Fabricating a sissybar... help please.

[InsolentMinx]

Happy New Year all!

A little help/advice please?

I have some questions for those of you with some expertise in metal fabrication and metal strengths.

I quite like the idea of a sissybar as I want to start taking my gf on the bike with me when the weather clears up, and i don't like the idea of her having to continually keep a tight hold on to me (as nice as it is) as my aftermarket seat doesn't have a grab strap like the original did.

I won't be using my bike as a long distance 2up tourer, so I just want something to provide a little extra security for my gf incase she wants to relax her grip on me without fear of toppling off backwards if i suddenly accelerate  

Thing is, I have 2 main issues.

1. I don't want it to be permenantly attached to the bike.
2. It has to be compatible with my EasyBracket mounting posts (see pic).

I've only found 1 detatchable sissybar on sale and that requires the complete replacement of the plasti-chrome fender trim and installation of an EasyBracket-style bolt.
I'm also a little put off by the $250 price for what is effectively a few flat pieces of metal with holes in and an upright bent piece with a cushion attached.

I took a couple of measurements and found a 1-2mm gap between the inside of the EasyBracket bolt and the plastic fender trim.

I was thinking of a flat mounting plate with 2 right angle 'channels' in it.
This would allow you to drop the sissybar unit onto the EasyBracket bolts, and then you push it backwards so it latches on to the bolts and secures it in place.

I'm just wondering if a design like this is going to be strong enough to support a female form reclining against it without bending or snapping?
She's only 5'0" and I'm not stupid enough to ask how much she weighs, but she's pretty small.
I obviously want it to be sturdy incase i take passengers who are bigger too.

Looking at one website Metals4u, prices seem very reasonable for a metre of steel rod and steel plate.
I'm thinking a 18 or 20 mm diameter stainless or mild steel rod as the sissybar itself, and then a 1 or 2 mm thickness mild steel plate for the mounting 'bracket'.

Would there be a difference between stainless steel (316) or mild steel in it's strength?
CobraUSA make their 'round' sissybars from 3/4" High Strength Steel rods.
Would that be the same as mild steel?

It wouldn't really be for leaning back against and relaxing, just more of a "ooh crap!... i'm glad that was there to stop me toppling off backwards while i scratched my arse"; and to keep her within reach in case she does lean back a little too far.

To finish, I'd probably give it a few coats of flat black paint, or a gloss black and clearcoat. Or maybe even pay to get it powdercoated.

My girlfriend's dad is a builder and I'm told he can fabricate and has a MIG welder, so i could ask/pay him to make it for me if it's going to be a viable solution to my problem.

Any help would be greatly appreciated.

Fabricating a sissybar... help please.

hmmm, sorry, i tried to attach it, but the file's too big... and when i add it as a picture, the text is too hard to read
well, you get the gist i hope. the text is pretty much what i've written here anyway.

[tbone]

20mm bar will be more than capable of doing what you it too, for your mounting plates i`d be looking at 2 or 3mm plate if possible, dont use 1mm. If your gonna paint or powdercoat then go with mild not stainless, theres plenty of strength in the steel. My concern would be that you say it would bolt to a plastic fender, think i would make up a metal plate to sit on the inside of your fender that your Easybracket posts mount to.

[InsolentMinx]

Thanks for the reply tbone.

I couldn't sleep that night, so lay awake and thought that an angled slot (see pic) would probably be better than the L shaped slots so the unit can just 'drop' onto the bolts, which might be more secure as it should resist movement in pretty much all directions once the unit is in place.

Fabricating a sissybar... help please.

The bolts themselves are threaded into a metal strut under the plasti-chrome trim. It's this strut which the fender itself is mounted to. It's part of the frame of the bike, so it's plenty rigid. I think i may put a spacer in under the plasti-chrome trim to push the EasyBracket bolts out a mm or two to give me more space so it can accommodate a 3-4mm plate.

I also thought i might "beef up" to maybe a 30mm bar juuust in case

A guy on another bike forum said he could cut me out the side plates with a CNC machine he works on... I might draw up some templates on corrugated cardboard at the weekend and see how that works out for fitment.

I also thought of adding a cross bar at the base of the unit which would provide added support and resist any possible twisting in the structure.
So from behind it would look like a caplital A: A

[tbone]

Again, your angled slots would work and would be easier to fit and remove ( if thats a good thing?).  I still say that your drawings in 20mm bar will be ok, unless you plan on a really tall bar you shouldn`t need an extra brace, although you may have to fit one to mount the pad? . Take a good look at 30mm stuff, its huge! If you can squeeze 4mm for the plate then go for it but remember that the forces acting on it will be along the length of the plate not the width.

[InsolentMinx]

you're right, i've not really knowingly seen 30mm before.  I don't want the thing to be too imposing.

Yeah, i suppose the ease of removal could be an issue if it becomes easy to remove whilst in use at 40mph should she shuffle a little and the back of her jacket rubs/catches against it.

oh, a pad...  i forgot about that 
I thought about a small floral frilly cusion and some duct tape ... 
or maybe find a small leather pad which has a sleeve on the back and just slides down over the bar and rests in place at the bottom where the design flares out and widens to meet the plates...

I think i'll aim for 3mm plate and a 20mm bar. I don't want the back to be too tall, but I'd like it to be tall enough to stand and strap a small camping rucksack to. so maybe 40cm above the seat? Dunno, i'll have to get the tapemeasure out at the weekend and draw up some proper plans.

Oooh, how exciting... my first attempt at a proper design and customisation!

[tbone]

Heres one i did many moons ago, 20mm bar if i remember correctly, don`t think i`d go for anything that tall again tho 

[InsolentMinx]

cool. thanks alot tbone, you've been very helpful

[BikerGran]

I don't think they look good too tall, also I can't say I like the ones that come to an inverted 'V' - but it's all a matter of personal taste.

[Manky Monkey]

Plenty of scope for creativity though -seen the pointy bit finishing in devil's tails & the like.

[InsolentMinx]

yeah, i'm not sure i'd have it coming to a point at the top...It could look good with a slightly rounded point, but also possibly a little dangerous
I'd most likely have it flat; a bit like the top-middle design (#2) on my original post.
I hadn't really considered an ornate design for the backrest, i figured something simple would be the best bet. I don't really have any theme (as such) for the bike, so a Maltese cross might look a little out of place, same with a skull, etc. I have a few 'flame' items, but they're quite subtle. Not sure I'd like a flame shaped backrest (as cool as it would be) .... i think something modest yet slightly aggressive would be good, and i think that number 2 design fits the bill. Plus it's easy to make.

I did more doodling in the office today (work is non-existant) and i came up with this idea for the side plates.
The slot angle has been changed. the front slot would slide onto the front bolt horizontally, and then the back slot would just drop down onto the back bolt. There's then a regular cam tumbler lock, which rotates around into place securing the unit against the rear bolt and restricting any upward movement whatsoever.
 
Maplin actually sell one which is designed for installing on anything with a thickness up to 4mm, so would be perfect for my 3mm sheet steel. I'd just pad out the exta mm with a washer/spacer if need be.

[Manky Monkey]

Sounds like you're a lot more organised than most of us here! A man with a plan.
Go for it. 

[InsolentMinx]

haha, thanks for the vote of confidence.

I work for a ship operator, and the shipping market is pretty dead right now. I'm still in training, so my while boss is looking for business, but i'm just sat around the office studying for my shipping exams... well... more procrastinating at the moment.

I'm really excited about this project as it's my first real attempt at properly designing something outside of the woodwork class in school for GCSE.

Sadly I won't be able to do much of the actual fabrication myself due to lack of skill and tools, but I heard from a guy in another forum who has access to a CNC machine and said if i get him a template he can cut the side plates for me... and i'm hoping i'll be able to take an active part in making the actual backrest part from the steel rods with my girlfriend's dad. ... but i've not mentioned it to him yet, so that bit will wait.

I can do the side plate templates on my own though. So might do that on Sunday if i have the time.

But it's great to have those little words of encouragement from guys and gals like you all who've been working with metal and machinery for many years.    if there was a 'thumbs up' icon, i'd use it!

[Manky Monkey]

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[InsolentMinx]

that's the one! 

Fabricating a sissybar... help please.

[InsolentMinx]

It'd look something like this i think/hope.
The image is more bias towards the side plates as it's hard trying to draw 3D in Paint, but it gives an idea.
I just hope the actual sissybar itself will look a little more integrated into the styling and shape of the bike... although i guess i won't know until building starts.

Fabricating a sissybar... help please.