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SDS FAB Mount Design

DavePlaneGrips

Well Known Member
I've run into a bit of a snafu fitting my FAB to my SDS intake and am hoping there might be better ideas out there. I made these standoffs to mount the FAB plate and a custom machined flange. I knew the bit of hose that came with the intake was too thick but figured there were thinner ones out there. The clearance between the standoffs and the TB OD is 1/16" but I haven't found any 2.5" ID hoses that thin, probably because it'd be too flimsy for most uses, but since I'm making my own flange (the gray one in the solidworks model) I figured I could make the gap between the TB and the new flange very small so it wouldn't be an issue (I can make them almost touch). Without turning down the standoffs more or cutting a chunk out of them I'd need a 2.5"ID x 1/16" thk hose, which I can't find...

This comes from my wanting to use a standard Vans FAB, the popular 90deg elbow and conical filter being overly restrictive from what I understand. Are there any examples of vertical intakes with the SDS TB out there? I didn't find any when I was searching. I'd appreciate any ideas/examples.

Studs are 5/8"dia. 4130N, formed 5/16-18 thread engine side.

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Solidworks model, gold TB is representative of SDS.

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I have been wondering how to attach the air box on our project------your idea is a great example of "out of the box" thinking...

Might have to steal it;)
 
Thanks Mike, glad it helps! If I can only figure out the connection...

Think I'll try scalloping out the standoffs, after noting the clocking of each standoff with washer+lockwasher installed, which will then make each one location specific... great.

That leaves less than D/4 wall on that side (0.044") because for some reason I drilled those 1" deep and 1/4-28 (think I could have got away with #10), but with 4130 and the thicker wall the rest of the way 'round it should be fine.



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Thin wall tube option

Make a custom tube out of glass and ultrablack. Consult Dan Hortons school of cool tricks here on VAF .
 
SCAT is available in 2.5". Wall thickness is 0.098 per the data sheet. You can probably get away with no clamp in that area, so if you can take another ~0.040 off the standoffs it will work.
 
Pretty good idea. Most folks were using the 2.5 inch hose provided and making new support brackets attached to the sump but this could be an easier solution.
 
After sleeping/thinking on this one I wonder how it would work to use coupling nuts to hold the TB in place, and run long bolts up to it from inside the FAB???

Use some tubing over the bolts to space the FAB as needed.

shopping
 
After sleeping/thinking on this one I wonder how it would work to use coupling nuts to hold the TB in place, and run long bolts up to it from inside the FAB???

Use some tubing over the bolts to space the FAB as needed.

shopping

I think I follow, that's what I started out with in my head. But I couldn't figure how to rigidly fix the FAB without having some solid standoffs come up and meet it.

Now I'm on to just machining a acetal (not Delrin) coupler.

Though if this were part of a kit I might expect tooling for a molded grommet would be worth it, just a thought :)

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So many acronyms

I'd love to follow along on this thread but the only acronyms in the original post I know are OD and ID (outer and inner diameter).

Is there a place to look these up?
 
acronyms

I'd love to follow along on this thread but the only acronyms in the original post I know are OD and ID (outer and inner diameter).

Is there a place to look these up?

FAB - Filtered Air Box. Van's sells it in different versions for different applications but there is not one specific to SDS so the OP is adapting to one with a blank top plate. It has the engine intake air filter inside.
SDS - Simple Digital Systems:
Electronic Fuel Injection (and ignition) at: http://www.sdsefi.com/aircraft.html
Coil Pack Ignition at: http://sdsefi.com/cpi2.htm
TB - Throttle Body, replaces carburetor because injectors are at intake runners.
4130N - 4130 steel alloy in the normalized heat treat condition.

The original poster, OP, is installing SDS EFI (and ignition).
 
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After sleeping/thinking on this one I wonder how it would work to use coupling nuts to hold the TB in place, and run long bolts up to it from inside the FAB???

Use some tubing over the bolts to space the FAB as needed.

That exact solution has worked well for me for 250+ hrs. Drilled allen-head bolts to safety wire below the FAB plate for retention. 5052 tubing spacers, though I now have some stainless tube I can use to replace if they wear.
 
That exact solution has worked well for me for 250+ hrs. Drilled allen-head bolts to safety wire below the FAB plate for retention. 5052 tubing spacers, though I now have some stainless tube I can use to replace if they wear.

That was my concern with an aluminum standoff, but it sounds like you don't have problems with cracking or wear. What are the dimensions of the tube you're using? If that works I'd rather go that route.
 
I didn't like the spacers with 1/4" bolts, had to be .020" wall thickness for the stock hose to fit, I might do that in steel but probably not aluminum. I already had these made so I figured I'd carry on.

Made the coupling and flange, fit is air tight.
 

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That was my concern with an aluminum standoff, but it sounds like you don't have problems with cracking or wear. What are the dimensions of the tube you're using? If that works I'd rather go that route.
Yours look fantastic, better than mine, which are admittedly just made up of spare tube I had laying about....I wish I had those kinds of skills. I just used regular -6 5052, originally bought from Spruce for some fuel line work. No cracking, but I had already made a thicker-than-stock top plate for the FAB (the actual thickness I don't recall). Looking back at my photos, I'd cut the tubes a washer-thickness shorter and add a regular washer to spread the load at the tube-to-plate interface.
 

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Mine's probably heavier than it needs to be, maybe I'll turn down the middle of the studs at some point but for now I'm ready to move on. Pretty new to machining so it took at least twice as long as it needed to lol.

I made a new FAB top plate too, 0.05" 4130.

Thanks for the kind words guys!
 
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