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Vernatherm Types and Prices

DanH

Legacy Member
Mentor
Looking for a new vernatherm this AM....pricy little bugger. Noticed a few things.

The OEM and Superior (53E22144 and SL53E19600) vernatherms seem to be a product of Rostra Vernatherm:

http://www.vernatherm.com/

It's a core or capsule in a machined aluminum holder. Pull a retaining clip and the core slides out of the holder. We don't need a new holder to replace a bad core, but it looks like every parts source sells you one anyway, as an assembly.

Bashful fellow that I am, I rang up Rostra's engineer and asked him about the cores. He confirmed they are sold to other OEMs, but would not share the Rostra part number for the Lycoming application. My guess is you can buy the same core elsewhere (I dunno, Evenrude, Cummins, John Deere?) for a lot less than airplane prices. Basic outboard motor vernatherms are, for example, about $35. Anybody have a clue about an interchange?

Best price I've seen so fair for a Rostra-made Lycoming assembly is at Aero In Stock and Air Suppliers, both $248. Ouch!

ECI sells a "vernatherm" of their own design (or designed for them), part #AEL19600. I called ECI to confirm; it is not sourced from Rostra. Given that my OEM Rostra just died at 80-90 hours, that may be a Good Thing.

Different appearance is obvious:

http://www.eci.aero/pages/products_detail.aspx?in=529

Anybody have any field experience comments about the ECI unit?
 
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No O-360 support?

Hi Dan,

Looking at ECI's www site that you provided, there's no O-360 listed.


AEIO-360
HIO-360
HO-360
IO-360
IVO-360
LHIO-360
LIO-360
LO-360
LTO-360
TIO-360
TO-360
VO-360

I this an error?
 
Larry Vetterman is very adamant about removing the vernatherm altogether and replacing it with the oil cooler bypass plunger and a remotely-operated valve to manually regulate the oil temps. I have this setup on my rocket and am not yet flying.
 
Just a thought..........

How about talking to the folks that you got the engine from???

I would think this should be a warranty issue???
 
Dan, why not install an oil thermostat? The vernatherm is useless.
 
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Dan, why not install an oil thermostat? The vernatherm is useless.

Interesting comment, and nothing against a thermostat...but USELESS?!

I've had them in airplanes for decades - have never had one fail on me. I know that others have, of course - but since everything gets archived around here, that's a pretty extreme statement without a lot more data...
 
Really guys, I was hoping to focus on two areas:

Where can you buy the same Rostra core in the non-aviation world?

How good is the less overpriced non-Rostra ECI substitute?
 
ECI

Hey Dan,

I have an ECI IO360 in current 7. The vernatherm was check and it was reading 10 degrees low. I keep that in mind on my oil temp reading.

Did you give Rhonda a call to see what they can do? They might be able to exchange it.
 
Really guys, I was hoping to focus on two areas:

Where can you buy the same Rostra core in the non-aviation world?

How good is the less overpriced non-Rostra ECI substitute?

What are the specs as you know it on the Rostra device? I'm thinking oil pressure to which the device is subject and temperature range at which it opens. Probably the former is as least as important. I know nothing about outboard marine motors but a little bit about tractors and have access to lots more info. If you can obtain the core for $35 or less it might be worth buying one to mess with, if you find a promising candidate.
 
Different Approach

Dan,
Go back and ask for what they have and given them the specs. you need. Opening and closing temps, length and dia. They will come back with several items that match your specs and maybe you can narrow it down from there. We have to do this at work to get around the agreements between OEM and vender.
 
Ahhh, the joy of education and recreation....

Last night I started thinking about how it works. A few things had no apparent answer, and that sent me back to the hangar.

Today's lesson: do not remove the core from the holder before you boil it.

When removed from the holder you'll find a length of 1/4" dia rod inserted into a deep bore in the butt end of the core. What you don't know (and can't see) is that the end of the rod is against an internal piston. When the core is heated the internal piston pushes the rod, which pushes against the holder. That forces the entire core out of the holder against the pressure of the small diameter spring, which is stopped against the retainer clip in the slot.

Heating the core without the other parts just moves the internal piston. You won't see any length change on the outside. Unlike some illustrations out there, the rod in the nose of the core (with the nut) never moves. It is a stationary post upon which the seat cone can slide in the event oil pressure (because of a blocked cooler) overcomes the pressure of the large diameter spring.

When heated as an assembly, look for the length increase between the holder and the seat for the big pressure relief spring:

Vernatherm%20Drawing.jpg


When it cools, the small diameter spring forces the core to retract into the holder.

The measurements in the drawing are for my vernatherm....yours may be slightly different.

Careful measurement says the depth of the bore in the oil filter adapter into which the assembly is screwed meets the factory spec, 3.277" deep from the seal surface to the seat edge of the bypass passage. A plot of length change vs temperature says the cone should touch the seat (and block the bypass) at about 188F. That's about right; the holder is marked "85C", which would be 185F.

No crime in ignorance if you don't stay ignorant, right?

BTW, looks like the valve is in the Rostra 3255 series:

http://rostravernatherm.thomasnet.com/item/all-categories/oil-valves/pn-1011?#
 
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Well, I think so, but at this point I have my antenna up....wondering if I've missed something else. God is in the details.

For example, consider the pressure relief spring. As mentioned in the previous post, careful measurements says the cone should contact the seat at about 188F....but that doesn't mean it will seal. There is a pressure difference between the two sides of the bypass hole. The cooler pressure drop per the SW chart is 3.5 psi at 235F OT and 46 lbs/min. Add hoses, fittings, and a more realistic oil temp (more viscosity) and the total difference is probably 10 psi or more. The bypass seems to have an area about 0.25 sq in, so the vernatherm will actually need to extend far enough to compress the pressure relief spring to 2.5 lbs. Put another way, it won't actually seal at 188F. Full sealing will require some higher temperature.

I have the vernatherm in my hand right now, and I can compress the spring about 0.125" with just my thumb and forefinger. Don't know the actual spring rate, but I'll find out tonight. It's not real stiff:

Vernatherm%20Spring.jpg


Here's the thing. Recall that temperature vs length plot? Unloaded there's only 0.040" between 190F and 212F.
 
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Maybe you just have really strong fingers, eh. Seriously though, am I thinkng right that you could shim from the back to increase seat pressure as a test experiment? I know you know how little leakage it takes to affect oil temp. You're pretty confident with the seat fit?
 
No crime in ignorance if you don't stay ignorant, right?

If ignorance WAS a crime, I know a lot of people who would be serving consecutive life sentences!!!

Lots of good information in this thread. I checked my Vernatherm a few years ago and the length change was right, but I remember the spring being much stiffer. I was not able to pull it back like Dan did. Would that imply that once it reaches the seat it would seat tighter faster with less increase in temp?
 
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If ignorance WAS a crime, I know a lot of people who would be serving consecutive life sentences!!!

Lots of good information in this thread. I checked my Vernatherm a few years ago and the length change was right, but I remember the spring being much stiffer. I was not able to pull it back like Dan did. Would that imply that once it reaches the seat it would seat tighter faster with less increase in temp?

No, it would just have a higher bypass relief pressure.
 
Interesting comment, and nothing against a thermostat...but USELESS?!

I've had them in airplanes for decades - have never had one fail on me. I know that others have, of course - but since everything gets archived around here, that's a pretty extreme statement without a lot more data...

"Useless" may have been a poor choice of words on my part. I was needing to get somewhere and posted what I was thinking. ;)

I cannot figure out why more builder don't install oil thermostats. We have used them on Rotax 912's for a decade. Dan, you need to take a hard look at an oil thermostat. Toss that goofy vernathing, and design a modern cooling system.

http://thermostasis.com/
 
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I'll show my ignorance and sign up for my life sentence but isn't a Vernatherm just a particular brand and configuration of an oil thermostat?
 
Maybe you just have really strong fingers, eh.

Apparently yes ;)

I just came from the shop and measuring the spring rate. This pressure relief spring starts compressing at 14.75 lbs. That matches Lycoming statements about the relief pressure being 60-90 psi drop across the cooler circuit; a pressure relief valve with a port area of 0.248 sq in and a 14.75 lb spring would start to open at 59 psi. The spring rate is quite flat; it only rises to 17.75 lbs at 0.110 compression.

Anyway, the spring is not soft enough require any significant vernatherm extension past initial contact in order to overcome ordinary cooler circuit pressure drop.

I know you know how little leakage it takes to affect oil temp. You're pretty confident with the seat fit?

I'll take look up the bore. The cone has a nice even contact line all the way around.

I cannot figure out why more builder don't install oil thermostats. We have used them on Rotax 912's for a decade. http://thermostasis.com/

The referenced Rotax oil thermostat is a different vernatherm configuration in a different package. It does not include a pressure relief valve.
 
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Also confused

I thought a Vernatherm would do two things: (1) Control the oil Temperature by regulating the amount of oil flowing through the cooler, and (2) Acting as a Pressure Relief Valve in the case of a blocked oil cooler, such as might happen on a very cold day at startup.

Wondering why the anti-vernatherm comments? Reasons?:confused:
 
Well, I think so, but at this point I have my antenna up....wondering if I've missed something else. God is in the details.

For example, consider the pressure relief spring. As mentioned in the previous post, careful measurements says the cone should contact the seat at about 188F....but that doesn't mean it will seal. There is a pressure difference between the two sides of the bypass hole. The cooler pressure drop per the SW chart is 3.5 psi at 235F OT and 46 lbs/min. Add hoses, fittings, and a more realistic oil temp (more viscosity) and the total difference is probably 10 psi or more. The bypass seems to have an area about 0.25 sq in, so the vernatherm will actually need to extend far enough to compress the pressure relief spring to 2.5 lbs. Put another way, it won't actually seal at 188F. Full sealing will require some higher temperature.

I have the vernatherm in my hand right now, and I can compress the spring about 0.125" with just my thumb and forefinger. Don't know the actual spring rate, but I'll find out tonight. It's not real stiff:

x3d9fl.jpg


Here's the thing. Recall that temperature vs length plot? Unloaded there's only 0.040" between 190F and 212F.

Rostra site has a range of 20 to 100 lbs. for the bypass.

This spring is only a problem if your oil cooler is not cooling.

Does your oil warm up quick? Or does the oil get too hot? What made you want to test the Vernatherm?
 
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I thought a Vernatherm would do two things: (1) Control the oil Temperature by regulating the amount of oil flowing through the cooler, and (2) Acting as a Pressure Relief Valve in the case of a blocked oil cooler, such as might happen on a very cold day at startup.

Wondering why the anti-vernatherm comments? Reasons?:confused:

I'm not looking to start a vernatherm war, but it seems to me we could do better. Oil temps are critical for keeping an engine free of sludge and moisture, I would think we can all agree on that. There are dozens of threads about oil cooler doors, air duct flaps, duct tape over the oil cooler, etc., to keep oil temps at proper operating temps. The vernatherm never seems to be enough, or work right, or fails, or needs adjustment, ect, ect, ect. If it worked as advertized there would be no need for oil cooler doors, duct tape, ect.

It just seems to me to be an overlooked issue inwhich the brilliant engineering minds at VAF could overcome. We should be able to design an oil tempurature control system that works. A precision external oil thermostat seems to me to deserves a look anyway.

JMHO.
 
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I just came from the shop and measuring the spring rate. This pressure relief spring starts compressing at 14.75 lbs. That matches Lycoming statements about the relief pressure being 60-90 psi drop across the cooler circuit; a pressure relief valve with a port area of 0.248 sq in and a 14.75 lb spring would start to open at 59 psi. The spring rate is quite flat; it only rises to 17.75 lbs at 0.110 compression.

Very cool Dan, worthy. I don't know how you find the time & tenacity to get real numbers like you do.
 
I thought a Vernatherm would do two things: (1) Control the oil Temperature by regulating the amount of oil flowing through the cooler, and (2) Acting as a Pressure Relief Valve in the case of a blocked oil cooler, such as might happen on a very cold day at startup.

Correct on both Pete, although the pressure relief wouldn't come into play at start because the vernatherm is cold and thus the bypass port is fully open. You would taxi out, warm to 100F (or whatever you prefer), then launch. Sometime later when the oil reached ~180F and the vernatherm tried to close the bypass, a congealed cooler would result in enough pressure differential to force the cone off the seat by compressing the pressure relief spring.

There are dozens of threads about oil cooler doors, air duct flaps, duct tape over the oil cooler, etc., to keep oil temps at proper operating temps. The vernatherm never seems to be enough, or work right, or fails, or needs adjustment, ect, ect, ect.

Larry, the Thermostasis unit for the Rotax works on the same principles as the Lycoming system. When cold they allow oil flow to both the cooler and a cooler bypass. When hot they both block the bypass. They both use a vernatherm to do the job. Neither can force warming as neither can block the cooler.

That said, it does not appear to have a pressure relief valve, and if it doesn't a congealed cooler would result in oil starvation when the vernatherm closed the bypass. The same is true of a 912 without the Thermostasis unit, but it would happen at startup. With a stock 912 oil system, all oil must pass through the cooler to get to the pump.
 
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Just had a nice conversation with Ken Lionello, chief engineer at Rostra.

Ken says there is really only one significant failure mode, and eventually all vernatherms die from it.

Imagine a steel thimble filled with a hydrocarbon wax, then capped with a rubber diaphragm. When you warm the closed thimble, the wax expands and the diaphragm pushes outward against a little rubber plug. The plug pushes against the rod described in a previous post. That's the basic operating principle.

Ken says given enough heat cycles and calendar time, the rubber components get hard. Eventually the verntherm loses its ability to extend. He asked what Lycoming was specifying for a replacement interval; I told him "at overhaul".

He was kind enough to send a proprietary drawing because it lists some specifications. From the drawing and the conversation:

(1) Valve travel to be a minimum of 0.160" between 150F and 185F.
(2) Valve should close against seat between 183F and 187F.
(3) Pressure relief spring force is 15 to 20 lbs when the seat is pushed away from the nut a distance of 0.050". The result is a cracking pressure of 60-90 psi.
(4) Seat to sealing surface dimension (for us the bore depth in the oil filter adapter) is 3.280". The seal is assumed to be an aluminum crush washer of 0.0625" thickness. Reworking the seat may increase the 3.280 dimension and raise regulated oil temperature. A thinner crush washer will reduce regulated temperature but also reduce pressure relief clearance.

So, there we have it. Apparently there is nothing wrong with my vernatherm, but I've learned a lot about them. Hope you have too.
 
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Dan, mind telling us what, if anything, made you suspect your Vernatherm might be in need of replacement? Just reached what you thought would be a good replacement interval? Lower than expected oil temps indicating a possibly failed (open) Vernatherm? Looking for a little education myself...
 
Dan, mind telling us what, if anything, made you suspect your Vernatherm might be in need of replacement?

I've been seeing high oil temps lately (205-210) usually on the second leg after some hot time on the ground. I don't recall ever breaking 200 back in October when I started flying this crate. Perhaps OAT was generally lower and I was not paying attention, and I was flying with the largest of my three exit area panels for the first 6 hours. Whatever...it seemed sensible to check the vernatherm installation before proceeding with cooling experiments. As usual, one thing led to another.....

Full picture here:
http://www.vansairforce.com/community/showthread.php?t=68241
 
Thanks for the information, including the "how they work" information. I was most curious. Similar operating principle to an automotive coolant thermostat, as I expected. Roughly the same failure mode, too. In any case, nice to know a little more about the inner workings of these engines.
 
So, there we have it. Apparently there is nothing wrong with my vernatherm, but I've learned a lot about them. Hope you have too.

Good info Dan, as always.

So what is next if the vernatherm is working properly? Fly it and see or are you going to pursue other cooling measures?
 
So what is next if the vernatherm is working properly? Fly it and see or are you going to pursue other cooling measures?

After I give the vernatherm seat in the oil filter housing a good look it will be onward to other measures.
 
Thanks for the information, including the "how they work" information. I was most curious. Similar operating principle to an automotive coolant thermostat, as I expected. Roughly the same failure mode, too. In any case, nice to know a little more about the inner workings of these engines.

Maybe I don't understand what is meant above by "similar", but vernatherms could be considered the opposite principle to an automotive thermostat. The vernatherm is a normally open valve, which closes off as it warms up.

Vernatherm cold = flow through both the cooler and the internal bypass (in the engine). These two circuits are in parallel. Some sort of mysterious flow balance occurs between the two circuits when the oil is cold. This balance or lack thereof might explain why some engines' oil run so cool in the winter while others don't.

Vernatherm hot = closes the internal bypass circuit, making all flow go through the cooler. If cooler blocked, relief spring on the vernatherm allows oil to go through the internal bypass circuit anyway.

I think.
 
Maybe I don't understand what is meant above by "similar", but vernatherms could be considered the opposite principle to an automotive thermostat. The vernatherm is a normally open valve, which closes off as it warms up.

Vernatherm cold = flow through both the cooler and the internal bypass (in the engine). These two circuits are in parallel. Some sort of mysterious flow balance occurs between the two circuits when the oil is cold. This balance or lack thereof might explain why some engines' oil run so cool in the winter while others don't.

Vernatherm hot = closes the internal bypass circuit, making all flow go through the cooler. If cooler blocked, relief spring on the vernatherm allows oil to go through the internal bypass circuit anyway.

I think.

Alex- I was referring to the expanding wax pellet part of the function. An automotive thermostat has the same thing. The expansion of the wax pellet is used to opposite effect in a vernatherm, but the wax doesn't know that. And they fail the same way- rubber seal sticks, wax gets out, etc. Motion ceases to occur.

Actually I'm betting that vernatherms are manufactured more carefully- my luck with automotive thermostats has been abysmal. My wife always, always, pays attention to the water temp gauge/idiot light in any car she may be driving. There's a story behind that...
 
hey Dan H

hey Dan H
well i have seen some what the same thing and today i was trying some things to get the vernatherm to work sooner and it worked in climb
but then i was turning things on and off like lights, strobes and if i turn all on my oil temp goes to 300+ if i turn every thing of then from 215 it goes to 195 so tomorrow im doing a full test at alt
my old vernaterm was 0.02 longer than the new one
if you would like to call heres my number 602 697 4080
 
hey Dan H
well i have seen some what the same thing and today i was trying some things to get the vernatherm to work sooner and it worked in climb
but then i was turning things on and off like lights, strobes and if i turn all on my oil temp goes to 300+ if i turn every thing of then from 215 it goes to 195 so tomorrow im doing a full test at alt
my old vernaterm was 0.02 longer than the new one
if you would like to call heres my number 602 697 4080

I would look for a wiring problem.......... bad ground??
 
that was the first thing i looked at

I would continue looking at that. The electrical load shouldn't affect the engine operating temps much at all. If you are really seeing 300? oil, it would be burning/black in the engine, and coking everything up. Check for electrical issues again, and if there aren't any, I would NOT fly until that is resolved.
 
Lycoming Vernatherm

Does anyone out there know the difference between PN 53E22144A and just 53E22144 ? Just checking.

Thanks
 
hey Dan H
well i have seen some what the same thing and today i was trying some things to get the vernatherm to work sooner and it worked in climb
but then i was turning things on and off like lights, strobes and if i turn all on my oil temp goes to 300+ if i turn every thing of then from 215 it goes to 195 so tomorrow im doing a full test at alt
my old vernaterm was 0.02 longer than the new one
if you would like to call heres my number 602 697 4080

There is no way turning on electrical loads could cause actual high oil temps, you have an indication problem.
 
As a data point, I have a Mattituck 360 in my RV7. The AEL19600 Vernatherm worked great till recently. I was concerned about my engine as the oil temp seemed to be running away except at low power settings. Today I tested the ECI thermostatic controller. It only moved about .030" in boiling water. It has about 300hrs on it. Today I ordered the Superior unit from A/C Spruce to replace it.

Bob
 
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