# need an engineer's opinion **URL:** \ **Category:** NYSpeed Automotive\ **Created:** [October 21, 2007, 5:09pm UTC](https://forums.speedlife.net/t/need-an-engineers-opinion/37345 "2007-10-21T17:09:18Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![woz](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/woz/32/7605_2.png) [@woz](https://forums.speedlife.net/u/woz)\ **Post date:** [October 21, 2007, 5:09pm UTC](https://forums.speedlife.net/t/need-an-engineers-opinion/37345/1 "2007-10-21T17:09:18Z")
ok so im considering turning the 900 i just picked up into a streetfighter and i want to shorten the tail if i do. ![http://i28.photobucket.com/albums/c230/originalsin1087/DSC01115.jpg](http://i28.photobucket.com/albums/c230/originalsin1087/DSC01115.jpg) what im thinking is just cut the current subframe and shortening each member then welding back together, as drawn in the pic below. obviosuly i would have it professionally welded. ![http://i28.photobucket.com/albums/c230/originalsin1087/idea.jpg](http://i28.photobucket.com/albums/c230/originalsin1087/idea.jpg) but does this seem safe? thats my main concern another idea was just hacking the rear right off and welding another brace in to connect the gap between the upper and lower ---
**Author:** ![BrockwayMT](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/brockwaymt/32/5060_2.png) [@BrockwayMT](https://forums.speedlife.net/u/BrockwayMT)\ **Post date:** [October 23, 2007, 1:59pm UTC](https://forums.speedlife.net/t/need-an-engineers-opinion/37345/2 "2007-10-23T13:59:00Z")
Looks ok to me with a good crossmember at the end. How are you going to mount the 12 oclock bar though if you cut the subframe off? ---
**Author:** ![woz](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/woz/32/7605_2.png) [@woz](https://forums.speedlife.net/u/woz)\ **Post date:** [October 23, 2007, 2:29pm UTC](https://forums.speedlife.net/t/need-an-engineers-opinion/37345/3 "2007-10-23T14:29:22Z")
im not building it to stunt im also trying to think of a way to make a little tail light housing that mounts above the seat a bit if i dont do that the light will go below the back of the seat and the back of the seat would be a straight drop to the rear hugger im going to put on ---
**Author:** ![Carnut](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/carnut/32/7590_2.png) [@Carnut](https://forums.speedlife.net/u/Carnut)\ **Post date:** [October 23, 2007, 2:32pm UTC](https://forums.speedlife.net/t/need-an-engineers-opinion/37345/4 "2007-10-23T14:32:19Z")
I am not an engineer. However. Based on the fact that the material there is used to support the weight of 2 people at that distance from where it is bolted…I would assume that if the piece you make mimics the current design but is shrunk in scale to fit the single seat it should work fine. It would then only have to support one persons weight and you are using the same material with the current material dimensions. if you are building that streetfighter like you showed me that is awesome. ---
**Author:** ![93dx\_hatch](https://avatars.discourse-cdn.com/v4/letter/9/90ced4/32.png) [@93dx\_hatch](https://forums.speedlife.net/u/93dx_hatch)\ **Post date:** [October 23, 2007, 2:34pm UTC](https://forums.speedlife.net/t/need-an-engineers-opinion/37345/5 "2007-10-23T14:34:34Z")
I’m not an engineer. However. I would like to see a pic of the whole bike to see if it will still look proportionate ---
**Author:** ![somedude](https://avatars.discourse-cdn.com/v4/letter/s/ecd19e/32.png) [@somedude](https://forums.speedlife.net/u/somedude)\ **Post date:** [October 23, 2007, 2:57pm UTC](https://forums.speedlife.net/t/need-an-engineers-opinion/37345/6 "2007-10-23T14:57:28Z")
dirt/water/rubber spray off the rear tire? ---
**Author:** ![Carnut](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/carnut/32/7590_2.png) [@Carnut](https://forums.speedlife.net/u/Carnut)\ **Post date:** [October 23, 2007, 3:10pm UTC](https://forums.speedlife.net/t/need-an-engineers-opinion/37345/7 "2007-10-23T15:10:33Z")
![http://www.rrzone.com/forums/attachment.php?attachmentid=163&d=1152863343](http://www.rrzone.com/forums/attachment.php?attachmentid=163&d=1152863343) ---
**Author:** ![woz](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/woz/32/7605_2.png) [@woz](https://forums.speedlife.net/u/woz)\ **Post date:** [October 23, 2007, 3:29pm UTC](https://forums.speedlife.net/t/need-an-engineers-opinion/37345/8 "2007-10-23T15:29:56Z")
wrd, don beat me to it. my idea is a bit different. a bit diff paint scheme keeping the clip ons using an f4i guage cluster different exhaust have mirrors and front signals one more pic ![http://k53.pbase.com/v3/95/185295/1/46301224.BR_0167.jpg](http://k53.pbase.com/v3/95/185295/1/46301224.BR_0167.jpg) ---
**Author:** ![Carnut](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/carnut/32/7590_2.png) [@Carnut](https://forums.speedlife.net/u/Carnut)\ **Post date:** [October 23, 2007, 3:34pm UTC](https://forums.speedlife.net/t/need-an-engineers-opinion/37345/9 "2007-10-23T15:34:16Z")
You wanna just buy your old bike back 😛 ---
**Author:** ![woz](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/woz/32/7605_2.png) [@woz](https://forums.speedlife.net/u/woz)\ **Post date:** [October 23, 2007, 3:37pm UTC](https://forums.speedlife.net/t/need-an-engineers-opinion/37345/10 "2007-10-23T15:37:01Z")
lol nope. this will way more rad than that ---
**Author:** ![LAFENGAS](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/lafengas/32/7573_2.png) [@LAFENGAS](https://forums.speedlife.net/u/LAFENGAS)\ **Post date:** [October 23, 2007, 3:48pm UTC](https://forums.speedlife.net/t/need-an-engineers-opinion/37345/11 "2007-10-23T15:48:41Z")
IMO, it looks fine. If you keep the geometry and materials the same, you will be able to support even more weight then originally designed, because the cantilever will have been shortened. ---
**Author:** ![Violator](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/violator/32/7278_2.png) [@Violator](https://forums.speedlife.net/u/Violator)\ **Post date:** [October 23, 2007, 3:49pm UTC](https://forums.speedlife.net/t/need-an-engineers-opinion/37345/12 "2007-10-23T15:49:40Z")
that will support you just fine. I would recommend that you tell the welder that this is structural. I dunno what alloy that is but I would stress relieve the weld if possible. ---
**Author:** ![Carnut](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/carnut/32/7590_2.png) [@Carnut](https://forums.speedlife.net/u/Carnut)\ **Post date:** [October 23, 2007, 3:51pm UTC](https://forums.speedlife.net/t/need-an-engineers-opinion/37345/13 "2007-10-23T15:51:21Z")
[quote=“originalsin,post:10,topic:37345"”] lol nope. this will way more rad than that [/quote] You would say that. [quote=“LAFENGAS,post:11,topic:37345"”] IMO, it looks fine. If you keep the geometry and materials the same, you will be able to support even more weight then originally designed, because the cantilever will have been shortened. [/quote] That’s what I was thinking. ---
**Author:** ![Dr.Stevil](https://avatars.discourse-cdn.com/v4/letter/d/da6949/32.png) [@Dr.Stevil](https://forums.speedlife.net/u/Dr.Stevil)\ **Post date:** [October 23, 2007, 4:54pm UTC](https://forums.speedlife.net/t/need-an-engineers-opinion/37345/14 "2007-10-23T16:54:54Z")
I don’t see why it wouldn’t work ok… although I’d have a hard time cutting up a fairly new bike to reduce the seat length ---
**Author:** ![woz](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/woz/32/7605_2.png) [@woz](https://forums.speedlife.net/u/woz)\ **Post date:** [October 23, 2007, 4:56pm UTC](https://forums.speedlife.net/t/need-an-engineers-opinion/37345/15 "2007-10-23T16:56:22Z")
the bike is 10yrs old… but im thinking i may fab up a 2nd short subframe, rather than hacking the stock one up ---
**Author:** ![Dr.Stevil](https://avatars.discourse-cdn.com/v4/letter/d/da6949/32.png) [@Dr.Stevil](https://forums.speedlife.net/u/Dr.Stevil)\ **Post date:** [October 23, 2007, 4:58pm UTC](https://forums.speedlife.net/t/need-an-engineers-opinion/37345/16 "2007-10-23T16:58:13Z")
shit, in that case, go for it if you don’t like it, you can just revert back :tup: ---
**Author:** ![BrockwayMT](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/brockwaymt/32/5060_2.png) [@BrockwayMT](https://forums.speedlife.net/u/BrockwayMT)\ **Post date:** [October 24, 2007, 5:48pm UTC](https://forums.speedlife.net/t/need-an-engineers-opinion/37345/17 "2007-10-24T17:48:30Z")
[quote=“Carnut,post:4,topic:37345"”] I am not an engineer. [/quote] thank God! 😉 ---
**Author:** ![vt1992s10](https://avatars.discourse-cdn.com/v4/letter/v/73ab20/32.png) [@vt1992s10](https://forums.speedlife.net/u/vt1992s10)\ **Post date:** [October 24, 2007, 6:04pm UTC](https://forums.speedlife.net/t/need-an-engineers-opinion/37345/18 "2007-10-24T18:04:01Z")
no problem with that change, I would move the plate down towards the center more if that is possible. it would actually be stronger. Also make sure there is enough bracing between the sides to keep the side to side movement down. so 2 be an engineer 56 credit hours left. ~1 year ---
**Author:** ![Fry](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/fry/32/7284_2.png) [@Fry](https://forums.speedlife.net/u/Fry)\ **Post date:** [October 24, 2007, 6:33pm UTC](https://forums.speedlife.net/t/need-an-engineers-opinion/37345/19 "2007-10-24T18:33:09Z")
Although the idea of cutting anything structural on a sportbike makes me want to scream “Fuck no you hockey helmet short bus retard!” I don’t really see any problem with that. It’s just supporting the seat right? No suspension attachment points or anything else like that? ---
**Author:** ![woz](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/woz/32/7605_2.png) [@woz](https://forums.speedlife.net/u/woz)\ **Post date:** [October 25, 2007, 12:16am UTC](https://forums.speedlife.net/t/need-an-engineers-opinion/37345/20 "2007-10-25T00:16:48Z")
only suspension part that mounts to it is the rear shock remote res. or w/e and that just mounted with a small bracket that can be replicated. i think what i may do is keep the top member and make new, shorter lower ones. but yea its just the seat and the person welding it knows the application and will most likely be getting the bike as a whole so there are no fitment issues [Next page](https://forums.speedlife.net/t/need-an-engineers-opinion/37345.md?page=2)