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Mounting Tachometer encoder

Bubblehead

Bubblehead

Well Known Member
I am installing a GRT EIS-4000 and bought one of Vans encoders to generate the RPM signal. The encoder shape is kind of wierd and I am not sure how to mount it solidly to anything.

Obviously it needs to be secured somehow. Can anyone supply some ideas or pictures? I want to mount it in the engine compartment.

Thanks,

John

Here's a picture of the device.

472370430_XYNnS-M.jpg
 
fab it

I made the mount/bracket from a piece of .062 AL stock approx 2" wide x 4" long. Drill a hole for the threaded boss (9/16"?). Drill another hole for the anti-rotation pin. Drill a third hole on the other end of the bracket for the adele clamp. Use an adele clamp (cushion clamp) to mount the sender bracket to an engine mount tube. I had to buy a thin nut from the local nut&bolt supply house so the tach cable nut would thread far enough on the sender.

Steve
 
Got it!

Steve,

I think you have it right! Sounds great and I will work on that tomorrow.

I'd love to see a picture but if none is available don't worry about it. The idea is simple enough that I can work it out.

For some reason I just didn't notice the anti-rotation lug or I would have thought of mounting that way.

Thanks,

John
 
John,

I helped a friend install his. We ended up using the 12" extension and then put an adel clamp around where that attached to the sending unit and another clamp on his engine mount. Worked great.
 
N941WR said:
John,

I helped a friend install his. We ended up using the 12" extension and then put an adel clamp around where that attached to the sending unit and another clamp on his engine mount. Worked great.
Click to expand...

Bill, I note that you and "Steve" on this thread recommend bolting the transducer to the engine mount.

If you go to the following thread on VansAirforce you will find my post #14 which has a photo that shows that the 12" extension cable must bend through almost 180 degrees if the transducer is fixed on the engine mount.

http://www.vansairforce.com/community/showthread.php?t=23828&page=2

I have reservations about the long term success of bending that cable through 180 degrees. I'm thinking that the tight bend MIGHT result in excessive friction and wear on the drive core and casing leading to premature failure. Presumably the attraction of mounting on the engine mount stems from the fact that it is quick and easy to achieve.

Do you have any knowledge of anyone who has had long term success with mounting the transducer on the engine mount. When you say that your friend's transducer on the engine mount "worked great" what do you mean. Do you mean that your friend's transducer system worked when he started the engine or that it worked well for a lengthy period of flight hours.

I'm thinking of being conservative and mounting the transducer to the firewall to reduce the cable bend to 90 degrees unless some-one has long term evidence that the 180 degree bend will hold up over time.

I'd appreciate your comment.
 
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Bob,

You make a good point about not bending 180 degrees. It could fail prematurely due to the stress. My friend has maybe 50 hours on his installation and it is still working fine. When and if it fails, I will report back.

FWIW, I've seen a few other installations that mounted the thing on the engine mount. I'm not saying this is good, just something we followed.
 
MINE IS FIREWALL mounted and is dirt simple............... I will get a pic on Wed and post it here..............
 
mounting

I mounted mine with a medium size tie wrap to an aluminum angle inside the fuselage. Three years later and 500 plus hours. no problems.

Steve
 
Steve Barnes said:
I mounted mine with a medium size tie wrap to an aluminum angle inside the fuselage. Three years later and 500 plus hours. no problems.

Steve
Click to expand...

Well Steve, I hadn't given much serious thought to taking the 12" extension cable straight back through the firewall. But in thinking about the fact that you have 500 hours of success with this technique it may make logical sense. After all, the standard mechancial tacho drives that everyone has been using for years has to come back through the firewall.

I'd be reasonably sure that the drive core in a mechanical tacho cable would not like very much bend at all. Even 90 degrees may be too much. If you stop to think of what is happening to the drive core on a bent cable as it rotates through 360 degrees (one side of the core has to undergo a cycle of compression and then a cycle of tension for each rotation) then that must be quite gruesome on a core spinning continuously at such high speeds.

Anyone out there got any serious hours up with a 90 degree cable firewall mounted transducer.
 
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BEND IN CABLE

Bob, That's exactly the reason I ran as straight as I could. I wanted avoid unnecessary stress, and keep the unit cool. Steve
 
Captain Avgas said:
Anyone out there got any serious hours up with a 90 degree cable firewall mounted transducer.
Click to expand...

Odometer cables on millions of cars make a 90* turn after they leave the transmission on the way to the dash. Would it be better in line? YEP! Is the 90* an issue? Nope! The ones in Pipers etc. need to make "S" turns from point "A" to point "B" and they do just fine.

I think a 180* might be pushing it a bit. You might need to change it during an eng. OH.
 
In my installation there's insufficient room between the engine and firewall to allow the tach transducer to be mounted. Since the aircraft had previously had a mechanical tach I just re-installed the original tach drive cable (which hadn't yet been yanked out of its firewall feedthrough), and then installed the transducer to structure in the cockpit using ty-wraps. The cable has been in place since Day 1, 450 hours ago. It's always had two 90 degree bends in it, one behind the engine transitioning to vertical, and one before going through the firewall. It then had a nice gentle S-bend to get to the tach in the panel, probably a total of another 45 degrees of bend. This has proven reliable for quite some time now so it's not something I'd worry about.
 
mechanical to electrical

The EIS has an electrical wire for a tach signal off of the mag P-lead which is the way I did it on the one I'm working on. Small panel, no room for a seperate tachometer.
However if using a seperate tach then the transducer and mechanical cable are needed but why not use a mechanical tach and not have to deal with a funky mount? It needs a cable either way. With the transducer you can put it in the engine compartment and eliminate a firewall penetration which is nice.
Just my .02
Phil
AME at Large
 
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