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MVVS 1.5cc diesel run.

Old 05-03-2013, 08:56 PM
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Bill Adair
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Default MVVS 1.5cc diesel run.

Finally got around to running one of the two MVVS 1.5cc diesels that I got from the late Ralph Wentzel's estate.

I mixed up some of the MVVS recommended break-in fuel (45% Ether), and went out to the field to run the little bugger. My friend Mark Hansen was there to help, as he is our club diesel guru.

The first attempts to flip start the 09 didn't go well, and soon wore both of us out taking turns flipping. We had some healthy pops, but no sustained running.

As a last resort I got out my 1/2A Miller (Kavan) starter, and proceeded to do the un-thinkable (to some), and resort to a little assistance from Thomas Edison. The Miller starter never fails to amaze me, and has started 2.5cc glow engines with no effort at all. We made sure the engine was not too wet by hand flipping it first, squirted a little prime against the side of the piston, and prepared for the worst of the sad results attributed to electric starter use on small diesels.

Since I don't have a spinner for the MVVS engine, and wanted to get the starter cone well centered, I just turned the prop CW against compression, and pressed the starter cone over the prop nut firmly, and then blipped the starter button. We were rewarded with almost immediate success as the engine burst into life, and only needed a little needle and compression adjustment to settle into a slightly rich run. Subsequent runs did not require any electric starter help, but did require a wet prime. At least we knew our hand flipping had the needle and Tommy bar set very close to optimal.

Went out again today and got about a half dozen more runs, all with hand starts using a wet prime. In the process I noticed that the engine would not draw fuel well when hand choked. The fuel moved up the line and inch or so per flip, but fell back immediately. Seems there is an air leak somewhere, and I'm going to check that out next. It may explains the difficulty hand starting, but the quick results on electric starter.

Fuel was the recommended MVVS mix, but with 2% Amsoil Cetane booster added. Prop was an MA 8X4.

Day one only produced momentary 10K rpm peaks, which was about as lean as I dared to set it. Today I got it up to 10.9K rpm, after another half dozen runs with complete cooling between. Seemed happy at that setting, but I didn't leave it there any longer than it took to read the tach.

If anyone here has experience with this MVVS 1.5cc diesels, I'd appreciate any comments. The fit and finish were superb, and the internals were absolutely spotless.


Bill











Old 05-03-2013, 09:22 PM
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Default RE: MVVS 1.5cc diesel run.

Bill my experience with these engines (3 or 4 examples) is that they are not particularly easy to hand start-especially from new-but are well made and run extremely well once started. I too have had to resort to the electric starter in the past! I would say that 11K on a Master 8x4 (not a light load) on a new engine is doing very well indeed. Mine has perhaps 20 minutes accumulated running on it-and still has a lot of running-in to do yet! The poor hand starting meant that I relegated it well down the list of 'user' 1.5 diesels for my building program. That being said it's certainly no worse than a typical ABC Russian Elfin 149-but I have engines that are far more tractable-and for the sort of classes I fly 1.5 diesels in, (various FF and vintage duration) I need one that starts fast. My MVVS 1.5D will no doubt find a use in an R/C model in due course....

[FWIW the other three I have handled over the past 15 years have been worse hand starters that my example-which isn't saying a lot.......but I have no idea whether they were still new at the time-or at the other end of their life...............]

ChrisM
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Old 05-03-2013, 11:40 PM
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Default RE: MVVS 1.5cc diesel run.

Hi Chris,

Thanks for the info on your MVVS 1.5cc diesel experiences. That pretty much says it all.

Fortunately, I'm not against using an electric starter when necessary, and since I don't compete in any model airplane events it won't be an imposition.

The poor fuel draw does bother me though, and I intend to look into that.

I removed the plastic back plate to inspect the interior before ever turning the engine over, but I'm sure I got it seated properly without damaging the paper gasket. The fit of the crank in the case is very good, so I don't suspect air leaks there.

One suspicion I have, is that the rather long prop screw could possibly have punched through the un-drilled center of the crank, and into the intake area (below the venturi). The MA props I bought (because I could not find even one 8X4 wood prop locally) were difficult to keep from spinning off, even before resorting to the electric starter. My friend Mark said the same thing happened with one of his MVVS diesels, until he removed the fuel tubing he had used to center the prop hub on the screw. He noticed that I had done the same thing, and sure enough when I reluctantly removed the fuel tubing bushing from the prop screw I was able to torque the screw enough to hold the prop. Removing the short length of fuel tubing didn't make sense to me, but I did it because Mark insisted it worked for him. I'll keep you posted if I find anything to support that little suspicion of mine.

Bill
Old 05-04-2013, 12:12 AM
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Default RE: MVVS 1.5cc diesel run.

I don't like a slotted screw prop fixing setup on engines this big either Bill (the 2cc has it as well)-you could replace it with an allen head one (try www.microfasteners.com) for more torquing-or simply find a replacement 5mm metric machine screw of a suitable length, cut the head off it, and fit either a conventional hexagon nut or a 5mm spinner [the one for the OS Max 10 series will fit beautifully] if you want to use a starter.
Some of my more frustrating memories as a young modeller were with the DC Bantam (and later the DC Wasp) engines-which also used a machine screw -in this case 6BA (smaller diameter than the Cox 049s' 5-40 ) to retain the prop. The DC 'Quickstart cam' fitted behind the prop-interspersed between the back of the prop and the knurled prop driver-the plain face of the quickstart cam did not grip the prop as tightly, and the distinctive 'crack' of the prop loosening up as the spring starter fired it over compression and the motor almost caught-was a familiar experience! Eventually I became good enough to flick start the little things.........curiously I never had the same slippage problem with the diesels in the DC range-also 'Quickstart' equipped-but they all had either a prop nut or a spinner nut you could do up really tight......!

On the fuel draw thing-check the backplate seal by simply turning the engine over with the backplate completely submerged-any leak will show bubbles venting-but I suspect it is simply a case of too big a venturi size-in which case you can a) get someone to turn up a smaller bore venturi (start with 0.5mm or 1mm smaller in inside diameter), or b) sleeve down the existing one with some brass or K&S aluminium tubing-I imagine (and I'm not going to go rummaging to dig my one out to check) that it will be a metric bore size-so (ideally) you'd want to try and get some metric rather than imperial size tubing [K&S may well do their tubing in metric as well as imperial sizes......and simply epoxy a piece (or two pieces) in place.

As a quick and nasty check-get a piece of wooden dowel (you must have some in your scrap box-even some broken wing dowel!)-about the right size-split it diametrically, and block off half the venturi by wedging it between the spraybar and inner wall of the venturi (a old and tried fix!) If your fuel draw doesn't improve considerably after this-then you have an air leak somewhere else....if it does-then you've both confirmed the problem and have the solution-a smaller choke size! [not a new problem-the old Frog 500 from 1950 was notorious for poor fuel draw-and the 'half venturi' plug was a quick and effective fix-and I've heard of people applying the same fix to the dear old DC Merlin on occasions-though I've never found it necessary...

ChrisM
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added in Edit: a quick check of K&S products confirms they do sell metric tubing in brass and aluminium-and a second check of Tower Hobbies site confirms that they have a range of metric sizes in stock in both thick and thin wall formats............
Old 05-04-2013, 06:16 AM
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Default RE: MVVS 1.5cc diesel run.

I only have one of the 1.5s maybe 8 years , it has been flown in some sort of a high wing trainer/sport do not remember , after a number of flights went to airplane heaven
and engine back on the shelf . It was wearing an 8x4 wood zinger, original slotted screw to hold the prop davis 1/2 A fuel. I have run it a few times since on the bench9500
to 10000 if my old memory is right. It wold hand start with a prime down the carb no starter used maybe 10-12 flips and off, carb stock no restrictor (rc type) , a good starter and runner no issues compression is quite high no blowby or leakage it was re -run just a few months back martin


JUst checked back Fiery in Aug of 2012 stated 11500 on a 7x4 so the approx 10000 on the wood prop appears in line
Old 05-05-2013, 07:06 AM
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Default RE: MVVS 1.5cc diesel run.

I feel fortunate. I have three of the MVVS 1.5's and all three started easily and ran well. One had a loose venturi but that was just a loose screw (guess I missed that when checking). I do not have extensive run time on them but they are run-in and all run well. I use a commercial model diesel fuel. Prop was 8x4.

George

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Old 05-05-2013, 07:22 AM
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Default RE: MVVS 1.5cc diesel run.

George sounds like my numbers in line, would like to find a metal backplate to replace the plastic one , only have one of the 1.5s but 3 of 2.5s, 2 still new .

Like yours no issues easy no issue start ad run, have had no issue with stuck contras in either the 1.5 or 2.5s martin
Old 05-05-2013, 01:24 PM
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Default RE: MVVS 1.5cc diesel run.

Chris,

Good advice there, and it sure gives me some more things to check.

Fortunately, my MVVS is getting easier to start as it runs-in, and I'm getting to like this engine in spite of the initial hard starting.

I keep refereeing to the engine as MVVS, but the outer box on all three of them is labeled Modela. The crank case castings show MVVS on all of them, and I've read most of the previous threads on the forums about how that name change came about,

The contra piston on mine was a perfect fit, and moved easily once the engine was primed and flipped over.

I'm out of the run-in fuel now, but will mix a batch of more appropriate fuel today, with a bit less Ether since that is in short supply.

By the way, my friend Mark is going to share a gallon of Ether with an engineer friend who works at a foundry. He found that he can order it for a reasonable price, and it can be delivered to an established business address. I'll let you all know the total cost with shipping, which should be reasonable as it's available here in Oregon.

Martin, I wouldn't worry at all about the plastic back plate, as mine is very well made, and can be torqued very tightly with the large hex socket thats cast in. I bought a stainless bolt that was a good fit, and wrapped the head of the bolt with a layer of blue masking tape to protect the plastic back plate.

George, very encouraging news on your MVVS diesels, and I hope mine all handle like yours.

No doubt there were some issues with these engines at one time, as my friend has had three of them, but only managed to get one of them to run! I suspect this may have been early in his diesel experience, and may not be the case today.

Will try some Olde English mix for this batch of fuel, as I can easily add more Ether if necessary.


Bill
Old 05-05-2013, 02:28 PM
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Default RE: MVVS 1.5cc diesel run.

Chris thx for the advice on the hex back plate I have a complete set of drivers 4-17mm 10,, too small 12 too big no 11mm in set, the hex head bolt sounds like a winner I have no need to remove at this point but would be nice to be able too if needed. my box does read Modella but also MVVS in large letters also martin
Old 05-05-2013, 04:17 PM
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Default RE: MVVS 1.5cc diesel run.

Martin,

Your right. I missed the MVVS name on the box completely, because it's only on the back side.


Just finished mixing some Olde English fuel for my MVVS, and noticed that the previous evaporated sample of the breake-in fuel had not separated into distinct layers as the previous samples had.

Could it be that Amsoil Cetane Booster actually binds the Castor and Kerosene ingredients? That's the only difference in these samples, as I didn't have any Amsoil on hand for the first batches.

Bill
Old 05-05-2013, 04:35 PM
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Default RE: MVVS 1.5cc diesel run.

Bill the cetane booster amsoil hexyl nitrate did its job no separation martin
Old 06-07-2013, 05:40 PM
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Default RE: MVVS 1.5cc diesel run.

Got a bit more running on the MVVS 1.5cc diesel today. Using the same 8X4 MA prop, and Olde English mix, with a bit of Amsoil DII added.

Nothing changed, but I did re-tighten the back cover a bit. Same lack of suction as before, but I've raised the tank to limit the fuel drain back to the tank.

RPM is up again, and peaked out at 11.9K rpm by the end of the day, but only for a moment before I opened the needle again. As before, cold starting is a struggle, so the electric starter was used.

I'm going to take it off the test mount, and check for leaks before running it again.

Bill
Old 06-10-2013, 06:55 PM
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Default RE: MVVS 1.5cc diesel run.

My MVVS air leak solution is pending, but I'm not sure it will be easy! Seems the air leak is actually around the needle valve itself.

I missed it all this time because the U-shaped detent spring is snug on both sides of the knob, and the needle extension is very short. This kind of play is easily spotted with longer needle valves.

What's even stranger is that my other two NIB MVVS diesels don't appear to have near this much needle play.

Now the question is how to seal the needle valve, and still allow easy adjustments...????

On glow engines it's quick and simple to seal the needle, because silicone fuel line is very soft and flexible. However, I use Tygon fuel line on all my diesels, and that stuff is almost rigid in comparason. Worse yet, it seems to harden even more with exposure to fuel and weather. Will silicone line deteriorate too quickly in this application, or is there an alternative such as Neoprene, or surgical tubing that might work better?

Never had this problem on any of my other diesel engine.

Thanks in advance for any advice.

Bill
Old 06-10-2013, 07:17 PM
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Default RE: MVVS 1.5cc diesel run.

I'm assuming that we are talking of a leak around the needle valve thimble threads, caused by -essentially-too poor a fit between the respective male and female threads. You're right-silicone tubing will not serve you well in this respect, as it swells and softens in the presence of diesel fuel. My thoughts would-for this particular situation-lean towards wrapping the spraybar male threads with plumbers teflon conformal tape-which is very thin, very stretchy, and tends to meld into itself when wound or wrapped around a thread. [this is after all-exactly what it is used for in plumbing-sealing threads!]. I'm not sure whether you'll be able to do it in situ-as the ratchet spring may get in the way-but you'll still need the spring to hold the needle setting in anycase. [the tape probably CAN be fitted with just the needle valve removed, and the spraybar still on the engine-but it's likely to be a fiddly job! .....] Alternatively you can dis-assemble the NVA and install the tape-but you'll need to check that the larger diameter with the tape will still fit through the hole in the ratchet spring!

Of course your other option is fitting a different needle valve assembly.......off the top of my head the MVVS/Modela one is about 3.4mm diameter-so an OS FP15 or 20FP standard one would be a suitable substitute............
Old 06-10-2013, 10:24 PM
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Default RE: MVVS 1.5cc diesel run.

Chris,

Thanks for the tips. I hadn't thought about replacing the needle valve assembly, but I do have several options there, with some spares on hand.

Teflon tape would be difficult to apply for the reasons you stated, but our pharmacy stocks thick and thin wall surgical tubing, and ACE Hardware has something called clear Neoprene I'll check out. Lawn mower shops may have rubber fuel tubing that might work, so that is another option.

The MVVS started easily today by hand, but as usual got a little stubburn after warm up. The air leak is most likely responsible for that.

Bill
Old 06-10-2013, 11:36 PM
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Default RE: MVVS 1.5cc diesel run.

Possibility of lightly tinning the thread with solder and working the needle back to its position?
Old 06-11-2013, 12:47 AM
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Default RE: MVVS 1.5cc diesel run.

Thanks for the interesting idea.

That might actually work, but I'd want to have a tap and die set of the proper size on hand, just in case it didn't. Also, the solder I have (electrical stuff) might not stand up to vibration in the long term.

No doubt the needle and spray bar threads are metric, but my limited set of taps and dies are not.

Bill

Old 06-11-2013, 01:37 PM
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Default RE: MVVS 1.5cc diesel run.



Hi Bill, These 1.5cc Modelas are very tight when new. I used a 9X4 for initial hand starts.

As soon as it restarted easily with the 9X4; I switched over to a 7X3. For running in, these engines need

to turn up with a low load prop. Using an 8X4 will never get your engine properly broken in.

My 1.5cc was still tight even after 50 minutes of short high rpm runs and cool down breaks.

It soon was turning a 7X4 at 13,800 rpm on the ground, so I took to the air with it using a

7X4 cut down to 6.7" X 4. This engine was used to power a 260sq" combat wing. I ended up

using a 7X6 cut down to 6.2" diameter for flying combat(UK style) on 45' X .012" lines.

I was using the following fuel mix: 43% kerosene, 20% Castor, 35.5% ether and 1.5% amyl nitrate.

Please remember, for proper break-in, get the revs up with a smaller diameter prop and then

when that's accomplished, switch over to your flying prop. Best of Luck;

Tony
Old 06-12-2013, 04:57 AM
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Default RE: MVVS 1.5cc diesel run.


ORIGINAL: Bill Adair

Chris,

Thanks for the tips. I hadn't thought about replacing the needle valve assembly, but I do have several options there, with some spares on hand.

Teflon tape would be difficult to apply for the reasons you stated, but our pharmacy stocks thick and thin wall surgical tubing, and ACE Hardware has something called clear Neoprene I'll check out. Lawn mower shops may have rubber fuel tubing that might work, so that is another option.

The MVVS started easily today by hand, but as usual got a little stubburn after warm up. The air leak is most likely responsible for that.

Bill
You might try blue Loc-Tite. Hold the assembly needle down so any excess will run back out, not in, and apply to only the outer half of the threads. It worked for me on an ill-fitting needle for an Elfin 1.49 ABC.

George
Old 06-15-2013, 03:35 PM
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Default RE: MVVS 1.5cc diesel run.

Hi Tony,

Thanks for the MVVS break-in tips, and diesel fuel formula for my engine.

Diesel combat was very popular here in the NW, but seems to be on the decline of late. Unfortunately, my skills are too far gone for any C/L competition, so I'm just enjoying sport flying while it lasts.

Bill
Old 06-15-2013, 03:43 PM
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Default RE: MVVS 1.5cc diesel run.

Hi George,

What a great idea!

I never considered Locktite for that, but may give it a try if the fix I'm working on does not do the job.

Bill
Old 06-15-2013, 03:44 PM
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Default RE: MVVS 1.5cc diesel run.

Bill my 09 over the years has survived several planes that did not over the years with no ill effects still hums martin
Old 06-17-2013, 11:43 PM
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Default RE: MVVS 1.5cc diesel run.

Martin,

That's good news, as I hope to use mine in the future.

Think I have the air leak fixed, but probably won't get to run it until later this week (rain expected again).

Bill

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