Starter Relay Mounting

All,

When I mount my starter relay to the forward mounted battery tray per Van's drawings, the relay is very close to one of the engine mount tubes. I am sure that will rub. I am not sure why I have this problem. Perhaps I mounted my battery tray a little too low. My plan is to turn the relay upside down. (for reference, the top of the relay is where the mounting bracket attaches) However, I read in a past post that the orientation of the starter relay may be important. Is this true? Should I not turn it upside down?

Thanks,

I'm not familiar with the RV-8 mounting, but on the 7, Van's instructions show mounting the relay upside down. I've read in some other sources that the starter relay should be mounted upside down.

As I understand it, the internal part of the contactor that moves is normally held by a spring in the "up" position. This is assuming the contactor is mounted right-side up. When you energize the contactor solenoid, that internal part is pulled down and completes the circuit to the starter.

In flight, if you were pulling high positive g maneuvers, the g-forces could potentially overcome the spring force holding that part of the contactor up and the starter would engage. This could damage the starter and/or the flywheel. The assumption is that you'll pull more positive g's than negative g's, so mount the contactor upside down so that any positive g's are working to keep the contactor internals apart.

Now, that could be one of the throw-backs to the "days of old", but that's the way it's been explained to me.

If you can not invert the relay

apatti said:

All,

When I mount my starter relay to the forward mounted battery tray per Van's drawings, the relay is very close to one of the engine mount tubes. I am sure that will rub. I am not sure why I have this problem. Perhaps I mounted my battery tray a little too low. My plan is to turn the relay upside down. (for reference, the top of the relay is where the mounting bracket attaches) However, I read in a past post that the orientation of the starter relay may be important. Is this true? Should I not turn it upside down?

Thanks,

Click to expand...

Tony,
If for any reason you can not invert the relay, another option is to use (in my mind) a superior part. The older Ford style starter relay (with the large terminal studs sticking out each side) can be replaced with the newer style Ford starter relay (with the studs coming off the front).
This newer style relay will move the cable mounting points inward & is sturdier than the old style (1960s and 1970s) relay Vans recommends. The new style relay still mounts using the same nut plate mounting, as the old style. The heavy duty version (part # listed below) also contains a diode or resistor built into it.
This means that you don't have to add an external diode, as recommended by Bob Nuckolls. See

http://www.aeroelectric.com/Pictures/Contactors/s701-1.jpg

http://www.aeroelectric.com/articles/spikecatcher.pdf

The newer style starter relay (aka contactor) is available at any good auto parts store. It is Standard (that's the brand name) model SS598. This style of starter relay is in current use by Ford, and has been for over 20 years. A photo of it can be seen below.

http://www.aeroelectric.com/Pictures/Contactors/s702-1l.jpg

Just another option.

Charlie Kuss

Upside down?

D-Dubya said:

I'm not familiar with the RV-8 mounting, but on the 7, Van's instructions show mounting the relay upside down. I've read in some other sources that the starter relay should be mounted upside down.

Click to expand...

How do you define "upside down"? My RV-7 drawing illustrartes the orientation, but does not define it as upside down.

Dave Cole said:

How do you define "upside down"? My RV-7 drawing illustrartes the orientation, but does not define it as upside down.

Click to expand...

In my original post, I defined the top of the relay to be where the mounting bracket attaches. I don't know if this is standard or not. On OP-35 the relay is shown mounted right-side up (by my definition).

Charlie,
Thanks for the suggestion. If I can't figure out which way is up )), I'll look into the Ford relay.

Dave Cole said:

How do you define "upside down"? My RV-7 drawing illustrartes the orientation, but does not define it as upside down.

Click to expand...

Tony,

I've got a drawing showing a cutaway of a "typical" relay that I think will clarify what's up and what's down. But I don't want to get into any copyright issues on a post...I can send it to you in an e-mail if you'd like.

D-Dubya said:

Tony,

I've got a drawing showing a cutaway of a "typical" relay that I think will clarify what's up and what's down. But I don't want to get into any copyright issues on a post...I can send it to you in an e-mail if you'd like.

Click to expand...

Yes please and thanks! Send it to November Niner Seven AP (see sig at bottom) at Comsouth dot net.

Coming at ya

It's on its way. Let me know if it didn't come through for some reason.

D-Dubya said:

Tony,

I've got a drawing showing a cutaway of a "typical" relay that I think will clarify what's up and what's down. But I don't want to get into any copyright issues on a post...I can send it to you in an e-mail if you'd like.

Click to expand...

Ok, I know I am pulling this post off topic by asking this question, but, what does posting a picture of some item you are working on to an internet thread have to do with copyright laws? You are not trying to sell anything are you? The picture is for informational purposes not resale. Besides if you were worried about it simply post where the picture originated and give them credit for it. I fail to see where copyright would come in to play at all.

Mounted sideways?

I attended the EAA electrical workshop a while ago and remember being told that the relay should be mounted sideways. The reason for this is due the G forces applied to the part during maneuvers. If enough G is applied and the contact is installed right side up or upside down, then there is a greater chance of it being opened/closed during these maneuvers.

FYI - I'm not even close to doing this nor have I seen one installed so YM(and opinions)MV

Tony, you might make a scab bracket to raise it up a 1/2 inch or so. Best regards and still waiting on my Lyconosaur to arrive, Bill

Bill Phillips said:

Tony, you might make a scab bracket to raise it up a 1/2 inch or so. Best regards and still waiting on my Lyconosaur to arrive, Bill

Click to expand...

Well, I see you have cleaned up what you are calling your engine now!

That is true. Or, I could use some Proseal. (sorry folks, inside joke)

I just turned it over. Now the contactor has to fight the spring AND gravity in order to engage the starter. If I pull enough negative G's to engage this thing, I'll probably have more pressing things on my mind. I can't imagine there being a downside to the upside down (cute, huh) orientation. But I am not an expert on contactors.

If I remember right, there was disagreement on whether mounting it on its side was a good thing or not. This is based on reading previous posts on this subject here on VAF. Since the opinions are all over the place on this, it will be up to each of us make up our own mind. My conclusion is that probably any orientation is OK. However, because of my interference problem, I am going to mount it upside down and move on. YMMV.