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Broken RCV 58 CD


Paul Marsh
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The mod on the carb looks to have some threads. My assumption is that the previous owner has a nipple installed and routed the oil from the case vent back to the carb 

RCV instructions also state to use bearing retaining compound when reassembling the bearings. So if the engine was previously taken apart and the retaining compound skipped that may have caused the outer races to spin and the resulting scoring caused by any debris present within the engine.  

Edited by Manish Chandrayan
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Good point re routing the crankase vent back to the carb Manish, it would explain the threaded hole.

 

As I've said in previous posts, I'm becoming less inclined to try and repair it, as it has an unknown history regarding fuel etc. I'd rather spend the money on what looks to be a better one on eBay or similar.

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3 hours ago, EvilC57 said:

Good point re routing the crankase vent back to the carb Manish, it would explain the threaded hole.

 

As I've said in previous posts, I'm becoming less inclined to try and repair it, as it has an unknown history regarding fuel etc. I'd rather spend the money on what looks to be a better one on eBay or similar.

worth keeping for spares, or sell it as spares. I would buy it for spares, just in case.

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I’ve just got around to having a closer look at the engine, having stripped it down a bit further.

 

Damage appears to be confined to the conrod big end. Having removed the circlip and remains of the big end bush from the crank pin, the pin itself seems OK - maybe just needing a bit of a clean up.

 

The inside of the cylinder and the piston seem perfect, with no scoring that I can see or feel.

 

I called Weston UK yesterday, and they quoted £10.50 (inc VAT) for a new conrod, and £19.99 for a crankshaft - but I don’t think I’m going to need that. So for just over a tenner, I think I might try and get it going again, after a good bath and a cleanup to make sure I’ve got rid of any conrod debris.

 

It’s still worrying though, as to how the big end came to seize in the first place.

EB9CDE08-816F-47B5-BFE5-5B2BF75FEF27.jpeg

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35 minutes ago, Piers Bowlan said:

Could it have got too hot by running lean and/or not getting enough lubrication for some reason?

Faulty conrod?

Who knows? That was my thought too.

 

As I said in an earlier post, it is inverted in the model. But the instructions specifically say it can be run inverted (like every other glow motor I’ve come across).


I’m careful to run engines on the rich side. I’d rather have the reliability over absolute peak RPM.

 

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22 minutes ago, alan p said:

need to check those bearings as well! unless its the light they look less than prime.

Yes, I’ll strip everything down as far as I can and give it all a thorough wash out; presumably in fresh fuel being the best thing.

 

Unless anyone knows better, I can’t get the rotating cylinder valve out, as looking at the exploded diagram here it seems to be retained by a large circlip, which once installed in the upper crankcase casting, can’t be accessed to remove it.

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12 minutes ago, EvilC57 said:

Who knows? That was my thought too.

 

As I said in an earlier post, it is inverted in the model. But the instructions specifically say it can be run inverted (like every other glow motor I’ve come across).


I’m careful to run engines on the rich side. I’d rather have the reliability over absolute peak RPM.

 

 

Running engines rich on either needle is bad for them. In the case of a 4 stroke you only ever have oil in the crankcase and if you run the engine rich you end up with unburnt methanol in the crankcase. This dilutes the oil and makes it less able to do its job. Rich running also reduces reliability as the engine/plug may be running at a lower than optimum temperature causing a flameout. We have all seen an engine make it all the way to the runway and then die on throttle up. This is usually a rich cut caused by rich slow run tuning. Running the engine rich also leaves methanol in the crankcase which attracts moisture and causes rust. 

 

Its also, as a general rule, impossible to run an engine too lean as they will overheat/stop within a few seconds so this whole idea of running an engine lean for ages and having it cook itself is not actually correct. Usually they overheat due to poor cooling when in a cowling or suffer lean cuts due to incorrect tank placement causing a change in the fuel head and subsequent change in tuning. 

 

Fuel with excesses of oil and nitro also do not help at all and this is why i recommend the 5/15 mix for everything not a laser. 

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1 hour ago, EvilC57 said:

Yes, I’ll strip everything down as far as I can and give it all a thorough wash out; presumably in fresh fuel being the best thing.

 

Unless anyone knows better, I can’t get the rotating cylinder valve out, as looking at the exploded diagram here it seems to be retained by a large circlip, which once installed in the upper crankcase casting, can’t be accessed to remove it.

The circlip is to retain the cylinder bearing. The case needs to be heated, placed on a wooden surface and the cylinder then pushed down from above. Best done with a press, I got away using a softish alloy tube and a mallet.

 

This thread may be of use    

Edited by Manish Chandrayan
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Right, time for an update and some questions.

 

I decided after all that as it seemed only a new conrod was required, I’d go for a careful cleaning of the the engine, followed by an equally careful rebuild.


I managed to remove the rotating cylinder with the aid of a heat gun, a small wooden drift and a rubber mallet. The large ball race then being exposed. This felt slightly gritty, and on washing it out I noticed a fair amount of what looked like aluminium swarf in the bottom of the plastic container I used as a bath. The bearing still felt slightly gritty but was perfect after being kindly blown out by a friend with a compressed air line.

 

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0091D17B-7017-458C-A6D9-EC0BD631B657.thumb.jpeg.ab9be777f1690a86d304f3bb81ae7f9e.jpeg


 

Fitting the new conrod with the lubrication cutouts at the front, as suggested by Martin Harris and others in the thread suggested by Manish just above, gives the conrod an offset toward the front of the piston (see pic below) - I know the crank pin circlip is not fitted yet. Can this be right if it’s not in the the middle below the piston? It could be argued that there should be another washer forward of the big end, however none was fitted originally, and no washers at all are shown on the manufacturer’s exploded drawing of the engine.

 

157CC91B-6190-4335-A0E0-202746E0219D.thumb.jpeg.b18fc7dacbc89958b3f276ec5b388bc5.jpeg
 


Looking at the remains of the old conrod compared with the new, you could almost believe there was no oilway in the big end. Once the rest of the engine is sorted, I might try filing into the remains of the big end to see whether I can see any trace of the hole that should be there.

 

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8C097AE2-83B8-4379-BBF2-44856BF80DE1.thumb.jpeg.4b431efac1442c3b4326ccf23ac00694.jpeg

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2 hours ago, Paul De Tourtoulon said:

Are you sure that the swarf does not come from the bearing cages ?.

No I'm not sure. The cylinder bearing is running smoothly now, and my understanding of other people's efforts at replacing it leave me a little reluctant to try it unless I have to.

 

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1 hour ago, Jon - Laser Engines said:

Did you clean up the crank pin? any left over material stuck on the pin will cause the rod to fail a second time. It must be very carefully cleaned and inspected closely with a strong magnifying glass. 

Yes I did. I picked off the remains very delicately with a scalpel, and used a small soft wire brush afterwards. I didn't want to attack it with wet & dry and risk reducing the diameter. It looks (under a x7 magnifying glass) and feels completely smooth now.

 

The brass washer from the crankpin was more of a problem. That had some stubborn deposits of aluminium from the old conrod on one side of it. This I cleaned off using very fine wet & dry (used wet) in a circular motion on the end of my finger against a smooth surface. Being careful to remove all the aluminium, but none of the brass.

 

I can only do what I can do to ensure it's perfect during reassembly. If it fails again it'll go in the bin, and I'll turn my attention back to eBay for a replacement engine.

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On 04/08/2022 at 14:32, Jon - Laser Engines said:

 

Running engines rich on either needle is bad for them. In the case of a 4 stroke you only ever have oil in the crankcase and if you run the engine rich you end up with unburnt methanol in the crankcase. This dilutes the oil and makes it less able to do its job. Rich running also reduces reliability as the engine/plug may be running at a lower than optimum temperature causing a flameout. We have all seen an engine make it all the way to the runway and then die on throttle up. This is usually a rich cut caused by rich slow run tuning. Running the engine rich also leaves methanol in the crankcase which attracts moisture and causes rust. 

 

Its also, as a general rule, impossible to run an engine too lean as they will overheat/stop within a few seconds so this whole idea of running an engine lean for ages and having it cook itself is not actually correct. Usually they overheat due to poor cooling when in a cowling or suffer lean cuts due to incorrect tank placement causing a change in the fuel head and subsequent change in tuning. 

 

Fuel with excesses of oil and nitro also do not help at all and this is why i recommend the 5/15 mix for everything not a laser. 

Going back to this earlier post. May I just defend myself:

 

By saying that I run engines on the rich side, I'm following the manufacturers instructions; in that as per the instructions for both 2 and 4-strokes, I run them slightly to the rich side of peak RPM when on the ground.

 

I.E. In accordance with the following diagram, which appears in the instruction manuals for a number of OS engines.

 

img099.thumb.jpg.c1c556a7f83b0061dd7a1e40c5d98435.jpg

 

And also:

The instructions for the RCV58-CD which say, "Main needle (high speed) adjustment: The main needle should be adjusted with the engine operating at full throttle. The engine should be leaned out until the RPM peaks, then enritched a small amount. This will allow for the leaning out that normally occurs in flight.".

 

The instructions for an OS MAX-25FSR I also own, which say, (after running in) "After six to ten flights, it should be possible to run the engine continuously on its optimum needle setting. This setting is with the needle valve adjustment 1/4 to 1/2 turn on the rich side of the position at which the engine reaches its very highest speed. Your engine can be said to have completed its running-in period when it holds a steady speed at this optimum setting. Never attempt to gain a few more RPM by running the engine on a lean setting; it will run hotter and may eventually become damaged by over-heating.".

 

I'm just doing what the books say 🙂.

 

 

Edited by EvilC57
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I would have used some 400 wet n dry with oil on that pin. Its hardened so you arent going to do much to trouble the clearances. It might be a faff, but i doubt the treatment you described has done the job. I have cleaned up a fair few Laser crank pins and the bronze we use sticks like chocolate to a blanket. Its a real pain to get it off. 

 

Tuning by the manufacturers instructions. Yea ok, but dont forget that i am a manufacturer too and i dont recommend that old nonsense. Most engine manufacturers recommendations are deliberately quite conservative as they do not want to deal with a warranty claim from that one guy who's tank is mounted to the top of the fin, uses chip fat instead of real oil and directs the hot exhaust gasses at the cylinder head just to make sure it runs at 300'c. If you arent that guy, you do not need to be so conservative. I try to work on the basis that he people i speak to are not complete numpties so make recommendations intended to let them get the best performance rather than playing it 'safe' 

 

That said, if you are running as rich as you can without seeing an rpm drop from peak revs then that is ok i guess but we are talking 1 or 2 clicks, half a turn is insanity. You might as well not bother tuning it at all if you are just going to open it half a turn the moment you get it right. Again though, a max 25? that was back in the castor days and not all castor was created equal. OS were probably trying to cover themselves against our hero using the lowest grade of castor he could find with added sand to help running in. A guy at the club told him the extra abrasive sped up running in dont you know? And that might sound far fetched, but its not. Some people actually do stuff like that. 

 

Anyway, for reference, engines go rich in flight, not lean. Yes there are extreme cases where they will eventually go lean due to very high rpm, and engines running on pipes are a whole other story, but bog standard engines doing normal things in normal models go rich in flight as they unload. 

 

In any case i wasnt trying to have a go at you, just trying to point out that running engines rich is not actually very helpful. I know that its a part of modelling folklore, but its wrong. 

 

And as the engine failed even though you were doing things 'by the book' what do you have to loose by trying a new approach? 

 

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Just now, Paul De Tourtoulon said:

I may de conjuring up the wrath of others but I still add some Castor oil in my methanol fuels.😉

 

 "just saying",,,,

 

Why? Its like saying you add lead to the petrol you tip in your modern car. 

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5 minutes ago, Paul De Tourtoulon said:

I may de conjuring up the wrath of others but I still add some Castor oil in my methanol fuels.😉

 

 "just saying",,,,

What is the rational behind adding castor? What proven improvements does it make? Why don't other areas of motorsport use castor...or do they?  The secret advantage of F1 teams to ultra endurance engines...add castor.

 

Great news I have 4 gallons of Castrol R1 left over from racing 25 years ago..any bids? 🤣 

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47 minutes ago, Jon - Laser Engines said:

I would have used some 400 wet n dry with oil on that pin. Its hardened so you arent going to do much to trouble the clearances. It might be a faff, but i doubt the treatment you described has done the job. I have cleaned up a fair few Laser crank pins and the bronze we use sticks like chocolate to a blanket. Its a real pain to get it off. 

 

Tuning by the manufacturers instructions. Yea ok, but dont forget that i am a manufacturer too and i dont recommend that old nonsense. Most engine manufacturers recommendations are deliberately quite conservative as they do not want to deal with a warranty claim from that one guy who's tank is mounted to the top of the fin, uses chip fat instead of real oil and directs the hot exhaust gasses at the cylinder head just to make sure it runs at 300'c. If you arent that guy, you do not need to be so conservative. I try to work on the basis that he people i speak to are not complete numpties so make recommendations intended to let them get the best performance rather than playing it 'safe' 

 

That said, if you are running as rich as you can without seeing an rpm drop from peak revs then that is ok i guess but we are talking 1 or 2 clicks, half a turn is insanity. You might as well not bother tuning it at all if you are just going to open it half a turn the moment you get it right. Again though, a max 25? that was back in the castor days and not all castor was created equal. OS were probably trying to cover themselves against our hero using the lowest grade of castor he could find with added sand to help running in. A guy at the club told him the extra abrasive sped up running in dont you know? And that might sound far fetched, but its not. Some people actually do stuff like that. 

 

Anyway, for reference, engines go rich in flight, not lean. Yes there are extreme cases where they will eventually go lean due to very high rpm, and engines running on pipes are a whole other story, but bog standard engines doing normal things in normal models go rich in flight as they unload. 

 

In any case i wasnt trying to have a go at you, just trying to point out that running engines rich is not actually very helpful. I know that its a part of modelling folklore, but its wrong. 

 

And as the engine failed even though you were doing things 'by the book' what do you have to loose by trying a new approach? 

 

I agree with you Jon about the half turn being madness. I’m talking about one or two clicks, that’s all.

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1 hour ago, Chris Walby said:

What is the rational behind adding castor? What proven improvements does it make? Why don't other areas of motorsport use castor...or do they?  The secret advantage of F1 teams to ultra endurance engines...add castor.

 

Great news I have 4 gallons of Castrol R1 left over from racing 25 years ago..any bids? 🤣 

 

Edited by Jason Channing
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