018 1:03pm
Alu frames are not all the same. Some can be spread pretty easy and safe, some won’t let you because they are too stiff and will spring back to original shape. If you have one of those, don’t insist for it will crack in the welded joints sooner or later if you force it to hold a 150mm hub.
Thanks. How can I find that out?

You will know when you spread the dropout width. Either they stay spread or they spring back. :wink:
Hmm.. thx for your advice. I may stick to 135mm. Or go dual drive
Help me find my stolen electric brompton: http://bit.ly/1a0vbBC and Bosch Sinus B3 http://bit.ly/1eV0WQz

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MadRhino   100 GW

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Re: Spread aluminium frame to 150mm?

Post by MadRhino » Jun 12 2018 7:46pm

Or build the width with custom dropouts. That, is the proper way to do it.
Make it fool-proof, and I will make a better fool.
Current bikes
Street: https://s20.postimg.org/ewrvugywt/Session_04_2015.jpg
Dirt: https://s20.postimg.org/lbqwr55ml/IMG_0157.jpg

cwah   10 GW

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Re: Spread aluminium frame to 150mm?

Post by cwah » Jun 16 2018 2:49pm

How to do that on an aluminium frame? I can't do welding
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eCue   10 kW

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Re: Spread aluminium frame to 150mm?

Post by eCue » Jun 16 2018 11:48pm

Try bending it :D
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qwerkus   100 W

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Re: Spread aluminium frame to 150mm?

Post by qwerkus » Jun 17 2018 3:56am

I think it's a common misconception that you can't spread aluminium frames. The proper way to do it would be to anneal the material back to a T4 state where it can easily be bent, and than heat treat it back to full T6. If you know someone with an oven, that's what I would recommend. Simple 200°C Oven (actual temp depends on the alloy, as will be around 150° short or 60° long) with controlled temperature will do the trick; if you don't weld anything, there is no need for an expensive solution treatment + quenching. Not doable with a powdered coating, as it will melt and make a mess, but no problem with anodized aluminium.

When it comes to cold working, like MadRhino said: it depends on the tube shape and the type of aluminium. A guy at DT's told me that most aluminium rims are cold worked into the final shape to save costs !
5083 is best for cold working and will actually gain strength. 7005 is pretty stiff. 6061 is best for bending / forming, but usually comes in too thin tubes to save weight. Cheap commuting bicycles with heavy frames are easiest. Usually they are not fully hardened to T6 state, but "container hardened" during shipping.

Also, if you are up to a little modding, I think that motor can be narrowed down to 135-140mm, by using a small freewheel and a rim brakes. In most case modding the hub gives better results than bending the frame, because you can do a better centering job.

cwah   10 GW

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Re: Spread aluminium frame to 150mm?

Post by cwah » Jun 18 2018 6:58am

Here's how the motor look like:
https://www.dropbox.com/s/0br6ec5moz13a ... 3.jpg?dl=0

Dimension:
https://www.dropbox.com/s/ecwmmofgfccim ... 2.png?dl=0

Can it be trimmed down easily to 135mm?
Help me find my stolen electric brompton: http://bit.ly/1a0vbBC and Bosch Sinus B3 http://bit.ly/1eV0WQz

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Chalo   100 GW

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Re: Spread aluminium frame to 150mm?

Post by Chalo » Jun 18 2018 10:42am

cwah wrote:
Jun 12 2018 10:32am
It also has a casted wheel like this one:
http://www.cnqsmotor.com/en/article_rea ... r/487.html

So no more fiddling with spokes, wheels out of shape and broken spokes.
That wheel can get bent out of shape for sure (and even break spokes), but when that happens there will be nothing you can do about it.

Yes, it is simpler. Sometimes being simpler means throwing a thing away when it could otherwise have been repaired.
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markz   100 GW

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Re: Spread aluminium frame to 150mm?

Post by markz » Jun 18 2018 3:51pm

MadRhino wrote:
Jun 12 2018 7:46pm
Or build the width with custom dropouts. That, is the proper way to do it.
That would be cool to do, especially for the MXUS 5000W motor.

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