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If it's not one thing, it's another: Mixture lever interference

grayforge

grayforge

Well Known Member
I'm setting up an ECI engine with their forward cold air sump (angled up 7 degrees), Precision Silverhawk FI and a B&C starter...

My initial attempt at getting the mixture lever set up failed with the mixture arm (offset version) hitting the back of the starter.

For the 2nd try, I cut the end the arm off and re-drilled further in along the arm. Again, no joy. The bolt head hit the starter.

Some options:
  1. File a relief notch in the corner of the alternator where the bolt head touches. The interference is only 1/16 or so.
  2. Swap on an arm with a 1 1/4" offset, but that's a long ways out, plus, the rod end bearing would need to be on the outside, making for quite an odd angle between bellcrank and mixture arm.
  3. Replace the B&C starter with an inline Plane Power one. But I like the well known reliability of the B&C and have seen specs showing the inline NL starter has a lower RPM than the standard configurations.
  4. Rotate the mixture arm to the lower position, ditch the bellcrank and route the mixture cable below the sump. The question here is: what sort of bracket to use to hold the cable? Maybe something attached with the bolts holding the intake manifold to the sump? Adel clamps on the intake tubes? Custom cable length?

Anyone solve this combo?

Thanks!
Russ

Shortened mixture arm still hitting starter:
DSC00416.JPG
 
grayforge said:
I'm setting up an ECI engine with their forward cold air sump (angled up 7 degrees), Precision Silverhawk FI and a B&C starter...

My initial attempt at getting the mixture lever set up failed with the mixture arm (offset version) hitting the back of the starter.

For the 2nd try, I cut the end the arm off and re-drilled further in along the arm. Again, no joy. The bolt head hit the starter.

Some options:
  1. File a relief notch in the corner of the alternator where the bolt head touches. The interference is only 1/16 or so.
  2. Swap on an arm with a 1 1/4" offset, but that's a long ways out, plus, the rod end bearing would need to be on the outside, making for quite an odd angle between bellcrank and mixture arm.
  3. Replace the B&C starter with an inline Plane Power one. But I like the well known reliability of the B&C and have seen specs showing the inline NL starter has a lower RPM than the standard configurations.
  4. Rotate the mixture arm to the lower position, ditch the bellcrank and route the mixture cable below the sump. The question here is: what sort of bracket to use to hold the cable? Maybe something attached with the bolts holding the intake manifold to the sump? Adel clamps on the intake tubes? Custom cable length?

Anyone solve this combo?

Thanks!
Russ

Shortened mixture arm still hitting starter:
DSC00416.JPG
Click to expand...

Remove some of the bolt head?
 
Mixture

I had the same problem. The solution for me was to reverse the arm so that instead of pointing upward it pointed down. I then made my own bracket for the mixture cable. That seems to work and eliminated the Vans toggle arm linkage. Hope this might be useful. PM if you'd like pics.....
 
What about the possibility of flipping the bolt and putting one of those small steel locknuts on. That should easily give you 1/16".
 
Bill, I responded to a post of yours on another thread... your inbox is full. :)

Jesse, Hmmm... that's an interesting idea. Though I'm a bit leery of replacing a castle nut with a locknut.
 
The RV-10 plans call for these on all if the controls. That's all I use. The rod end bearing should be the only thing moving, not the bolt. Just like all of the control surfaces using locknuts when there is a rod end bearing. You shouldn't use a nyloc in the engine compartment, but a steel locknut is fine.
 
I found a smaller diameter, all metal locknut (1/4" socket). The bolt shaft, nut and washer now barely graze the the starter. If I filed away a bit of the housing, I could get 1/16 to 3/32 clearance. Enough?

The throttle cable bracket that's attached to the sump-to-case studs adds enough thickness that the studs barely reach the top of the nuts (vs 1 thread showing). I may look into thinner nuts.
 
Any clearance is better than none. If you push on he throttle cable hard, would it still clear? If so, the. I would call that acceptable.

On those studs, you could probably get longer ones. As long as the nuts have lock washers under them, going with a thinner nut will only weaken the system. The rule of thumb is 1.5-3 threads past the nut, but that is especially for locking style nuts. I would rather get longer studs than use thinner nuts in this case. Full thread contact gives full strength. Maybe use a thin flat washer with the lock washer to get a thread showing. Also, those internal teeth lock washers are single use only, so you would need to replace it if you pull that nut.
 
Hmm... pulling the sump and installing longer studs sounds like a big job.

Now that I think about it, the bracket is powder coated. Removing the powder coat and adding a thin coat of primer might give me a bit more thread purchase.

Or I could trim the tabs on the bracket enough to nestle into the valleys around the studs.
 
Look at a bolt with a round head and internal hex. I forget what they are called. The overall diameter of the head is quite a bit smaller than a standard bolt. They are typically an alloy and are quite strong.

Larry
 
Russ---This is somewhat interesting. Not from a hose standpoint, but from a consumer --or potential consumer.
I'm wondering if any of the other engine guys are having fit issues with accessories like this? I know that Barrett uses alot of cold sump applications. I know from a hose building standpoint that its really hard to think of every scenario and accessory, but in your case, an engine case, a starter, a sump, a servo, all have rather finite mountings. There has to be an economical solution.
Tom
 
shorter rod eend bearing?

I don't know if these are acceptable solutions, but what about:
1. can you get a rod end bearing that is shorter in total length? Or,
2. a longer bolt in the bracket that would allow the rod end bearing to be lower?
 
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Bill Dicus said:
I had the same problem. The solution for me was to reverse the arm so that instead of pointing upward it pointed down. I then made my own bracket for the mixture cable. That seems to work and eliminated the Vans toggle arm linkage. Hope this might be useful. PM if you'd like pics.....
Click to expand...

This is exactly what I did. No clearance issues and it gets rid of that heavy, sloppy Rube Goldberg intermediate linkage thing.
 
Bill: Nice find! They have good strength specs. I just added some of those to my weekend Spruce order along with the pan head screws. :)

blueflyer: Good thoughts. I did try shortening the rod end bearing assembly by trimming off about 1/4" of the male threads. However, I found that this causes the rod end bearing to form an extreme angle with the servo arm at full rich, so I didn't actually use the full shortness that I created with trimming. One thing I did do which helped get full range on the rich side was to grind a small relief notch in the bellcrank bracket. See photo below.

Walt: Moving the servo arm aft a tooth would make the rod end bearing hit the bracket even sooner. Going forward a tooth would cause a more extreme angle between the rod end bearing and mixture arm.

Michael: I was considering that option. Do you have any photos of the bracket setup you made?

Thanks!
Russ

Relief notch ground into mixture bracket to allow full rich with mixture arm clocked in reasonable position:
DSC00426.JPG
 
TS Flightlines said:
Russ---This is somewhat interesting. Not from a hose standpoint, but from a consumer --or potential consumer.
I'm wondering if any of the other engine guys are having fit issues with accessories like this? I know that Barrett uses alot of cold sump applications. I know from a hose building standpoint that its really hard to think of every scenario and accessory, but in your case, an engine case, a starter, a sump, a servo, all have rather finite mountings. There has to be an economical solution.
Tom
Click to expand...

Yep, it is frustrating that the various build options, while common, often don't work with supplied hardware and plans. It seems they are designed for a standard lycoming with non cold air sump. As soon as you start changing things... I wish the ECI (and Superior) cold air sumps put the throttle body flange in exactly the same spot as the lycoming horizontal sump does. Would save a lot of builders a lot of time.

I'm not relishing the work needed on the snorkel. :-(

Tom, this sounds like a good opportunity for a fabrication service. :)
 
One pleasant thing from yesterday's work was the throttle linkage. While the standard orientation of the throttle cable bracket didn't work, reversing it so the flange was aft and doing some minor bending to get the proper aim, worked like a charm! I didn't even need the spacer Vans specifies in the plans.

Throttle cable bracket reversed
DSC00428.JPG


Geometry works out without a spacer
DSC00429.JPG
 
grayforge said:
...Michael: I was considering that option. Do you have any photos of the bracket setup you made?...
Click to expand...

No pictures handy, but the concept is very similar to what you have for the throttle. On the left side of my oil pan, down low is a boss with two holes. I made a simple bracket to hold the bulkhead nuts on the cable. One difference I did though, is extend the length of the mixture arm so that I could take full advantage of the longer throw offered by the ACS 1760 vernier control. Makes for very fine adjustments. (Higher resolution).
 
Russ---we face the same issues with hose packages. You would be amazed how many different combinations of FWF hoses I've done for a 'similar' install --say a IO 360, vertical sump, with a flow transducer. It would be SOOOOOOO nice to have a engine case (not necessarily with the internals), and different accessories on a factory mount, with a firewall, so you can actually work out alot of the details beforehand. Same goes for the cabins---say spar forward, especially on the RV10's.

My plan ( of many) is to build a full size cabin mockup to do just that. RV10, RV7/9, and RV8. (Probably doing the 7/9 cabin first since thats the plane I'm building). The FWF would be able to connect just like on a real plane, so visualize a full size cabin from spar to the crank flange, and see how everything interfaces with each other. Problem is its expensive! Engine cases, sumps, servos, oil cooler, exhaust, etc---the list get huge in a big hurry.
In the case of the RV10 cabin, different selector valves, boost pumps, and filters, yield several different varieties of hose lengths and routings.

If some of our great vendors would participate, that would be AWESOME!

So---I can feel for the engine manufacturers. Coming up with install applications that work for our purposes is difficult, and frankly part of the 'experimental' nature of our business. They (we) to assume that the builder has some fabrication and 'engineering' skills to solve some of the issues that arise. What gets me is that components installed by the manufacturer that sometimes have operational issues. But we are guys and gals with brains---we can figure it out.
Tom
 
Hmmm... my Precision throttle body has the mixture control high on the throttle body when on the left side while the throttle is low on the throttle body.

So the throttle is easy to get to from a low mounted cable, but the mixture will be tougher, especially since I have the ECI sump with the cold air inlet canted up 7 degrees. I'll take a look at how feasible this is with the ECI sump.

Toobuilder said:
No pictures handy, but the concept is very similar to what you have for the throttle. On the left side of my oil pan, down low is a boss with two holes. I made a simple bracket to hold the bulkhead nuts on the cable. One difference I did though, is extend the length of the mixture arm so that I could take full advantage of the longer throw offered by the ACS 1760 vernier control. Makes for very fine adjustments. (Higher resolution).
Click to expand...
 
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Well Bill & Michael, I took your comments to heart. You're right that the standard Vans bellcrank solution is Rube Goldbergesque. More complexity, weight and slop.

So I grabbed some soft aluminum sheet for prototyping and fabricated a bracket that solves this problem. I've included a drawing in case anyone wants a head start building this design. It turned out quite well. Decent distance from exhaust, pretty straight shot at the mixture arm.

Just ordered some .050 4130 for a permanent bracket.

The prototype bracket installed
DSC00443.JPG


Drawing of the final design. The 3/4" distance between the .25 holes is more critical than their positioning distances. Some tweaking may be required. Oh, and the large hole is 7/16.
DSC00446.JPG


And the 'stuff' I get to remove. :)
DSC00447.JPG
 
Looks great. Easiest half pound you ever lost, I'll bet. One thing to watch out for now is the inlet. I had some clearance issues with the "smooth cowl snorkel", but that had something to do with the longer arm I used. That was rectified easily by molding in a dent for clearance.
 
What about the arm itself?

I'm not there yet myself so I haven't even examined my own mixture arm. However, it strikes me that this is the other variable you have that you can work with.

If you heated it, could you change the geometry enough to give you the clearance you need?
 
I hadn't thought of that, but possible. I'd be a little leery of heating & bending such a critical item, but that's just me.
 
You probably have this figured out already. I believe The Van's stock bracket reverses the throw?. If so, if you go with a straight bracket you have to reverse the mixture arm. I assume you have done that (tough for me to find buried in all of the posts).
If not, Precision can reverse the mixture control operation. I do not believe it can be done in the field.
Also, the inlet can be swapped, side to side, and the outlet can be swapped front to back.

Between all of these combinations, intake spacers, arm types, etc... and some creative bracket work, you can resolve most issues regardless of engine and sump type.

Looks like you have it handled nicely.
 
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Yep, the control arm is re-oriented from the top to the bottom where it needs to be in order to be reached by the low mounted cable. This kills 2 birds with one stone: positions it where it can be reached and un-reverses the operation. :)
 
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