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Prop Governor Spring Is Too Powerful

Joe

Well Known Member
In my RV-8A project I find that the spring in the prop governor is so powerful that it puts the prop into the full high RPM setting unless I set excessive throttle friction (one setting affects all three levers on the quadrant). At any reasonable setting of the throttle friction, the prop control won't stay put; it moves forward.

The governor is a Hartzel S-1-0 bought from Van's and
the throttle quadrant is the "deluxe" model (there's nothing deluxe about it) from the accessory catalog.

I'm not interested in converting to a separate control for the prop governor. And I think I understand the reason for the spring (high RPM in case of cable breakage).

So what does that leave me for an acceptable method of dealing with this? Is it permissible to "unwind" the torsion spring mounted around the cable-connect arm of the governor to effect less force on the cable?

Thanks,
Joe

 
You are dealing with an experimental airplane. You can do anything you want with the spring. I had a similar issue with the "deluxe" quadrant. The single friction lock would bind one control before it added a bit of friction to another. I ended up using a separate vernier control for both prop and mixture controls. (I know, you don't want to do that. I must ask, why not?) Most modern aerobatic aircraft use this set-up. I'll never go back!

paneltilt2.jpg
 
...I ended up using a separate vernier control for both prop and mixture controls. (I know, you don't want to do that. I must ask, why not?) Most modern aerobatic aircraft use this set-up. I'll never go back....

+1 on the entire post. Do what you want with the spring... And the vernier on the prop and mixture is the only way to dial in RPM and LOP temps... And they stay that way no matter how loose the throttle lever is.
 
Thanks for both of your replies. Sure, I can do what I want with the spring but I'm looking for "accepted methods"; I'm loathe to capriciously toss out a safety feature.

OTOH, the push-pull cable is highly unlikely to break, so maybe removing the spring really is the answer. After all, there are no springs on the throttle and mixture controls.

This is yet another part of the RV-8A build that falls into the category of "if I had known then what I know now ...". :-(

--
Joe
 
I've come to the same point. With a 3 lever quadrant, I need too much friction to keep the prop lever steady. I also spend way too much time fine tuning the power. Time to change to vernier prop and mixture.
 
Thanks for both of your replies. Sure, I can do what I want with the spring but I'm looking for "accepted methods"; I'm loathe to capriciously toss out a safety feature.

OTOH, the push-pull cable is highly unlikely to break, so maybe removing the spring really is the answer. After all, there are no springs on the throttle and mixture controls.

This is yet another part of the RV-8A build that falls into the category of "if I had known then what I know now ...". :-(

--
Joe

Joe,

I would never bypass a safety feature without giving it a great deal of thought. Look at it this way. If your prop control cable breaks and there is no spring to drive the governor to fine pitch what are you left with? At worse a prop in coarse pitch. Not feathered or in reverse pitch! So what do you do in that worse case? Land without incident and fix the cable. You will have ample power at coarse pitch to do a normal landing. Maybe even a go-around!
 
Joe,

Did you contact the governor manufacturer? I know my PCU-5000x governor is available with different torsion spring configurations. Maybe they can provide a weaker spring.
 
Last edited:
Joe,
I had a similar concern with my Hartzell governor during installation. I had the following email exchange with Hartzell support:

I asked:

I am installing the throttle quadrant in my RV-8, and I noticed that the spring force from the governor to return to 'fine' position is faily large, and will require a lot of friction locking on the quadrant to hold a prop setting.
Is this spring force reduced when the engine is running due to oil pressure?



Les Doud, from Hartzell replied: (a member on these forums BTW)
Yes, the spring force is reduced with the engine running but not from oil pressure; the flyweight reaction is what reduces the spring force.

If the spring force is still considered unacceptable after you start flying, let us know and we should be able to provide a spring with lower force.


I have been flying for a year and a bit now, and I find the tension on the quadrant acceptable (ie: smooth to operate, and it doesn't drift) with the stock spring.
 
Yes, the spring force is reduced with the engine running but not from oil pressure; the flyweight reaction is what reduces the spring force.

If the spring force is still considered unacceptable after you start flying, let us know and we should be able to provide a spring with lower force.

I have been flying for a year and a bit now, and I find the tension on the quadrant acceptable (ie: smooth to operate, and it doesn't drift) with the stock spring.

Thank you, Chris; this is the best news yet! I had not considered that the net force of the spring would be different under operating conditions.

I had taken Sparky's suggestion and called Hartzell. The nice lady in tech support had actually heard of this situation before but said they didn't have any other springs. They did have some different lever arms (at $27.50 apiece :mad:) that I could experiment with. F'getaboutit!

But for the archives and for anyone who cares, here are the Hartzell lever arm part numbers and their hole-to-hole distances:
  • 102309 1.3 inches (came with the governor)
  • 102551 1.5 inches
  • 102368 1.637 inches
  • 103568 holes at 1.3, 1.713, and 2.125 inches)
Later I spoke with Gus at Van's and he acknowledged the problem. Some RV-10 builders (who occasionally also use the quadrant) have been running into the same issue. Gus suggested adding a tension spring to counter some of the force of the Hartzell torsion spring. One end of the new spring could easily be anchored on the cable attach bracket but the spring rate and length would still require calculation and testing.

"Unwinding" the tension spring is not a very good idea; nearly all of the force probably comes from the last turn. It would have to be "unwound" a fraction of a turn which would necessitate a new attach tab.

So plan A is to do like Chris (I will re-evaluate after flying) and plan B is to contact Les Dowd about a new spring if needed.

--
Joe
 
Simple Fix!!!!!

....You could add a small helper spring to cancel off part of the other spring and adjust it to what ever it takes to keep everything happy. Simple and not costly and very easily removed if you desire. :D
 
I give up

I've come to the same point. With a 3 lever quadrant, I need too much friction to keep the prop lever steady. I also spend way too much time fine tuning the power. Time to change to vernier prop and mixture.

I too have been assimilated and am ready to become a vernier control user :-(

After flying Phase I with my "deluxe" throttle quadrant, I can honestly report that it sucks in spite of my best efforts with a "helper spring".

AdditionalPropGovernorSpring.jpg


The helper spring pictured above was too strong and I have since cut it down to about half so it no longer rubs on the silicone M.P. line. It's still far from satisfactory and I'm ready to try a vernier on at least the prop control cable.

Can anyone who has successfully installed a vernier for the prop control on a small bracket below the instrument panel give me a pointer to a suitable cable length or better yet, a part number?

Thanks,
Joe
 
Can anyone who has successfully installed a vernier for the prop control on a small bracket below the instrument panel give me a pointer to a suitable cable length or better yet, a part number?

Thanks,
Joe

Joe,

I used a 4-foot cable from Aircraft Spruce. This worked fine with the cable mounted on the gear tower as shown.

20130301114241u.jpg
 
When converting the -8 over to the vernier controls I found that the ACS controls had far more travel available than the arms on the governor and mixture could use. Consequently, the knob moved only about halfway in its travel. The fix was to fabricate longer arms and now the knob strokes full travel and delivers a much finer adjustment.

Just something to keep an eye on.
 
Joe, Dont give up! Let me see if I can get you some direct help from the Hartzell governor team. Ill get back to you on this.
 
Just a note about the quadrant itself. I noticed during my build that the friction knob was applying pressure to the side of quadrant, resulting in poor and uneven friction control. I placed an aluminum tubing spacer underneath the friction knob. This allowed the pressure to go through the side plate hole and directly to the control arm spacers. Look into this before going into major changes.

Bird
 
... I placed an aluminum tubing spacer underneath the friction knob. This allowed the pressure to go through the side plate hole and directly to the control arm spacers ...Bird

Good to know. But the friction knob already goes through the side plate hole and bears on the mechanism so I'm not following you. Maybe your quadrant is different. I checked your build log but nothing showed up. Can you post a picture of this?

... I found that the ACS controls had far more travel available than the arms on the governor and mixture could use. Consequently, the knob moved only about halfway in its travel. The fix was to fabricate longer arms and now the knob strokes full travel and delivers a much finer adjustment.

That's good to know too. I've already had to swap out the throttle lever arm; guess I should not have expected the prop and mixture controls to be different :-( If I went the vernier route, I'd probably go with one of Vans' cables (used on the side-by-side models) and I'd like to think it would be a good fit.

Meanwhile, Kahuna/Mike Stewart tells me via email that he'll ask Hartzell about the new spring they're working on so I'm not going to install a vernier just yet. He also says he has seen success using a cut-down standard spring although I'm going to wait to hear from Hartzell.

--
Joe
 
Update on the prop governor spring

... Kahuna/Mike Stewart tells me via email that he'll ask Hartzell about the new spring they're working on ...

Forum member Les Doud of Hartzell Propeller wrote me yesterday with an offer to participate in a service eval (along with Team Aerodynamix) of a new lighter prop governor spring they're working on. YES! That's the right solution and I'm grateful for the chance to participate as an early adopter.

I'll report back when I've received the spring and had time to install and fly with it.

Thank you, Hartzell and Kahuna.
 
Thank you, Hartzell and Kahuna.

You are welcome. We noticed this issue a few months back. The return spring on the gov was pretty strong. THere were design reasons for this. This would ONLY affect those with quadrants that run with little friction lock or no friction lock at all. A vernier would not even notice this. But for our team, that runs with no friction on the quadrants since we are constantly moving the throttle to do what we do, well this was immediately apparent. So Hartzell went off to engineer a lighter return spring.
While they were doing that, we cut our springs down to make them lighter. Works.
A great example of a supplier working with end users, listening, and updating their products to support us RV'ers. The thanks goes to Hartzell.
 
I'm reviving this thread to see if Hartzell ever came up with anything to help the high governor spring force when using a Vans deluxe quadrant. With first flights this weekend we found quadrant friction had to be very high to keep governor setting in place. I would prefer almost no friction so fine tuning throttle setting is easier. Not ready to convert to a vernier just yet or adding a "helper" spring. Anything new on this?

I'll post more info and hopefully video on first flights separately - the 8 is awesome!!
 
I spoke with Hartzell on this. They haven't come up with a lighter spring. They suggested a longer control arm but I don't see what difference this would make other than change the throw on the quadrant lever. They did say they are aware of the issue and would like to do something for the RV folk with quadrants. It would involve some modification to the governor and would I like to beta test it free of charge. I told them I was in Phase 1 and not up for it at the moment. If anyone is interested they could give Hartzell a call.

I also emailed Vans about this today so should hear if they have anything to add soon.

For now I have some interference on the rear throttle push rod and need to lube the quadrant pivot and boelube the slot where the quadrant levers go thru. This should make the throttle smoother and make it work better with the governor spring as it is.

Another thought is to take the governor spring off or unhook it and leave it up to the quadrant to have 100% control. I guess the only thing is if the cable ever breaks or disconnects the prop would either go fine or coarse pitch or stay where it was - I'm not sure. Any one tried this? Comments?
 
Vans got back to me - They are aware that the Hartzell gov spring pressure is a problem with their quadrant but don't have a solution. The MT gov works better in this application because it has a lighter spring.
 
I spoke with Hartzell on this. They haven't come up with a lighter spring.

There is a lighter spring. We have installed a number of them, but I do not know if it is a publicly available one or perhaps we are just a test bed for them. Ill reach out to them and find out what the status is on these and report back.
 
There is a lighter spring. We have installed a number of them, but I do not know if it is a publicly available one or perhaps we are just a test bed for them. Ill reach out to them and find out what the status is on these and report back.

That would be good, because the word I heard around here was that Hartzell was approached about providing a different spring for RV installations and they said no.
This is also what has squashed any thoughts about working up a quadrant kit for the RV-14.
 
Going to the longer arm on the governor should help some. Can anyone tell what length governor arm worked best with the Vans quadrant?
 
Teflon washers

I put teflon washers from McMaster on both sides of the throttle and mixture levers. If I recall, I had to up the length of the bolts that hold the quadrant together by one number. If the slight extra width messes with your mounting scheme, you could shorten the spacers by the thickness of the teflon washers and use the same bolts it came with.

With the friction lever cranked down enough to hold the prop securely, the other levers still move easily. In 90 hours of flight, I haven't messed with the friction lock once. The force to move the throttle and mixture feels just right to me and they are very smooth. The action on the prop doesn't seem wrong at all - stiff enough to stay put, but easy to adjust the RPM.

Ed Holyoke
 
Ed

Good suggestion, I will order the washers. Do you have the part number for them? I would still like to increase the length of the arm on the prop governor as my prop control now only uses about half of it?s available travel.
 
McMaster doesn't seem to have teflon washers. I probably used these UHMW:
Packs of 25
In stock
$7.75 per pack of 25
95649A229

Worth trying, lubricant filled nylon washers:
In stock
$2.33 per pack of 5
91545A240

Ed Holyoke
 
Shortly after I posted a comment to this thread on 4/2/18 I was contacted by Hartzell and asked If I would like to beta test a new spring on my Hartzell prop governor. I returned my governor to them and they installed the new spring and sent me a longer arm for the unit also. I have now flown a few hours with it and I am very pleased. With very little friction set on the controls they all stay in place. The longer arm had three holes in it and the middle one gives me full travel with the prop lever. My aircraft is an RV-8 IO-360-M1B with the rear mounted governor with the standard 3 lever control quadrant. Prior to this change My prop lever only moved about half travel and required an excessive friction setting to lock it in place. I believe they will accept more aircraft in the beta test. You must return the governor to them for installation of the spring. They will not install the longer arm but will provide it for you to install which is very easy. Because this is a beta you will have to provide them with periodic reports on how it is performing. Contact [email protected].
 
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