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Has anyone got the CAD or drawing that was generated for the Super Hawk intake trumpets? If so, please share. I intend to 3D print them (I've got a machine).
Yea, I know about this model but I was hoping to get the original and mess with it. Perhaps study the bell mouth dimensions and monkey with the mounting method.
I was all excited to see that there was a link to a file in your response (email notification). I did think it was a little strange that it was to the Grizzly site but hope springs eternal. Although, I'm beginning to suspect that I'm getting a 'no' from someone who can't say 'yes'.
Also, you have confounded the purpose of the internet! This is supposed to be a mecca for wish fulfillment and bench racing. I want to stand on the shoulders of GIANTS! not do the work myself.
Oh, well. Lets hope someone else who has the file responds. In the mean time I'll read a couple of papers on the subject.
The heat source is the carburetors. These are connected to the engine via rubber boots (a modest thermal insulator). The fuel that is pulled into them boils at ~200C so that's our upper temperature limit. The evaporation of the fuel as it enters the engine pulls some heat out of the carburetors. The air flowing into the airbox will always be at about atmospheric and has a heat capacity so it will be cooling the intake trumpets. Lastly, the engine is liquid cooled. My thermostat and fan switch keep my temperature readings below 88C (190F).
I think either thermoplastic would be fine. The print temperature is way higher than what the airbox would get to.
Although I intend to print on my Elegoo UV-Resin printer and the thermoset plastic should handle temperature even better.
I've been running some Felix Dellwood Stacks from Jesse Sculley (Aus) for over a year and 6k miles. They've seen everything from 32deg rides through the Sierra Nevada mountains to 112deg rides across the Mojave Desert. I have experienced nothing adverse. Well made, simple install. At first glance I thought the texture was a little rough. The dyno and use has proven no ill effect compared with my Dr. Honda billet replicas.
I found the science and arguments to be compelling. Also, they give a very concise formula for building your own bell mouth. Which I have done.
First article bellmouth. No method for bolting it to the airbox.
The recipe I followed is as follows:
ELL-L-De-Di-Rc
ELL-47-47-100-8
Where:
ELL = Elliptical transition down to inlet pipe
L = Length of bellmouth (or height)
De = Diameter of exhaust port (of the bellmouth)
Di = Diameter of the inlet port (of the bellmouth)
Rc = Radius of the corner
All dimensions are in 'mm'
I included some material in the throat or pipe section that is parallel with the carburetor throat because I want to be able to get at the screws that I'll be using to hold the bellmouth down. So the actual overall length is longer than the theoretical. This is ok because the bellmouth is really only bounded by the opening and the point where the outlet meets the intake tract of the pipe it is feeding.
Superhawk carburetor bellmouth base dimensions
Things to keep in mind:
* We're only trying to do better than the existing intake tract.
* The paper describes performance increase compared to a straight pipe with a simple ball radius
* The best we can hope for is a maximum of ~3.5% improvement over the straight pipe with simple ball radius (aka 3.5 hp on a 100hp machine)
* The existing design is OK but was selected for space constraints within the airbox including the breather piping, manufacturability, and need for extra fuel to cool the rear cylinder.
* The existing design is probably better than the baseline used for comparison in the paper. It has a taper (shallow) and a corner radius.
My expectation is ~2 hp but I'll have to do some tuning on the carb to get there.
You might check out the retainer that Felix Dellwood uses, It's simple and effective.It looks as though you could use it on any configuration of bellmouth.
Wow that does look good! Would take a lot less plastic to print and would be much faster because of no support needed.
The small one took almost 5 hours to print because of the support!
My print took 13+ hours and I can do only one at a time.
0.1mm layer height
0.8mm wall
40% infill
I sanded my print because the supports wouldn't release cleanly (almost at all). I had printed it inverted and used PETG filament. It has a 255C print temperature and is really pretty strong. The glass transition temperature is lower than for ABS. (ABS = 105C vs PETG = 88C) I still think I'll be ok.
The thing is huge but it follows the instructions for proportions that I found in the above mentioned paper.
De = 47mm
L = De
47mm
Di = 2.13 x De
100mm
Rc = .08 * Di
8mm
I set a circle as the top of the bellmouth profile and overlapped that with an ellipse that had the minor axis apex at zero height. It was surprisingly easy to draw up. I followed that with another version of the same thing that was 2.5mm outside and shorter than the first. This gave me a wall thickness at the top of the carburetor that matches the OD of the beginning of the taper. It sits just about perfect.
To secure the bellmouth, I'm intending to use a pair of 'L' shaped tabs on the side that will fit the bolt hole profile of the airbox. I'm not sure if I'll superglue it or print with it built in. I'm inclined to just glue it on as the tabs themselves won't fly around the airbox if they come loose. The bellmouth will just rattle some. A dab or two of RTV should take care of the effect of that failure mode. I do like the setup that Felix Dellwood is using but I'm not convinced it is necessary.
I might use you sketch there and make a mount attachment like Felix did.
I only printed at .2mm layers and its more than smooth enough.
Id like to change a few things to make it more printable for me. Without supports for one. I always try to design so I dont need them.
You're probably right about the print resolution. Supports for my design were only at the curve of the opening in the bellmouth. The print orientation was chosen for that reason.
I think I'll be stuck with making the stacks taller than the small one but I won't go any higher than the taller one. My reasoning is that I need room to get at the fasteners that secure it. I could probably go shorter if I just used RTV to hold it in place (I'm considering this). Alternatively, I could use studs and nuts to hold it down. It's been raining so I haven't had a chance to mock it up.
The other point is to determine what the tune should be. Swapping jets isn't terrible but it is a fair amount of work including all that fuel spill management. I've read a bunch about how to do this without a dyno and gas analyzer but I haven't set up my test procedure yet (blip test, throttle chop, reading the plugs, etc.). My goal is nice power (has enough of it stock), rideability, and decent fuel consumption. I'm not racing. I'm not looking for the last 1/10th. I'm a little bugged that I currently have to run non-oxy-fuel for it to feel good down low. We'll see what we end up with.
Full confession, I'm only doing this because I bought another Superhawk that needed to be put back together and it didn't come with the OEM velocity stacks. Penny wise!
I printed the one from thingiverse yesterday with the bell end up and the support was crazy. Never cleaned off well. I already have your sketch mocked up and im working on the hold down ring at the moment.
With mine you can print without support and have the bell end up for maximum quality.
Here is kinda a rough of what I have. It was taking your shape and adding Felix's hold down idea in two halfs. Im also trying to add under the bell so I can print without support and get a real nice round on top.
Id have to take my tank and airbox off again to see what all room I have in there for the design. Yours feels like it might be on the big side but im not sure until I can take more measurements.
You can trim the corner radius some and get the side angle even more vertical. The paper investigated a zero corner radius and a full ball. The results showed a very small hit due to the missing curvature.
If space becomes a problem, we're going to have to make some compromises. Trims and notches in the outer most portions of the bell are likely the best place to start.
I have an airbox I can use to mock up the carbs and bellmouths. I'll do that tonight.
So I did a bunch of measuring and mocking up. My conclusions are this:
1. The bottom of the flange that secures the bellmouth needs to be 33mm from the surface that meets the stopping ridge in the carburetor.
* Depth from stopping ridge to inside floor of airbox 20mm (almost dead nuts)
* Height of brass inserted bosses ~12.5mm (there seems to be a bit of variation)
* We want a little pressure holding the bellmouth down 0.5mm (or 0.020")
* The fasteners are 5mm
2. The geometry I selected fits rather well.
* All the breather piping and support structures have to be cut out (we need to put some kind of labyrinth feature into the piping opening - 3D printing?)
* The corner radius can/should be slightly trimmed to fit the front carburetor because of the breather trapezoid interferes. (I think what Floyd has is pretty good)
* The clearance below the air filter is about 12mm at the closest point. I think a 5mm reduction in height overall would be a good idea.
* Accessing the fasteners is rather cumbersome with the current geometry. Better with Floyd's tweak.
* The front and rear belmouth do not clash
In general it fits. Rear Carb. Notching was kind of aggressive and the breather piping had to be removed prior to installation. The stick is running across the mating surface of the airbox. The scale is resting on the stop ridge in the carb. This is photoshop magic but the scale is right
Straight off the printer without sanding or anything. Went with .3mm layers for speed at the moment. Fits together great but I havent tried it on the bike yet. If you want I can send you the STL files to try out yourself.
I forgot to post the second version of the bellmouth. I reduced the height and trimmed back the corner radius. I'll post my sketch dimensions when I get home. These pictures were on my phone.
Love it, but there is a minor point for correction. The extra fuel is not for cooling. The extra fuel is used because the air to the rear cylinder does not need to make a 90 turn and reverse direction like the front cylinder. Therefore, having better flow characteristics, it can use more fuel. To properly combat this, we would use stacks that are opposed, side by side and mirrored like on an Aprilia setup for one the V4's. In other words the trumpets would have to be contorted to be of equal length and bend. Another thought is the intakes that are available for BMW oil heads that are essentially tuned length pipes with a filter on the end. They do away with the air filter housing altogether and perform quite well. Looks good from my sofa.
I've reread my reply and considered deleting it because I don't want to come across as preachy or a big know it all. Please take the below in the spirit of friendly discussion and feel free to rebut my argument with your own theory.
For what it's worth, I was parroting what I'd read on the internet (an error free data repository) about the cooling effect of the fuel. That said, I still think it might be correct. The momentum of the incoming air on the SH air box is clearly toward the rear cylinder and would likely make for a straight shot and easier filling filling. However, the air first has to make a downward turn through the air filter toward the engine. At this point the only thing we've got going for us is the momentum of the air being pulled through the air box inlet providing some stuffing action for the overall intake tract. This pressure increase in the air box helps with engine volumetric efficiency and is why intake plenum design has been pushing toward ever larger volumes (there is a diminishing return/upper limit).
The differences of the two OEM velocity stacks is another item of interest. Here it gets a little more complicated. A shorter tract is better for high speed air intake and longer tracts better for low speed. The rear cylinder gets the longer OEM velocity stack. I suspect that the engineers were making a careful design choice here based on engine temperatures. The rear cylinder will have richer fueling at low(er) rpm. The coolant flow will be lower volume as well as the vehicle speed (direct correlation to air flow). Coolant flow rate has an upper limit on effect but it also has a lower limit. Air flow around the engine may seem inconsequential but in the end the air is the heat sink for the engine no matter what. The front cylinder gets blasted with cool air while in motion and some of that air (now warmed) gets to the rear cylinder but not nearly as much. My bike has had the fairings removed (I bought it as a crash recovery) so my rear cylinder cooling is probably better while my aerodynamics and appearance have suffered.
In the end, I think the whole discussion is academic. I want a bike that starts easily, pulls hard, and gets decent fuel efficiency. I'm not racing around the track looking for the last tenth of performance (I'm really only a decent street rider). My tune is going to be as good as I can get it with some effort and the tools at my disposal. For too long I've studied these kind of problems looking for the optimal solution and missed out on riding the damn thing (this and other bikes or cars or whatever). I am interested not so much in perfecting the intake performance of this obsolete, out of production motorcycle as much as getting it to perform robustly with parts that are cost effective to me.
Yes, the initial motivation for this was the fact that I didn't want to spend +$25 on replacement OEM stacks for the second SH I own (and am planning to flip). Natural curiosity and the fact that I can do this work on the couch has propelled it this far.
If you want to watch someone really get into the tuning of an engine/transmission setup watch 90GTVert on YouTube. He's freak'n amazing. I've come to prefer his voice at 2x speed though.
