Velocity Stacks

The stock ones are made out of Polypropylene, the same material as the rest of the airbox.

The dimensions are as follows:


It's also worth mentioning that the original stacks have almost no internal curve, it's pretty much just a straight taper.



If you could put a set of stacks inside of the airbox with the MWR filter then you may get the best of both worlds. I'm currently waiting on some ABS filament (ABS as it can be vapour smoothed to a polished finish using acetone vapours) for my 3D printer to arrive in the post and then I'm gonna print a set of stacks (modified to mount to the airbox). If they turn out good quality I'll fit them to my airbox and see how it looks. I won't test the airbox myself as I'd like to try my expensive stacks first however, if I can manage successfully print the stacks and I'm happy with the quality then I'll easily sell a pair of them for £5 + postage for anyone interested (designed to fit either the pod filters or airbox as required). It would also be possible for me to change diameter of the stack where the filter is mounted to allow other cheaper filters to be fitted.

 

This is my idea for mounting a stack to the airbox. Cut the original stacks out using a hole saw (60mm), fit an O-ring into the groove on the stack (They'll be the same size as the valve cover O-ring's, 63.17mm ID x 2.62mm, as I have a pile of 40 of them), drill the holes in the airbox and mount the stack using bolts. The transparent plate in the image is just for illustration.

 

Yea I'm a bit weary of it too but I figured I'd at least give it a shot and see how it turns out (however I think they should be perfectly fine for being mounted in the airbox as the airbox is supported with it's own mounts). I'll do some strength tests on it and make a tail tidy too to act as a fatigue test (to test for layer separation due to vibration, although the intake tubes would surely act as a damper since they're much more flexible compared to ABS). I know that WASP manufactures their PUK velocity stacks out of Acetal which I believe they CNC into shape (Also done some prototypes in printed pla, not functional ones though but still an interesting thread), so if I'm not satisfied with the ABS then I might purchase some Nylon/Carbon fibre composite filament as it seem's near indestructible and should be the closest thing properties wise compared to the acetal (Although it's around 5x the price of the ABS and a PITA to print) or maybe polypropylene.

I've printed a couple 1:2 scale stacks out of PLA material whilst setting up my printer and I'm really impressed by the strength especially considering I printed them using fast settings, I can't manage to break them using my hands even when applying pressure on just the inlet diameter. The vertical line + defect on filter mount base on the piece was caused by incorrect print settings and the line around the inner diameter was caused by incorrect assembly of the printer.



Also I was intending on increasing the mounting diameter of the filter up to 90mm as to make it easier to fit the filter to the stack, hopefully this'll make the stack stronger too (I've also added a chamfer + fillet between the tube mount and the rest of the stack to help better the stress distribution).




It's really generous of you to offer your manufacturing to others, and I'm sure you manufacturing stacks would still be much cheaper vs purchasing the "genuine" ones, it cost me 234$ (~£178) in total for mine including shipping + ~£18 import/handling fees.

 

Just run a stress simulation out of curiosity, the part was constrained around where it mounts to the intake tube (not really realistic since the intake tube will flex too) and a 100N point load was applied radially to where the filter mounts (to simulate the force exerted by the filter under acceleration). Considering the K&N RC-3250 weights 315g you'd have to be accelerating at 317 m/s^2 for it to experience this force (Unfortunately the hypermotard isn't this fast , max acceleration might be 10 m/s^2 at the most). Here's the results (max stress of 1.257MPa):

(worth mentioning that the simulation is presuming that the material is homogeneous which the 3D printed part will not be, although it should still give a good idea of the general stress concentrations and magnitudes throughout the part)

And here's some material properties of 3D printed ABS (Full PDF: https://www.innofil3d.com/wp-content/uploads/2016/05/TDS-Innofil3D-ABS-160609.pdf). The part will be printed vertically (therefore that's the important data).

So the part should theoretically be strong enough for the application, I'll be printing with 4 shells too, to ensure a nice finish with vapour smoothing (which should also help increase strength by increasing layer adhesion).

The biggest concern really is (as @mcantar mentioned) the glass transition temperature of ~105C, when the bike is operating this shouldn't be an issue (There's constant forced convection cooling from the air being drawn through the stack and also airflow around the outside). The main issue would be when you turn off the bike after a long run or perhaps when sitting in traffic in a warm country (AKA not the UK), will the heat from the engine be enough for it to reach 100C? I'm not sure. I'm making my bracket to hold the Idle/breather filters and coil out of ABS too, the coil will be mounted across the narrowest part so perhaps this could act as a test piece.
(printed in PLA for now, I had to make a few different versions until I managed to get the placement of the different components correct)

 

Just printed a full scale stack tonight using PLA, this stack is the one designed for a 90mm pod filter to be mounted such as this one: https://www.ebay.co.uk/itm/350837499211


It came out really well other than a small line that can be seen in the photo, although this was my fault (bashed the printer whilst printing) and it doesn't seem to compromise the structure as I'm able to push on it with both my hands as hard as possible without it breaking or bending.

My ABS should be arriving tomorrow so hopefully I'll get an ABS stack printed tomorrow!

 

I haven't been able to print any yet as I accidentally set the bed temperature of my printer too high which caused the print surface to peel off mid-print. I've ordered replacement parts but I haven't been at home for them to be delivered nor have I been able to pick them up due to work.

I have however ordered some Polypropylene filament to use if I'm not pleased with the ABS, the only downside to it is that it costs 6x that of ABS (£32 per 500G vs £32 for 3KG).

 

Good news, I managed to pick up my printer parts today (after being sat at the post office for 15 days). I fitted them tonight and printed a filter/coil bracket out of ABS. The ABS stuck really well to the bed, so well infact that I've had to put the bed in the freezer to get the part off. I'm pleased with how it turned out considering it's the first time that I've actually printed anything in ABS so I'll take my printer to work with me tomorrow and will hopefully get a stack made. (colours are a bit off in the photo, it's red not orange )

 

Also forgot to make a post about the Outerwears for the RC-3250's (Received them about a month ago), they fit spot on and look real nice too!