I will start off by saying that this is intended to be quite a long build as it gives me and my old man something to do in terms of a hobby. Having read lots of other projects I thought I might document mine also.
I have built a Moto Guzzi V50 racer previously and almost finished a restoration of a 1990 ZXR750...the latter has a frustrating fuelling issue that I will be getting a professional to look. In the meantime the Bandit build has started.
the other thing that has just occurred to me is that i may have clearance issues with turnbuckles as a final solution. gonna have to think this through. got some flat bar this week so will drill random holes and see how we go.
Yet again i am back pondering what to do in terms of subframe. At first i thought weld a new tube subframe although after putting frame slugs in there would need to be an immediate bend in the subframe to avoid a very flat seat. I think this might be too difficult.
So, i am thinking about doing something like in the photo by cutting the frame further back, weld something to close the gaping holes up and then weld on some 10mm tabs with holes so i can bolt the subframe on. I wont be doing the welding however.
Getting really stuck with this now...any clarity greatly appreciated...paint or photoshop for my simple brain might help or just links that pictorially make sense to someone new to fabrication.
get it on its wheels, put the tank on and place the seat unit where it needs to be, that'll give you a better idea when making subframe , and where mounts need to be
Wishing i hadn't painted the tank now...should have waited until mock up was complete. Doh!
I shall just have to be careful with it though it might have to wait a while due to a torn medial meniscus in my knee limiting moving about for fuck's sake.
And the bloody bike lift didn't turn up today...Monday they say...fucking brilliant.
Replacement bike lift arrived and working as it should...knee still fucked but could be worse.
Forks and front wheel in next. Need to do more sanding on forks as the slightly ribbed texture can be seen in places. Then they are gonna be polished but not highly so.
Then i can see if i cant mock up what the subby will look like. I have a better idea on how to do that now by purchasing tubes with different degree bends in them to find the right one.
Thats the next bit. now it's on its wheels and settled on the suspension i am going to try and work out what angle the seat needs to be at.
Very rough mock up today looked right but will have a better idea when i straddle it. Ordered some renthal medium superbike bars. Will be able to get an idea as to the height risers i will need and get them ordered. Not sure how easy that will be without something proper to sit on...any suggestions welcomed cos all i can see is me floating in mid air!
Will also know if my peg mounts are in a good position or not.
Aye it's taking shape. Been searching in the web for pre bent mild steel tubing...wish i had saved the bloody page now as i found a supplier who had various degree bends in lengths of tube. Anyone know of such a place please feel free to end my internet suffering...i just want to try different angles out.
Or buy a pipe bender, depending on how much you spend you can get a good one for 20-25mm tube or a cheeper hand one and mock something up in smaller pipe. You can then bend it to what you want, then get some proper pipe/tube to the angles you want.
I was looking at some pipe benders last night and thinking that might be the way forward...i shall check what size tube i need and see if i can get a cheap one.
Just be careful as a pipe and tube do not have the same OD for a given nominal size. That means the dies on a pipe bender are going to have a larger ID than those for a tubing bender. If you’re only doing small bends it may not matter but for sharper bends tubing may kink.
Think Yan explained that to me some time back...good to be reminded before i go and buy one...however if i can find this place that sold pre bent tubes in mild steel for a short-ish length it would save a few quid. There's plenty selling stainless, mostly for exhausts but i need mild. It did cross my mind to see if there’s anything made from carbon fibre out there...probably a good reason why i ain't seen no carbon subframes on the net!
So i have done a little mocking up for seat angles etc. Thinking top rail is only like 10° and the bottom 25°...this might change of course when I try it for size.
Not sure yet how long the tubes need to be as I don't necessarily need the subframe right to the very edge of the back of the seat. That will depend upon the location of the rear light and winkers.
Any comments as to any pitfalls i may not be seeing appreciated.
I looked up automotive racing roll cages from a big racing product store here in the US (Summit Racing). Most of the cages they sell are 1.625” (41.3mm) x 0.120” (3mm) in DOM mild steel.
What your supplier is offering for wall thickness is overkill for a subframe. 0.65-0.83” (1.65-2.1mm) would be fine IMO. Maybe Yantosh can chime in?
You are right I am sure Doug...have gone ahead as the top rails are 3mm so just continuing with what Suzuki built it with. But...it does seem to be chunky stuff.
weld bungs into frame with threaded holes, use rose joints to attach the subframe to. Send me 4 bits of tube if you want, i will bend them , few weeks and my shed should be empty enough for work
Thanks Yan...will put some pics up when tube gets here...sent guy a crap drawing to know where to stick the bends...if all goes fuckery i shall be in touch with you to rescue me!
Tell me more about the threaded bungs idea please amd the rose joints...remember my brain doesn't speak engineer...visuals better. I did originally want a detachable subframe but didnt think i could pull it off. I do have a professional welder on my team should i need one.
Oh i see. Some round bar, tapped and maybe even weld a captive nut at the back and then weld to the frame. Hmmm...this may be a good back up plan...thanks Yan.
doing it that way, weld the nut to the round bar, drill through the nut, then tap through the nut, to give one thread. Or drill the round bar, use the tapping drill to align the nut while welding and then tap through the nut.
My Renthals turned up so just clamped them on the top yoke to see what height risers i will need...looking likely eother 30mm or 40mm. I am gping to try and perch myself over the bike in some kind of seating position, get my motorcycle hating wife to take some photos so i can get an idea visually and by feel whether the peg mounts i made are too far back...if they are i have some wiggle room to adjust.
Whilst i wait for tube to turn up i have been given a propane garage heater i am going to give some love to.
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