Continue to Site

Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

  • Congratulations IDS on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Blower gear oil 3

Status
Not open for further replies.

patprimmer

New member
Nov 1, 2002
13,816
I work on a few blown alcohol injected drag race engines.

The gear box on the blower to drive the rotors needs oil to lubricate it.

Some are trying to convince me I should use 2 stroke oil as if the oil leaks past a seal and contaminates the fuel, 2 stroke is designed to burn.

While I agree, clean burning is a prerequisite of 2 stroke, so is being able to lubricate4 roller bearings in a very low oil, high fuel environment, and they will be formulated with those parameters weighing heavily, but I expect 2 stroke is NOT formulated to lubricate gear boxes.

My concern is the relative effect on octane rating of various oils on methanol in a failed oil seal situation. Does anyone know if any 2 stroke and gear oil manufacturers produce data about the oils octane rating and the effect it has on methanol's octane when mixed.

I would also like to know how good 2 stroke oil is at lubricating gears as this would not normally be a parameter when formulating it.

I really can't see me changing, but I am concerned some meat head is going to influence one of the car owners to change the oil. I would really like it if I had data, not just supposition to counter their arguments.

I think I already know that in this quest, I am shovelling it up hill with a pointy stick.

Regards

Pat

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
 
Replies continue below

Recommended for you

Pat, you know I'm kinda old so I'll tell you what one of the local hot shoes used on a chain driven 671 (now you know THAT has to be a looooong time ago)---Castrol R (bean oil). I think it was about the equivalent of SAE 50...I'm not sure, though. I also don't remember if he had a pressurized delivery or not. Sorry, it was in 1958 and I just remember the high spots.

Rod
 
Rod

Castor oil does seem to be the universal lubricant.

I wonder how it handles the EP in gears.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
 
Your the chemist, Pat. What about an EP additive. (Gad...Is that blasphemy or what)?

Rod
 
This chemist knows a lot about plastics and fibres and even chemicals to modify plastics, and a bit better than general knowledge of other stuff, but oil additives is an area where I have been caught short a few times by mouthing off what I thought I knew. drwebb is the guy that normally catches me. I hope he comments here as it seems he has real world experience formulating and testing oil compounds.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
 
i don't think there will be much data on the effect of a certain amount of oil on the octane rating of the fuel when contaminated. one thing is sure, the octane rating will go down and problably quite a lot because the type of molecules used as basestock for lubricants have very low octane ratings.

i wonder however, whether you should be worried about it. if there is a sligth leakage there would of course get some oil into the combustion chamber, but not necessarily more oil then the amount that pass along the piston rings into the combustion chamber. the effect of that oil is usually not very large, and normally does not lead to preignition.

as far as lubrication of the rotors is considered, a two stroke oil is not such a good idea. two stroke oils are designed to be used once only and then be burned - their oxidation stability is not very high and in normal applications that is not needed. when, however, you employ the two stroke oil for a prolonged time under higher temperatures, oxidation might well occur and problably give rise to all kinds of deposits that are unwanted on the rotors. a better choice would be an engine oil. engine oils have good thermal stability and oxidation stability and also detergent/dispersant properties that might prevent the build up of laquer and varnish. they also contain anti-wear additives that should be sufficient ("real" EP properties are problably not needed for the rotors). therefore i would choose an engine oil with say a minimum performance level of API CF or SE, in the appropriate viscosity - most likely SAE 30, 40 or 50, depending on how hot the oil gets in the rotors. if you would prefer a lower viscosity, a aviation type synthetic gasturbine oil would be a good choice, if you can get hold of it.

castor oil has no EP properties at all, however is sticks very good to metal surfaces and it's reputation is based on that - it can lubricate certain applications where mineral oils fail. however, apart from the good metalwetting capabilities, it is not such a good lubricant: it oxidizes vary rapidly and is not suitable for prolonged use at higher temperatures. you also must be willing to take machinery apart at regular intervals to clean out the deposits. for certain applications that is acceptable because it is the only lubricant that makes operation possible at all, but for most application a product with higher thermal and oxidation stability is to be preferred.
 
romke.

Thanks for your reply and you basically support my views with some expansion.

However you seem to have misread my question and also, I did not fully explain operating conditions in my OP. My bad.

The oil is to lubricate the gear drive for the rotors, not the rotors themselves. The rotors run with a small clearance and are wet by fuel which lubricates, cools and seals the rotor to housing interface.

The gears are mounted to the same shaft as the rotors and there is a seal to keep the gear oil from leaking onto the rotors. These seals occasionally have a catastrophic failure and leak the oil out in a few seconds. This can cause detonation in an engine that is already tuned to extract the maximum power for only a few seconds. This detonation normally results in major engine damage.

These parts are normally maintained regularly as they normally operate at extreme stress and are exposed to methanol or nitro methane fuels.

The seals sometimes fail due to attack from the fuels.

I believe the real answer is run the gears in gear oil and maintain the seals and check the oil level between rounds. If it drops at all, don't race.



Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
 
At first blush this seemed like a pretty bizarre suggestion, but the more I think about it the more I wonder. First understand that there's a lot more variety in 2T oil formulations than some other types of lubes (like 4T crankcase or transmission oils), so some may be pretty unsuitable, while others perhaps less so. In partucular, 2T oils used for injector/autolube systems (like on scooters) usually contain 25-35% solvent to facilitate mixing with the gasoline, and this solvent won't improve its lubricating properties in a gear application at all. That said, some of the base oils used in 2T oils also find application in industrial and automotive gear oils, so a high quality 'premix only' 2T oil (such as those marketed for racing applications) actually may not be totally unsuitable for the application, particularly with a short service interval like in drag racing.

As to what effects would be expected in a 4T MeOH/nitro system suddenly dosed with the oil I can't even guess. FWIW, the CIK-FIA rules for lubricants require less than +/-1.3 octane numbers change for their 2T oils in gasoline. So their list of homologated oils ( will all meet this requirement. That's the closest to 'data' I can think of.

So in principal it may work, but I agree with you and patprimmer that rather than relying on the combustion properties of the SC oil, the best approach is to be careful the seals don't fail!
 
pat,

thanks for the explanation. the way you describe it, there seem to be not many options, since when failure occurs, it happens all over sudden and the complete amount of oil gets into the engine that is working at its very limits in terms of octane rating requirement. under those circumstances any oil will deteriorate the octane number of the fuel/air /oil mixture to problably a catastrophic value indeed.

your suggestion as to check the seals prior to the race and not to compete when the oil level has gone down or the seals show some distress between starts, is possibly the only way to prevent or bring down the number of engine blowups.

the good thing then is that you can concentrate on choosing the oil on the basis of the lubrication requirements of the gears only.

one alternative for the gear oil would be a poly-alkylene based lubricant. there are 3 reaons for this. first you do not need seals that are compatible with both mineral oil and special fuels, but seals that are compatible with PAG and the fuels employed. the second is that PAGs might be less detrimental to the octane rating then mineral oils, and the third reason is they are good lubricants that can reduce wear and friction in gear mechanisms in comparison to mineral oils. in your case it might be interesting to look into them because there might be a chance that it is easier to find suitable seals, compatible with both fuel and lubricant.

see this link for info on seal compatibility:
 
Pat, since it is apparent that a "zero defects" program is the ultimate answer...How far fetched is the idea of using two seals? I had a rear end (no relation) that dumped oil on right hand corners...drove me crazy. Finally re machined the housing to take double seals. Problem solved as long as I replaced the inner seal on a regular basis, usually every three or four races or mid season.

Can seal failure be traced to run out, pressure in the gearcase that venting won't cure or, just crappy seals? Just some thoughts, as I know you have probably already done the failure analysis.

Rod
 
In my opinion, blower seals fail due to neglect or the wrong seal for the fuel used.

Alcohol compatible seals tend to shrink after exposure then drying out for some months, but come good again after a few minutes of operation.

Preventing this comes down to proper off season maintenance.

Rod

As usual, I like your basic real world approach. I don't know that there is enough room to install dual seals, but you can be sure I will be looking.

I will also be advising against 2 stroke and recommending proper gear oil, maybe PAG if I can get the right seal for PAG and the fuel.

Taking Rod's idea further, it should have back to back dual seals, one sealing the fuel out when under boost and the other sealing oil in when there is manifold vacuum. That way one seal is the right compound for the oil and the other is the best for the fuel.

I feel I saw some dual lip seals designed to work both ways. Two of them would be better still.



Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
 
Opps. Another possible cause of seal failure is backfires. They can be extreme and have been known to bend rotors and/or blow the blower off the manifold and into the crowd if restraint's are not used. For that reason, restraints are required.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
 
There are oils sold specifically for the gears on Eaton blowers, wouldn't that be a good choice? I'm sure they aren't loaded as much as on a drag engine.

I wouldn't think any normal amount of leakage of any type of oil from a blower seal on a blown alky drag engine would have any detectable effect on such an engine.

Are the seals arranged to keep oil out of the lobes, or air out of the gear drive?
 
I must admit I only ever had one seal fail. Used a petrol blower on methanol.

We had a blower specialist rebuild it. We never lost oil since then. I am really collecting supporting evidence to try trying to prevent owners listening to folklaw. That is unless someone here qualified to comment convinces me otherwise.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
 
I don't remember what kind of trans oil I had in my old ~1969? Kawasaki Bighorn (350 single, 2-stroke), but the trans/engine seal failed and it detonated a bunch. Traded that pig in when I bought a 750 triple in 1972.

Gold is for the mistress - silver for the maid
Copper for the craftsman cunning in his trade.
"Good!" said the Baron, sitting in his hall
But iron - cold iron is the master of them all.
Rudyard Kipling
 
Pat,

Further define the "2 stroke" oil they refer to. Are they advocating the stuff one would put in a lawn mower or chain saw or the HD oil for two stroke diesel engines where the roots blower is an integral part of the process?

If the former, then I defer to the conversation above and say that I have no opinion nor experience, except that I can't see me putting what I have put into plenty of 2 stroke gasoline engines in any gear box that I respect.

If the latter, then the idea might have merit as I had to deal with the old 2 stroke Detroit Diesels a lot in my past and they require a straight 40 weight and I can't remember the SAE letter codes required (I'm sure Google would produce it.) Multi-vis oils just wouldn't work in those engines no matter how hard it bacame to find straight 40 wt and no matter how hard the uninformed tried to get around it. But I am not sure that the failure of the multi-vis oils to perform in that series of engine was necessarily blower related. I just know that those Detroits burnt and blubbered lots of oil. They were rated to consume one gallon per 10 hours of operation straight out of the O&M manual. That was about a full day's running on our roads, so it was literally a gallon at every fill up.

Since most straight gear boxes call for 50 weight anyway, then the 40 weight grade for DD engines might be right in the neighborhood of meeting what they advocate.

rmw
 
Status
Not open for further replies.

Part and Inventory Search

Sponsor