I don't know the advantage of not putting it in, I was just confused as to why some people have it and others do not...
Aerhead mentioned a good reason a lot of people don't put it in (I'm not saying you should or shouldn't). If you have alternate air it bypasses the filter (obviously). If anything in that mechanism breaks (hinge, rivet, whatever), there's a good chance it can get sucked up into the engine.
I'm not sure that your statement is true about bypassing the filter. If I recall what I've seen from other's pictures, alternate air simply blocks the through-cowl intake scoop and pulls/redirects engine cooling air into the FAB.... The result is warmer air in the intake (as well as lower MP) which may be necessary for the curtailment of carb icing.
I'm not sure that your statement is true about bypassing the filter. If I recall what I've seen from other's pictures, alternate air simply blocks the through-cowl intake scoop and pulls/redirects engine cooling air into the FAB.... The result is warmer air in the intake (as well as lower MP) which may be necessary for the curtailment of carb icing.
I'm not sure that your statement is true about bypassing the filter. If I recall what I've seen from other's pictures, alternate air simply blocks the through-cowl intake scoop and pulls/redirects engine cooling air into the FAB.... The result is warmer air in the intake (as well as lower MP) which may be necessary for the curtailment of carb icing.
Fred, you're talking about the Carb Heat door on the stock (updraft) FAB - not the alternate air door, which draws air from the bottom of the FAB, through the center of the filter.
...Just thinking about your explanation regarding the "alternate air" setup...what's to keep whatever it is that's blocking the filter to not get sucked-up the alternate air door when opened?
Just thinking about your explanation regarding the "alternate air" setup...what's to keep whatever it is that's blocking the filter to not get sucked-up the alternate air door when opened?
Well, certainly that can't be right...it makes too much sense!
Thanks for explanation, Paul. "Learning has occurred!"
Just thinking about your explanation regarding the "alternate air" setup...what's to keep whatever it is that's blocking the filter to not get sucked-up the alternate air door when opened?
Hey, that looks pretty great. I'm working on the alternate air door for my horizontal induction engine right now, so this is very timely. I might try to copy some of the ideas above since I'm not thrilled with the factory design.
Just wondering, what prevents a loose screw from being sucked up into the engine with this design? Is there a layer of glass over the screw heads inside the airbox?
thanks,
mcb
Here are a couple of Pix of my alternate air slider which Lars previously referred to.
My device differs marginally from Lars' design in a number of small ways as follows:
1) I have used 1/8" rivets instead of screws and nuts.
2) I have rotated the mechanism on the FAB so that the control cable does not conflict with the aircraft nose leg assembly (A model).
3) I have placed the fasteners for the control cable adel clamp outside of the filter.
4) I have a bridge on the slider mechanism.
I'm not suggesting that any of these differences are improvements but they may be food for thought.
One thing is for sure. I'd rather have no alternate air at all than instal Van's terrible device. I can't believe they couldn't come up with a better design on their second attempt.
Well, one other thing: seeing yours makes me think about painting mine. Without, it's really ugly.
Lars, I'd be as comfortable with your effort as I would with mine. I think they're probably both bullet-proof.
It's nice to see that you used metal locknuts (I assume that in due course you'll torque mark them). I didn't use any nylock nuts FWF on my aircraft. Nor did I use any at the disc brakes.
Guys, can I offer a bit of philosophy?
Parts not on the airplane never give trouble.
One key goal is to eliminate the chance of (1) blocking the throttle bore with a loose large part or (2) ingesting a small part. I'd suggest the best way to do both is to simply eliminate the parts.
For example, do these designs really need the large aluminum sheet inside the bottom of the box? Why is it there, really? There is a chance it will crack and perhaps shed a section; the whole bottom of the box is moving like a drum head. Why not a few additional plies of glass fabric on the inside to thicken and stiffen the belly of the box?
Do the slider rails really need fasteners? Why not composite slides bonded to the outside of the box?
Guys, can I offer a bit of philosophy?
Parts not on the airplane never give trouble.
One key goal is to eliminate the chance of (1) blocking the throttle bore with a loose large part or (2) ingesting a small part. I'd suggest the best way to do both is to simply eliminate the parts.
For example, do these designs really need the large aluminum sheet inside the bottom of the box? Why is it there, really? There is a chance it will crack and perhaps shed a section; the whole bottom of the box is moving like a drum head. Why not a few additional plies of glass fabric on the inside to thicken and stiffen the belly of the box?
Do the slider rails really need fasteners? Why not composite slides bonded to the outside of the box?