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  #631  
Old 11-10-2020, 08:38 AM
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DanH DanH is online now
 
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Quote:
Originally Posted by rv6ejguy View Post
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.
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  #632  
Old 11-10-2020, 10:18 AM
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Quote:
Originally Posted by DanH View Post
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?
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 448.3 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
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  #633  
Old 11-10-2020, 01:00 PM
12vaitor 12vaitor is offline
 
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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
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  #634  
Old 11-10-2020, 01:21 PM
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Thanks for posting your experience.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 448.3 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
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  #635  
Old 11-10-2020, 03:22 PM
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Quote:
Originally Posted by 12vaitor View Post
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.
Three-gear box?
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  #636  
Old 11-10-2020, 04:37 PM
Tomcat RV4 Tomcat RV4 is offline
 
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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
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  #637  
Old 11-10-2020, 11:27 PM
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charosenz charosenz is offline
 
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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.
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Last edited by charosenz : 11-10-2020 at 11:39 PM.
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  #638  
Old 11-10-2020, 11:38 PM
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Quote:
Originally Posted by Tomcat RV4 View Post
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.......
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https://vansairforce.com/community/s...158610&page=70
2021 Dues paid

Last edited by charosenz : 11-10-2020 at 11:46 PM.
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  #639  
Old 11-11-2020, 06:22 AM
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DanH DanH is online now
 
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Quote:
Originally Posted by charosenz View Post
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/...age=1#comments

Quote:
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.
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  #640  
Old 11-11-2020, 09:18 AM
12vaitor 12vaitor is offline
 
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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
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