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Lengthening A Motomag Frame Build:  RSS Feed

#26 2017-03-08 6:16pm

RobS
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From: Mountain View CA
Registered: 2014-05-10
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Re: Lengthening A Motomag Frame Build:

I don't think the seat tube angles will be right, if that's where youre going to cut it, they may be to low when you reweld them


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I'm no body builder, but I do 12oz tilts daily!!

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#27 2017-03-08 6:38pm

Shotgun
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From: Tortugas Pines
Registered: 2014-03-09
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Re: Lengthening A Motomag Frame Build:

RobS wrote:

I don't think the seat tube angles will be right, if that's where youre going to cut it, they may be to low when you reweld them

I am going to replace the seat tube as well as both front tubes so the angles will be correct. I am not going to just lengthen the upper and lower tubes, they will be replaced completely.

Last edited by Shotgun (2017-03-08 6:41pm)

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#28 2017-03-09 5:31am

BritUS
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From: Maine
Registered: 2011-04-18
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Re: Lengthening A Motomag Frame Build:

Great project - I'm in. smile


The true measure of a mans worth, is what he would do if he knew he would never be caught.

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#29 2017-03-09 5:37pm

Shotgun
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From: Tortugas Pines
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Re: Lengthening A Motomag Frame Build:

No turning back now:
http://uploads.bmxmuseum.com/user-images/207817/img_484458c203217b.jpg
http://uploads.bmxmuseum.com/user-images/207817/img_484358c20321bb.jpg

http://uploads.bmxmuseum.com/user-images/207817/img_484558c203492e.jpg
http://uploads.bmxmuseum.com/user-images/207817/img_484958c2034c52.jpg
http://uploads.bmxmuseum.com/user-images/207817/img_484858c2034ce9.jpg
http://uploads.bmxmuseum.com/user-images/207817/img_484658c2034d1b.jpg
http://uploads.bmxmuseum.com/user-images/207817/img_484758c2034d5d.jpg

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#30 2017-03-09 5:55pm

BritUS
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From: Maine
Registered: 2011-04-18
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#31 2017-03-09 5:55pm

sting bmx
Banned
Registered: 2016-07-01
Posts: 501

Re: Lengthening A Motomag Frame Build:

Shotgun wrote:

Ok, so now for a little metallurgy. No matter what you have been told, chrome moly is NOT lighter than steel!! Chrome moly is steel plain and simple, it is not a different metal. A piece of chrome moly and a piece of mild steel with the exact dimensions weigh exactly the same!! Chrome moly is steel that has about 20% more carbon in it giving it more tensile strength. Since it has more tensile strength and is therefore slightly stronger, it can have a thinner wall thickness and be just as strong as a thicker walled piece of mild steel tubing. This is where the weight savings come from.

Chrome moly can be arc welded, brazed, oxy-acetylene (gas welded) Mig welded and TIg welded. TIg is the process that is used the most on chrome moly since it looks neater for items such as bicycles.

mig weld looks nice on anything ..i never knew you can weld bike frames with mig or stick (7018)...i been welding stick ,mig and flux core 25 years on skyscrapers ..but nice to know you can weld chromolly with mig n stick on a bike frame

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#32 2017-03-09 6:00pm

Shotgun
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From: Tortugas Pines
Registered: 2014-03-09
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Re: Lengthening A Motomag Frame Build:

Haha, I didn't meant you could stick weld on a bike frame, but Mig on a bike frame no problem.

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#34 2017-03-09 6:05pm

sting bmx
Banned
Registered: 2016-07-01
Posts: 501

Re: Lengthening A Motomag Frame Build:

Shotgun wrote:

Haha, I didn't meant you could stick weld on a bike frame, but Mig on a bike frame no problem.

ya stick would be messy i bet ..but we do alot of pipe rails and we use the mig for that

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#35 2017-03-19 12:08pm

Shotgun
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From: Tortugas Pines
Registered: 2014-03-09
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Re: Lengthening A Motomag Frame Build:

I filled in the gouges on the drop outs and the left chain stay and ground them smooth:
http://uploads.bmxmuseum.com/user-images/207817/img_489658ced6415e.jpg
http://uploads.bmxmuseum.com/user-images/207817/img_489558ced64157.jpg

I re-used one of the tubes as the new seat tube and notched it to fit with a 2 1/4" hole saw:http://uploads.bmxmuseum.com/user-images/207817/img_489258ced6b415.jpg
http://uploads.bmxmuseum.com/user-images/207817/img_489058ced6b3f3.jpg
http://uploads.bmxmuseum.com/user-images/207817/img_489158ced6b42b.jpg

I cut the tube to length and cut a new slot at the top of the tube:http://uploads.bmxmuseum.com/user-images/207817/img_489358ced71b67.jpg
http://uploads.bmxmuseum.com/user-images/207817/img_489458ced71b63.jpg

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#36 2017-03-19 4:03pm

BritUS
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From: Maine
Registered: 2011-04-18
Posts: 1471
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Re: Lengthening A Motomag Frame Build:

Nice smile


The true measure of a mans worth, is what he would do if he knew he would never be caught.

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#37 2017-03-19 9:01pm

Shotgun
Pro Member
From: Tortugas Pines
Registered: 2014-03-09
Posts: 1121
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Re: Lengthening A Motomag Frame Build:

I started welding on it today:

http://uploads.bmxmuseum.com/user-images/207817/img_489758cf540e64.jpg

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#38 2017-03-19 9:31pm

Crashman
BMXer 4 Life
From: Mount Pleasant, MI
Registered: 2012-04-22
Posts: 4695
Bikes: 2

Re: Lengthening A Motomag Frame Build:

Shotgun wrote:

RobS wrote:

to make it longer, doesn't the head tube have to go up almost as much as you stretch the frame?

I am just going to slide it forward and see how it looks.

I have a solution that allows you to preserve the factory welds on the gusset. Add 2" to the factory tubing, and weld the downtube lower on the bottom bracket shell like Redline did. You'll only be moving the headtube up around .03" that way, and if you're worried that setting it back down on factory forks will result in too much head tube angle...you can always lengthen the downtube 1/4" more than the top tube. It will also result in the bottom bracket sinking about half the distance the head tube is raised once the bike is put together.


Wanted: Inexpensive lot of cheap 7/8" bars for grandkid's bikes. I will paint as needed.

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#39 2017-03-19 9:33pm

Crashman
BMXer 4 Life
From: Mount Pleasant, MI
Registered: 2012-04-22
Posts: 4695
Bikes: 2

Re: Lengthening A Motomag Frame Build:

Crashman wrote:

Shotgun wrote:

RobS wrote:

to make it longer, doesn't the head tube have to go up almost as much as you stretch the frame?

I am just going to slide it forward and see how it looks.

I have a solution that allows you to preserve the factory welds on the gusset. Add 2" to the factory tubing, and weld the downtube lower on the bottom bracket shell like Redline did. You'll only be moving the headtube up around .03" that way, and if you're worried that setting it back down on factory forks will result in too much head tube angle...you can always lengthen the downtube 1/4" more than the top tube. It will also result in the bottom bracket sinking about half the distance the head tube is raised once the bike is put together.

BTW, I personally would go even on the top tube and downtube lengths, a little extra head tube angle isn't going to hurt you.


Wanted: Inexpensive lot of cheap 7/8" bars for grandkid's bikes. I will paint as needed.

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#40 2017-03-19 9:33pm

James Vigil
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From: HWD, Ca.
Registered: 2008-11-02
Posts: 2518
Bikes: 2

Re: Lengthening A Motomag Frame Build:

cool


A pile of shit has a thousand eyes.

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#41 2017-03-19 9:50pm

Shotgun
Pro Member
From: Tortugas Pines
Registered: 2014-03-09
Posts: 1121
Bikes: 48
For Sale: 11

Re: Lengthening A Motomag Frame Build:

Crashman wrote:

Shotgun wrote:

RobS wrote:

to make it longer, doesn't the head tube have to go up almost as much as you stretch the frame?

I am just going to slide it forward and see how it looks.

I have a solution that allows you to preserve the factory welds on the gusset. Add 2" to the factory tubing, and weld the downtube lower on the bottom bracket shell like Redline did. You'll only be moving the headtube up around .03" that way, and if you're worried that setting it back down on factory forks will result in too much head tube angle...you can always lengthen the downtube 1/4" more than the top tube. It will also result in the bottom bracket sinking about half the distance the head tube is raised once the bike is put together.

These head tube, and gussets are already cut apart at this point. Both the top and bottom tubes had dings and dents, that is why I am replacing them entirely. I would like to see your solution though.

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#42 2017-03-19 10:22pm

BRICKOS2
Pro MemberTHIRSTY
From: SoCAL
Registered: 2013-07-14
Posts: 5164
Bikes: 13
For Sale: 26

Re: Lengthening A Motomag Frame Build:

Those welds looks fantastic smile

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#43 2017-03-20 9:37am

AlurencatBMX
Pro Member
From: West Sussex UK
Registered: 2010-04-09
Posts: 1539
Bikes: 6

Re: Lengthening A Motomag Frame Build:

Stellar work sar, I doff my cap.


If you haven't seen the magical stars floating around whilst lying face down in the mud you ain't lived.

Skyways for show, spokes for go.

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#44 2017-03-20 6:22pm

Shotgun
Pro Member
From: Tortugas Pines
Registered: 2014-03-09
Posts: 1121
Bikes: 48
For Sale: 11

Re: Lengthening A Motomag Frame Build:

Got a little more done today:
http://uploads.bmxmuseum.com/user-images/207817/img_490058d07f4dde.jpg
http://uploads.bmxmuseum.com/user-images/207817/img_490158d07f9656.jpg
http://uploads.bmxmuseum.com/user-images/207817/img_489858d07f971a.jpg

Just to ruffle some feathers, I went ahead and Mig welded the seat brace:
http://uploads.bmxmuseum.com/user-images/207817/img_489958d08016e6.jpg

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#45 2017-03-20 6:56pm

ritchiecamaro
Pro Member"Fistin' Britney"
From: Battle Creek, MI
Registered: 2011-03-30
Posts: 3145
Bikes: 58
For Sale: 3

Re: Lengthening A Motomag Frame Build:

That's coming along nicely... Top-notch work!!! big_smilebig_smilebig_smile


420 for LIFE!!!

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#46 2017-03-20 7:43pm

thesega
Pro MemberLOWBALLER FO' LIFE!!
From: Texas
Registered: 2009-12-15
Posts: 3352
Bikes: 8
Website

Re: Lengthening A Motomag Frame Build:

cool


I always hated when people Split the F/F. The Fork goes to that frame So why split it?
true ballers only ride proto-types
"This show is stupid, Turn it up louder"
jimmybills: 'costco broke my glove box'

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#47 2017-03-20 9:12pm

Saohagan
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From: Houston, Tx
Registered: 2017-01-29
Posts: 269
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For Sale: 4

Re: Lengthening A Motomag Frame Build:

cool

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#48 2017-03-21 8:39am

skdevore
Pro MemberIt's Not For Sale, Francis!
From: Claremont, CA
Registered: 2010-04-30
Posts: 3619
Bikes: 29

Re: Lengthening A Motomag Frame Build:

Nice work.


There's no help for this Museum Junkie!

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#49 2017-03-21 9:47am

stonie
Pro MemberThe Museum Therapist
From: Boise
Registered: 2008-07-16
Posts: 9818
Bikes: 2
For Sale: 48

Re: Lengthening A Motomag Frame Build:

Rad, can't wait to see the end result           smile


Gnarly is when it's beyond radical, it's balls out danger, & or perfection, & or skill or all of that combined. Nobody can shred like that guy, he's gnarly.                                        \m/  ( º . º )  \m/
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#50 2017-03-21 10:32am

BDUBinVegas
Pro Member
From: Las Vegas
Registered: 2013-03-06
Posts: 484

Re: Lengthening A Motomag Frame Build:

awesome


The more people I meet the more I like my dog.

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