What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Honda 1.8L on RV6A Now Flying!

Ok, same as your earlier post so my analysis is valid I believe.

I appreciate you looking at that again. Since those moments of "stumble" lasted only about a second, and only 2 times, and I cannot recreate it, I am fine with proceeding testing.

My (main) challenge now is getting the right pitch on the prop, and probably put a cooler on the gearbox.

As I get up to altitude, anything about 5-6k altitude the engine creeps up as the turbo holds 30". rough numbers are that the engine is at about 4100rom at 30" of MAP MSL. But at 7k altitude it is 5000rpm at 30"map. While the engine is happy at that rpm, the gearbox is not. The gearbox hold 180F until I get past about 4300rpm (depending on OAT).

Plus I have a real nasty oil leak somewhere and I cant figure it out.

....but the plane is a blast to fly and the engine runs great. From my humble opinion I like how the turbo comes on strong at about 3800rpm. It sees to be great holding 30'-35" MAP. in fact it feels like there is a lot more power after that, but I have not ever pushed it past 37" and I don't plan to and don't need to. I just to get more prop pitch and an oil cooler on the gearbox.

Sorry for repeating myself. Just trying to explain the situation.

Thanks to all the support!!!
 
There is lots more power there and a great temptation to use it but usually at some cost-fuel flow, engine longevity etc. Like you say, performs well on what you have now. It's smart to keep the MAP down for the time being.

The fixed pitch prop will be a bit of a compromise with a geared turbo engine as you're seeing now. It gets worse the higher you go as hp doesn't drop off with altitude. You'll probably have to coarsen pitch some more once you get all the gear fairings on.

Glad it's going well so far and you're having fun. :)
 
Charlie –

I follow your progress daily and I’m very happy to see you flying and sorting out systems.

If I may ask a question… I know it’s early in the program but I’m trying to determine how your Honda 1.8 turbo compares to a Lycoming in similar RV-6A airplane. I think you said your engine is lighter weight. When things settle down perhaps you can share climb rate, cruise speed, fuel burn, etc.

I’m very interested in following your project. Wish you were closer and within flying distance.

Best Regards…
 
Jim,

Good to hear from you.

The real difficult aspect of comparing my set up with a Lycoming is not with the engine, but as you know I am quite limited right now with the gearbox and unfaired large tires, proper, etc.

In other words, if by chance we could find another RV6A using a Warp drive prop, with unfaired gear legs and 6.00 x 6 for main tires, and a radiator in a belly scoop, then yes, we could make a apples to apples comparison of the power output of both engines (in a relative sense), but of course that is not going to happen, and I get it.

The process for me is really proof of concept and not for outright speed. Id love for someone else to take that as the focus on their project.

Ill keep posting as long I think folks are interested in the process. While I rarely hear from folks, I see the number of "views" shows me there is quite a few lurkers who for what ever reason have not wanted or felt the need to make a comment. Which is absolutely fine.
 
Last edited:
New prop pitch

UPDATE:

I increased pitch on the 3 bladed 72" warp drive prop from 20 degrees to 21.2 degrees. (not 22.1 as previously posted).

It is a better fit for me. I did not discern any reduction in climb, but I did pick up about 5mph. I was only up for about 0.6 hours and did not do the required 3 leg course for a valid speed number. But, that said, I think I am seeing 130mph at 25" at 5k altitude. I typically climb out at 600fpm at 90mph.

I have not done any valid fuel burn calcs.

The challenge right now is that my PSRU box will get above 180F if I run the engine more than about 4200rpm. At MSL that is about 31" of MAP. At about 5k feet, it is at or below 25".

QUESTION: What pitch are folks typicall using for a prop pitch? Google says that 22degrees is about 80-82 inches. Does anyone know if this is valid?

Thanks.
 
Last edited:
180F doesn't sound like it's too warm for the gearbox. I wonder what the limiting design factor is - oil lube temp, bearings, gears, seals?

My RV-12 with Rotax 912 sees 200F oil temps and sometimes as high as 230F in hot weather climb. The engine oil is shared with the gearbox so I would assume the gearbox runs pretty hot. There is no air blast directed at the gearbox. The oil used is Mobil 1 Racing 4T Full Synthetic Motorcycle Oil 10W-40 which is specially formulated for engines that share oil with gear drives.
 
180F doesn't sound like it's too warm for the gearbox. I wonder what the limiting design factor is - oil lube temp, bearings, gears, seals?

My RV-12 with Rotax 912 sees 200F oil temps and sometimes as high as 230F in hot weather climb. The engine oil is shared with the gearbox so I would assume the gearbox runs pretty hot. There is no air blast directed at the gearbox. The oil used is Mobil 1 Racing 4T Full Synthetic Motorcycle Oil 10W-40 which is specially formulated for engines that share oil with gear drives.

Jim,

I have heard similar comments. I think RPM is an equally important here. What is the max RPM that you use, including max cruise? Does Rotax publish a max temp for operations?

I still will respect my gearbox manufacturer recommendations. They want to update my gearbox so I will send it to them real soon. If I see similar temps after it is updated, then I will work with them on the numbers and potentially add an oil cooler. Until then I am really limited on taking advantage of the actual performance of this set up.
 
In addition to the discussion about speed and performance. I thought it worth commenting that this set up uses a 2.33:1 ratio on the gearbox.

So 4000rpm is about 1700 RPM and 4500rpm is about 1900rpm. So my speed numbers combined with everything else is consistent. And of course should not be compared with other engines running props at 2400 - 2600 RPM.

I am very happy with the set up and as Ross said there are several things that can be implemented to increase performance, but for now, I will be focusing on building time in a safe and measured approach. Improvements will be coming in time.

I still would be curious about the (fixed) pitch of the props that "regular" RV's typically use.......
 
I still would be curious about the (fixed) pitch of the props that "regular" RV's typically use.......

I can't imagine that a typical FP RV prop, designed to run at 2500-2700 would do very well on an engine that will max out at 1900 RPM.
 
Jim,

I have heard similar comments. I think RPM is an equally important here. What is the max RPM that you use, including max cruise? Does Rotax publish a max temp for operations?

I still will respect my gearbox manufacturer recommendations. They want to update my gearbox so I will send it to them real soon. If I see similar temps after it is updated, then I will work with them on the numbers and potentially add an oil cooler. Until then I am really limited on taking advantage of the actual performance of this set up.

So, the 912 runs at 5500 RPM cruise which is engine redline. It is designed to operate at this speed and produces near 100HP. Gear ratio is 2.43:1 which is a "hunting" ratio to spread wear evenly. Rotax doesn't measure temp on the gearbox.
 
UPDATE:

QUESTION: What pitch are folks typicall using for a prop pitch? Google says that 22degrees is about 80-82 inches. Does anyone know if this is valid?

Thanks.

Most propeller pitch measurements are taken at about 3/4 radius. So, for your prop at 22 deg

circumference = pi * 3/4 * 72 = 146.8 inches
pitch = 146.8 * tan( 22) = 59 inches

If you're measuring your pitch angle somewhere else, adjust the numbers accordingly
 
UPDATE:

I increased pitch on the 3 bladed 72" warp drive prop from 20 degrees to 21.2 degrees. (not 22.1 as previously posted).

QUESTION: What pitch are folks typically using for a prop pitch? Google says that 22degrees is about 80-82 inches. Does anyone know if this is valid?

Thanks.

Van's recommended FP pitch for 160hp lyc. is 80 inches and 2600 rpm.
 
My gear ratio is 2.2 and I run a 76 IVO in-flight adjustable from 115 to 145 inches pitch and similar engine rpms to you. I run about 125 inches pitch for TO and climb at about 2050 prop rpm and 135-145 in cruise at same rpm, depending on power setting and altitude.

I run out of pitch above 10,000 feet and 30 inches MAP in cruise- If I want to go faster, engine/prop rpm will be higher.

As an extreme at 15,500 ft./ 35 inches, prop rpm full coarse was 2500, 182 KTAS.
 
Guys,,,,,,

Thank you!!!. This definitely confirms what my research is telling me. Which is that my speed is very closely matched to my ptich and prop RPM.

It gives me something to consider in the future, which is that my set up needs more prop to take advantage of what is available.

There are options.

1) More pitch. I will be increase pitch incrementally under the advisement of the manufacturer. ....
2) Another prop.....(I am currenly utilizing a SAE1 bolt circle so options are limited.
3)Possibly try to get a lower ratio for gearbox to increase prop speed.

On a side note, I am struggling with a pesky oil leak. Driving me nuts.

Oh well. Life is good.
 
I can't imagine that a typical FP RV prop, designed to run at 2500-2700 would do very well on an engine that will max out at 1900 RPM.

I agree, and would never consider it for my current set up. The information just helps as I consider several options for the future.
 
Charlie, when the gearbox is sent back, any chance to get an SAE 2 flange installed or a dual pattern 1 and 2 installed? This would open up some other prop possibilities in the future for you.
 
Charlie, when the gearbox is sent back, any chance to get an SAE 2 flange installed or a dual pattern 1 and 2 installed? This would open up some other prop possibilities in the future for you.

I am using a saber extension, and yes, Sam can make one for me with an SAE2 pattern. But if I can get the gearbox to keep the temps down at higher (4800-5000rpm) and add one more degree of pitch (22*) I think I can get the full potential of this set up (albeit fixed pitch) and Ill be fine.

I have a 1.25" blast tube of air on the box too, but a larger one would be helpful.

Ill be down until I get the gearbox back. That will give me time add ducting to the intercooler and replace the aluminum brake lines with coppernickel.
 
Last edited:
Good news. I got an all clear from Viking Aircraft Engines. They said the gearbox is fine. It just gets a bit warmer in my set up than in others.

I have a 1.5" airblast tube on the gearbox but they suggest something larger. I will be enlarging or adding a second airblast tube, and may be a old fashion oil cooler too if needed.

I hate having missed 7-8 beautiful weather days but I felt it was best to be cautions and have the gearbox looked at.

After that oil leak in the valve cover I have oil all over the firewall and down in the belly scoop to clean out. How fun!

I have been studying a lot on prop pitch. Comparing degrees of pitch vs inches of pitch.
l
I have a propeller calculator that is very helpful. You can find it at www.godolloairport.hu

I have been running 21.2 degrees pitch as measured at the tip of my 72" 3 bladed warp drive prop. I can run it at 33"map and 4500 rpm during climb out but due to the gearbox temp getting up past 180F I have to slow it down to 4100rpm so my "top end" speed is really an unknown for now. I am going to push it harder while the gearbox oil is under 180 as soon as I get back to flying. I am also going to increase pitch to 22.0 degrees pitch to see how that will work out. The "book" says that 22.0 degrees should give me 145mph at 2050 Prop RPM. The MAP will vary at altitude. About 32" at MSL and probably 25" at 6000ft. Just raw guesses at this point.

If I can keep the box cool under 185F I would love to run it at 6000ft at 3" to see if I could cruse at say 155mph. That would be pretty good considering I have unfaired gear legs and large tires and a radiator under the belly.....
 
Ross,


Is the marcotte a 2 or 3 gear set up? Do you run regular gear oil and if so do you monitor the temp? Is the oil cooled in any way?
 
The Marcotte is a 2 gear setup with the pinion inside the ring shaped output gear.

I have a 2 inch blast tube directed at the case plus a fair spinner gap which floods the whole case with air. Oil temps never exceed 140F.

No external cooler and I run 80/90 synthetic gear oil.

It's never been touched internally in 18 years and over 400 hours. Backlash at the prop tip is the same as when it was new.

You can see the gear layout here: http://www.sdsefi.com/air14.html

I have 3 of these gearboxes, one in the RV-6A and 2 spares (one was for the RV-10).
 
The Marcotte is a 2 gear setup with the pinion inside the ring shaped output gear.

I have a 2 inch blast tube directed at the case plus a fair spinner gap which floods the whole case with air. Oil temps never exceed 140F.

No external cooler and I run 80/90 synthetic gear oil.

It's never been touched internally in 18 years and over 400 hours. Backlash at the prop tip is the same as when it was new.

You can see the gear layout here: http://www.sdsefi.com/air14.html

I have 3 of these gearboxes, one in the RV-6A and 2 spares (one was for the RV-10).

The numbers speak for themselves, a great testament for Marcotte gearboxes. I wish they had the shaft offset (8.6") I needed when I was in market to make a purchase.
 
Impossible to have that much offset with this design so it doesn't lend itself to inline engines very well.

They're not the lightest drive around (crazy thick castings on the bell housing adapter) but one of the most robust. Russell Sherwood uses the same one on his 230hp EG33 with many SARL wins, really beating on it.
 
Viking said my gearbox looked good and I will get it back tomorrow, which considering I am in Washington State and they are in Florida, is a remarkable quick turn around. It was sent on last Wednesday and back 8 days later.

I just need to work on some solutions for cooling it better. I do like the box, it is light weight and compact, and it does have the shaft offset needed for using an inline engine. I have one 1.5" blast tube on the bottom main drive gear. I think I can add another one to the top gear area fairly easily. If that does get me where I want to be I will add an oil cooler reservoir to try to act as a heat sink - but without the complexity and weight of a pump. Last will be a full oil cooler with a pump and dedicated blast air to the cooler.

As usual, I will try these solutions incrementally to see how each performs.
 
Last edited:
Update

I got the gearbox back from Viking. They gave it a clean bill of health. All in all a pretty quick turn around - about 8 days, from Washington to Florida and back.

I took advantage of the down time to install a heatshield under the top cowling. I bend 0.40 aluminum sheet in the shape of a hand and epoxied them to the bottom of the cowl so I could rivet a sheet of 0.25 aluminum sheet to the standoffs. This provided about a 1.4" air gap between the shield and the cowl. Cheap, easy and very effective. Notice the stubby drill bit. Very important when drilling in to these stand offs so not to protrude in to and through the top cowl!

Plus I routed some 2/5" ducting to supply blast air to the intercooler. This is clearly very rough (crude) as far as streamline airflow goes but as far as cooling function it will be very effective. Notice that I also used the same kind of standoffs to attach the ducting band clamp. Great way to put support where you need it the most.

I also increased prop pitch to 22 degrees. I did a taxi test and could quickly see this gave me 32" of MAP at 4100 RPM on the ground with full brakes applied. This is a noticeable increase in MAP.

I hope to fly tomorrow to get some data.
 

Attachments

  • top cowl heat shield standoffs 600px.jpg
    top cowl heat shield standoffs 600px.jpg
    101.7 KB · Views: 212
  • top cowl heat shield 600px.jpg
    top cowl heat shield 600px.jpg
    93.3 KB · Views: 221
  • intercooler ducting.jpg
    intercooler ducting.jpg
    104.9 KB · Views: 223
Last edited:
Charlie -

Does Viking say what is the limiting factor for gearbox temperature? Gears, Lube, Seals, etc. I would think gearbox could operate at engine oil temps.

It seems that 200F would be reasonable...
 
Last edited:
Charlie -

Does Viking say what is the limiting factor for gearbox temperature? Gears, Lube, Seals, etc. I would think gearbox could operate at engine oil temps.

It seems that 200F would be reasonable...

I talked with Jan. He said that he does not see and you should not see over 180F on the gearbox even if it is running at 5000rpm.

Unfortunately, I cannot let it run past 4100 or it goes to 190-195F.

I added a 1.5" blast tube. It did not seem to make a lot of difference. May be a drop of 5F. He suggests a 2.0" or larger blast tube.

it will be easier (compared to enlarging the 1.5") to add a second blast tube via my nacelle inlet, so I will be doing that. But to be honest, I don't think it will drop the temps enough. Hence I plan to add an oil cooler. Two thoughts run through my mind. 1) There is only 8 oz of oil in the gearbox. While that may be good for many other folks, it does not seem to be enough for my set up. 2) adding an oil cooler not only is likely to reduce the oil temp, it also adds volume to the oil available to the box. Just my uneducated thought. Ill try the oil cooler without a pump first, and if it is not cooled enough Ill add a pump. Just trying to keep it simple.

The results of the 4100 RPM limit is mostl significant at higher altitudes. at MSL I am able to run 32" map at 4100rpm. But the RPM on the engine creep up rather dramatically as I gain in altitude. Ideally of course I would have a constant speed prop. Or at least be able to run the engine at peak TQ which is 4800. With the 2.33 ratio, I am only turning 1760rpm on the prop so you can see how much this is hurting top end performance. I think I am down below 25"map at 6000ft. The engine would be very happy at 32".....wish I could utilize this!

Since my climb is still close to 1000ft I may try 23" of ptich on the prop, but not until I get a few other sqawks worked out. Like my pesky valve cover leak.
 
Last edited:
8 oz of oil is not very much. My wife loves to bake – she says that’s 1 cup. By comparison, the Boeing B-17 had 37 gallons of oil per engine. The USAAF had a large strategic oil reserve to feed big radial engines that leaked and burned oil to beat the band.

Add’l oil for the gearbox, especially run through a cooling radiator, should do the trick…
 
The Marcotte M-300 (a much larger gearbox) runs about 14-16 oz of gear oil. Overfilling them increases oil temps noticeably.

A small cooler will be more effective than the blast tube. If you can situate the inlets and outlets to facilitate oil flow from the gear movement, that would simplify the system.

On the prop front, the fixed pitch prop is a big performance hold back on a turbo engine as I predicted before you flew. If your get enough pitch for high altitude cruise, TO and climb with suffer quite a bit unless you can sock the boost to it down there.
 
I talked with Jan. He said that he does not see and you should not see over 180F on the gearbox even if it is running at 5000rpm.

Published Viking service bulletin says 170 max.

Unfortunately, I cannot let it run past 4100 or it goes to 190-195F.

Perhaps, rather than cooling, it would be best to focus on why it is running hot. The increased temperature suggests increased stress.

Is the long propshaft extension typical for installations with this gearbox? It has the potential to greatly increase bearing load.

Perhaps you might attach three or more thermistors to the case, adjacent to each bearing set or individual bearing, in an attempt to localize the heat source.
 
Published Viking service bulletin says 170 max.



Perhaps, rather than cooling, it would be best to focus on why it is running hot. The increased temperature suggests increased stress.

Is the long propshaft extension typical for installations with this gearbox? It has the potential to greatly increase bearing load.

Perhaps you might attach three or more thermistors to the case, adjacent to each bearing set or individual bearing, in an attempt to localize the heat source.

It would be good to find out why it's getting so hot but I'd be very surprised if it's bearing related. It would take tremendously high loadings to generate significant heat here and the bearings would probably have shown significant distress already if that was the case- assuming the bearings are properly selected and of good quality (not cheap offshore brands I hope).

Typically a lot more heat is generated at the gear set where the profile/ mesh isn't good or surface finish is poor.

Support shaft deflection can cause edge loading on gears and roller elements.
 
Last edited:
I would be good to find out why it's getting so hot but I'd be very surprised if it's bearing related....Typically a lot more heat is generated at the gear set ...Support shaft deflection can cause edge loading on gears and roller elements.

All true enough. Question is, why would Charlie's box be different from the norm? So, I ask about the prop extension and consider bearing load, which translates directly to case deflection.

Whatever the source, better to find/treat the cause, rather than the symptom.
 
All true enough. Question is, why would Charlie's box be different from the norm? So, I ask about the prop extension and consider bearing load, which translates directly to case deflection.

Whatever the source, better to find/treat the cause, rather than the symptom.

Are we sure others are not having the issue given the past repression of information? Anyone else flying Viking GBs here on VAF who'd care to comment on temps?
 
My Viking gearbox temps track the coolant temp, typically +2 deg over coolant temps after warmup. "Normal" appears to be 180 deg at 7,000 ft in flight at 5400 rpm. Hot days can see temps in the 195 degree range. I would expect that to be normal as there is no thermal break between the engine and gearbox and I do not have have any specific cooling air ducts directed at the gear box to add cooling.

My gearbox maintenance manual lists the normal gearbox operating temperature range as 180-220 degrees and states "The gearbox temperature should always be equal to or lower than the coolant temperature." I use 210 as the caution setting setpoint and 220 as the redline on the Dynon. I am running AMSOIL 75-90W synthetic gear oil and change it every 50 hours. I disassembled the gearbox at about 25 hours to upgrade the drive plate on the input shaft and did not note any wear.

Not sure how you can expect to have a 50-60 deg temperature differential (170 GB Max vs 220-225 max coolant temp) without a separate gearbox oil cooler and/or lots of cooling air over the gearbox.

John Salak
RV-12 N896HS
 
1.8 honda

Charlie, glad to hear your flying ! I am still way behind as far as finishing my
701 Zenith. Your observations with gearbox still have me leary, will most likely
Go with airtrykes unit like I had in RV4 Tom Hankamp
 
I appreciate all the comments and questions.

Ill do my best to touch on these......

Most of the Viking Gearboxes, appear (to me) to be used on zenith aircraft. It is good to get the data from John who uses a Viking set up in his RV12. I am surprised to hear that his manual states 190-220f for an operating range for his gearbox. I did not get a manual with my box, and in fairness, that is probably because I did not buy a complete FWF set up from Viking, I bought just the gearbox.

I know Viking has several (at least 3) different models... the one used on the 110, the standard 130 and the Heavy Duty version. I am using the Heavy Duty version.

John, is your gearbox the standard version? I suspect it is. My HD box is listed to use 8pz of 75-145 synthetic gear oil.

It is possible some folks do not even use temp sensors on their boxes.

Other than Jan's comments that I should not see higher than 180F I really do not have actual user information other than What John Salak just posted.

As far as Dan H comments, I think the thermistor idea is interesting. I cannot say that even if I had that data, we could make much of a comparative analysis of it, but it is an interesting thought.

I also cannot say that I am seeing much higher temps that other similar applications see, other than Vikings comments. It would be fascinating to hear from other end users.

It is interesting to hear Dan comments about the 170F limit verses Johns 180-220f range. This may be because of difference in gearbox models. I cannot say. And yes, Dan, it is the 3 gear box.

I always knew a fixed pitch would be a compromise, and of course I am fine with that, I just wished the gearbox was not limiting me on using at least a 4800 rpm range when I want to use it.

Ross, yes, I use 32MAP mostly on take off. I will probably start using 35" at least for some testing. (I have suffered from a valve cover oil leak lately so I have been keeping my boost fairly low until that is resolved. I think I have the cause and solution in place and hope to do more testing on it tomorrow). I suspect my engine would be capable of 40" but I am not comfortable going there, at least not yet. I only say this because 35"map seems to have a lot of throttle left and there does not seem to be any reduction or resistance at 35" setting.

I usually see 185F on the hot side of the coolant system and about 150F on the cold side of the radiator. But its been in 30F OAT lately. I can get it to go to 195 if I do a steep climb for over 15 min. of course those temps would be warmer if it was summer weather....

I am going to pause here and go back and re-read some post, I don't want to miss anyone's questions.
 
Last edited:
Charlie, glad to hear your flying ! I am still way behind as far as finishing my
701 Zenith. Your observations with gearbox still have me leary, will most likely
Go with airtrykes unit like I had in RV4 Tom Hankamp

Tom, This may sound weird coming from me but I am not unhappy with the Viking gearbox. I am not a mechanical engineer, but it looks to be very well made and I think Viking is seeing a lot of success with this box. I think as soon and I can cool it, it will be a great set up.

I think I remember Airtrykes would not be happy camper with 160-180HP on that unit, but I may be wrong.......
 
Last edited:
John, is your gearbox the standard version? I suspect it is. My HD box is listed to use 8pz of 75-145 synthetic gear oil.

The sight glass is 5oz. As you know, the 8 oz requirement came after Jon Fay experienced a failure of the upper bearing set, same box:

http://www.zenith.aero/forum/topics...hours?id=2606393:Topic:695488&page=1#comments

Other than Jan's comments that I should not see higher than 180F I really do not have actual user information other than What John Salak just posted.

Fay is reporting temperatures generally lower than yours. Looks like he records his flight data.

I gather different boxes have different temperature sensor locations. The three gear HD seems to have the temp sensor at the very top, not submerged in oil, but apparently subject to splatter from the upper gear.

Be safe Charlie. There be dragons.
 
My reference data is for the two-gear 110 gearbox with two GB oil temp sensors above the drive gear, so the oil temp is for oil slung off the gears. My information from Viking is the standard three-gear version is the two-gear with an idler gear added to reverse the prop rotation. The drive gear/bearings and prop gear/bearings are supposed to be interchangeable between the two. As to the HD version, I can only speculate on wider gears and larger bearings for the additional loads vs the standard.

As you can see in the attached engine run chart (3 hr flight) the coolant temp, oil temp, and gearbox temp all track the flight profile for climb, cruise, and decent. I would be concerned if the "normal" maximum temp is 170 and you are seeing higher numbers. The higher temps are a function of either less cooling air over the gearbox or higher than "normal" friction loads on the bearing and gears.

Have you considered that your engine is producing more power than the Viking engine ratings that are used to produce the 170 deg reference temperature? A blast tube to the gearbox may help in determining the source of the higher temperatures. You may want to try AMSOIL SEVERE GEAR 75W-140 lube to see if that might help lower the temperature on the friction side.

https://flic.kr/p/2k5vkdx

John Salak
RV012 N896HS
 

Attachments

  • Engine Run Chart 20200905.jpg
    Engine Run Chart 20200905.jpg
    429.4 KB · Views: 203
Last edited:
Take care in comparing to a two-gear box.

Each gear mesh will double the heat generated. You can figure that the heat is about 6% of power being conveyed (3% per mesh). With the right lubricant and IF gears, properly sized gears that could be as low as 3% (1.5% per).

A flooded gear box will increase friction in churning loss too. Many gear boxes have a sling collectors to gather oil, capture, and allow it to drain back to a bearing. It's a first on the design list solution for lubrication. It sounds like this box could use that. 99% bearing failure is due to lack of lube.

This gear box should not need EP additives (boundary lubrication, low speed/high torque), but synthetics have shown lower friction and wear (and temp).

These are rough numbers, but by example, A working Cat D11 final drive temperature dropped around 50-75F with IF gears, a substantial drop.

IF = isotropic finish
 
Next steps for me are to retest the temp sensor to make sure it is at least real close to being accurate. The only way for me to do this - without pulling the panel out is to remove the sensor and stick it in boiling water. I tried the laser temp ga but I just did not feel good about it. Ill probably do both.

I also have an email in to Jan at Viking asking him for his thoughts on routing the oil cooler lines. I have not heard back from him yet.

I cruised to day at 4100rpm. I saw 190F in level flight which was about 26"map. I did a 100fpm climb and the temp rose up to 200F. That may be more about air flow than "stress".
 
Just a spitball. A higher viscosity oil could cause higher temps. Viking seems to recommend 75w90. “Heavy Duty” 75w145 oil might be too viscous for the recommended operating temps and is meant to be used in higher temps operating conditions.
 
so i have to ask what is probably dumb question but why is the max 180 deg.? the faucet on my kitchen sink can take higher temps. does it have anything to do with the max temp some additives can operate in without breaking down?
 
The AMSOIL 75W-90 gear oil I am using in my gearbox has a temperature limit of 250 F according the manufacturer, which is +30 above my redline temp for the gearbox. The radial seals appear to be the limiting factor, a SKF Nitrile rubber (NBR) seal size (60x70x7) on the prop gear shaft is rated for 100C max (212F), although other vendor NBRs appear to be rated up to 120C (248 F) max. I did see a 102C (216F) peak on an extended high-power ground run of the engine before making the first flight and it appears to have had no ill effects. Worst case in-flight was 100C peak during the initial max gross climb testing at 60 knots to 10,000 ft on a nice 98 deg Florida day (PAP Test Card #5 at max gross).

The issue of the gearbox running safely running at say 210 or 220 has not really been addressed. The question is why is it running hotter than the "normal" 170 temps that have been observed on other installations. This is a different engine and cooling configuration that those where 170 is considered normal. Viking appears to have no problem with a 220 max on the 110 gearbox.

Charlie: Just curious how the coolant and engine oil temps are tracking the GB temps, are you seeing the same trend lines as power, airspeed, and altitude change?

John Salak
RV-12 N896HS
 
thank you john. i knew the 110 had a higher rating, surprised to read of the lower temps. for mechanical parts in this unit.
 
The reason I am using 75w -145w synthetic is because that is what Viking requires.

I cannot say that 170 is "normal" as there are very few folks running the same set up that I am running. I.E. 22 degree pitch on a 72" 3 bladed prop on a 1.8L turbo honda engine. Most set ups are quite different. Most folks are using the gearbox on 1.5L Honda engine on a Zenith with a few RV12s.

I have an email in to Jan at Viking asking him about his suggestion/preference on routing cooling lines to an oil cooler but I have not heard back from him yet.

I did a few hard climbs yesterday pulling 34" MAP climbing about 1000+ft a minute climb for about 7-minutes. I started the climb with the box about 140F and it was at 175F at the end of the climb.

My engine temp stays at the 185F thermostat temp 98% of the flight, with the cold side of the thermostat loop between 135F and 155F depending on the RPM. To put this another way, I can speed up to 4800 RPM in level flight and the coolant temp on the hot side stays at 185 (in this cool weather). But the box temp will climb up to 195 may be higher if I run the engine at that speed longer.

I hope to validate the box temp sensor in the next few days.
 
Last edited:
I did a few hard climbs yesterday pulling 34" MAP climbing about 1000+ft a minute climb for about 7-minutes. I started the climb with the box about 140F and it was at 175F at the end of the climb.

My engine temp stays a

What is your RPM during the climb
 
What is your RPM during the climb

MSL it is 4200rpm at about 32" MAP and of course the MAP starts to reduce as altitude increases. Or obviously if I hold the MAP at 32 inches, the RPM increases with altitude. These are rough numbers from memory.
 
so i have to ask what is probably dumb question but why is the max 180 deg.? the faucet on my kitchen sink can take higher temps. does it have anything to do with the max temp some additives can operate in without breaking down?

Bob, I cannot say why Viking lists that temp, but it is what Jan told me.
 
Back
Top