Quarter Scale Merlin V-12

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ddmckee54

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OMG - It's alive?

You didn't think it would run? Yeah - right, just like Howard Hughes was only doing a "Taxi" test of the Spruce Goose.

Probably had to chisel the grin off your face, fried lip and all.

Congrats on the first run. You ARE going to video the second run, right?

Don
 

mayhugh1

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One of the last ends to tie up was the protection of the electrical connections inside the Futaba connectors used on the Hall sensor cables going to the ignition modules. This involved making a pair of protective covers by shrinking a length of heat shrink tubing over the connector while leaving a bit of overhang on its open end. A mating male connector, used during the shrinking process, prevented the open end from closing up. The cover slides over and protects the seams between the mated connectors on the ignition modules. Silicone was used to seal the cable to the rear of the tubing.

The step that I've been dreading since the beginning of this project was filling the engine with coolant. The are 76 coolant seals in the engine, and 52 of them are inaccessibly buried in the head assemblies. Although I vacuum tested those assemblies just after the heads were married to the cylinder blocks, my gut never made its peace with this particular feature of the engine's design.

I slowly filled the whole system with about 1-1/2 liters of automotive anti-freeze while checking for leaks, and then I left the engine sitting for several hours. Placing the coolant reservoir at the rear of the engine so it was level with highest point in the coolant loop was a great help, but another half inch or so of height would have been even better. If I had it to do over again, I would add a second filler cap to the top of the header tank at the front of the engine.

Sure enough, a bit of seepage showed up near the front of the starboard head assembly and also near the rear of the port assembly. With the engine filled with coolant but still no prop, I attempted to start it with the carb settings untouched (or so I thought) from my previous accidental start. I got a few pops and then nothing. After several seconds of cranking, raw fuel began pouring out of the carb's intake. My first thought was that I had an issue with the fuel loop. If the pump pressure is too high, excess fuel can be forced out of the bowl vent and create a similar symptom. However, after additional testing, I realized the flooding occurred only while the engine was being cranked.

I was about ready to remove the carburetor (Perry 9400) when I noticed the starboard coolant return hose rubbing against the high speed needle. I could see the hose changing the needle setting as the throttle was moved back and forth. The o-ring friction that's supposed to stabilize the needle setting against vibration wasn't adequate against the moving silicone hose. A simple tie-wrap solved the problem. The remarkable thing about all this was that the throttle had been moved many times since that hose was installed, and yet somehow the needle ended up at just the right setting to allow the engine to start up so easily the very first time.

At this point the needle was sitting at 2-1/2 turns open from its fully closed position which happens to be close to the recommendation in the application note that came with the carb. I went back over my notes for my last radial build that used a very similar Perry carb. That engine had run best with a needle setting 3/4 turn from fully closed.

I reset the needle to 3/4 turn and let the engine sit for a few hours to dry out before attempting a restart. This time the engine started up and ran although a bit rough. I could tell from the exhausts that the cylinders in the starboard bank were firing only intermittently. This time my wife was videoing the run on her iPad.

[ame]https://www.youtube.com/watch?v=2lw-6he7qFY[/ame]


While running there's no oil or smoke coming out of the exhausts - a very good sign, but the coolant leaks opened up some as the head temperatures rose. After shutdown, about a teaspoon of coolant dripped from the engine.
After allowing the engine to cool I made another run. This time I could feel the throttle response beginning to show up, and the engine easily rev'd up even though the starboard cylinder bank was still only intermittently firing. Before quitting for the evening I was able to eliminate the Hall sensor and ignition module as the source of the problem. The problem seems to be in the starboard distributor, and I may have a small phasing issue with the rotor.

I was pleasantly surprised to see the engine which has so much internal gear friction run as well as it did without the benefit of prop momentum. The electric starter also seems to be holding up.

My next step is to figure out the distributor problem and accumulate additional running time before adding the prop. I'm hesitant about adding the prop because I'm not comfortable with running the engine inside my shop with it installed. The engine is very heavy and is going to require a back-breaking effort to navigate it through my crowded shop and get it outside. I want to minimize the number of times I'll need to do it. I then plan to replace my wife's video with one in which the engine is running on all cylinders and with its prop.

The coolant leaks, though have really let the air out of my sails. Most of the engine will have to be torn down to properly address them. Frankly, I think chances are high that if I decide to do it, I will just move the leaks around instead of eliminating them. I'm also very concerned about separating the heads from the cylinder blocks without damaging either or both. I'll need to think more about this before deciding if it's the way I want to spend my winter.

In any event, I've taken a few photos of the final assembly as I don't expect the project's external appearance to change. But who knows? I made need them this winter. - Terry

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dairwin

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Excellent first run Terry. Seems readily willing to turn over and run despite the gear friction.

David
 

mayhugh1

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David,
Do you engines leak coolant?
Thanks
Terry
 

Ghosty

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Terry, Congrats on the running engine. There was no way this would not run, all the effort, checks and rechecks that you have done over the build.:thumbup::thumbup:

Cheers
Andrew
 

dairwin

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David,
Do you engines leak coolant?
Thanks
Terry
No. Oil yes. I would like to know more about the seals used in your engine, but the main area of coolant leakage in the Merlin is the seal between the bottom of the cylinders and the crankcase. There is a triple rubber seal (like 3 o-rings side by side) which provides the lower seal. Tope top seal is a barrel shaped brass connector with two o-rings.

I run my engines with 35 percent antifreeze (ally friendly type) and deionised water.

David
 

RonC9876

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Terry: Congratulations! What a mind blowing piece of work you have created! I could feel your nervousness as you powered everything up and hit the starter. Always scary starting a new engine especially one as complicated and work intensive as this one. So many things that can go wrong. But it has passed the test with flying colors. It runs! Maybe those coolant leaks are something you could get used to. Tearing this monster down would be a nightmare and as you said might be counterproductive. I have an oil leak on my Novi that showed up after my scavenge pump quit during a long run due to a stripped thread on the main bolt that drives it. I dread taking the engine apart and have been running it with a diaper underneath. I have tried all manner of ideas to stop this leak without taking the engine apart but it continues to drip. The worst part is that the source of the leak has remained hidden. It almost seems to be leaking through osmosis. I cannot pinpoint where it comes from. It bugs me to no end and a tear down is in the future for sure. It runs so well now and I am afraid that I might cause some other problem taking it apart. Torture!
 

ShopShoe

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Terry,

Congratulations.

I think I've read every post on this thread and looked at every picture. Every part of this build is phenomenal. You've met every obstacle and solved all the problems. All that is left is peanuts (or chicken feed, as the old-timers said). As others have said, this is a work of art.

The video shows it's a runner. I remember early in the project when you were talking about warped castings and etc. and suggesting that this might turn out to be a display. BUT IT RUNS.

I am convinced that you will resolve the unevenness and the leaks somehow and look forward to seeing how or what you decide.

For now, enjoy the success and take a breather.

I can't say congratulations enough times

--ShopShoe
 

cfellows

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Congratulations, Terry. Great to hear it running. I look forward to seeing the engine in person when you're ready to show it off!

Chuck
 

mayhugh1

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No. Oil yes. I would like to know more about the seals used in your engine, but the main area of coolant leakage in the Merlin is the seal between the bottom of the cylinders and the crankcase. There is a triple rubber seal (like 3 o-rings side by side) which provides the lower seal. Tope top seal is a barrel shaped brass connector with two o-rings.

I run my engines with 35 percent antifreeze (ally friendly type) and deionised water.

David
David,
The 28 top seals are short aluminum connectors each with a single o-ring. The 12 top liner seals are metal-to-metal press-fits. The 12 bottom liner seals each have a single o-ring which is sandwiched between between the liner and crankcase deck. All pretty much scaled down from the full-size engine. My leaks seem to be one or more of the top seals. The coolant has wicked throughout the entire gap between each head and cylinder block, and so it's difficult to pinpoint its location. Right now, I get about a teaspoon of coolant that drips out immediately after a run. If I wipe that up, nothing else seems to show up until the next run. I'm slowly making my peace with it.
I just hope I can resist adding some kind of snake oil sealer to the coolant. I used Barsleaks some 30 years ago in an old beater car I had, but I don't remember how well it worked. They have so many different types nowadays, but their website is very poor about explaining the differences between them. i expect my problem is rubber-to-metal, and I'm guessing those types of products are intended for metal-metal leaks. - Terry

p.s. I just remembered that I didn't answer your question about the return line from the carb bowl. When the pump is pumping it fills the carb bowl, and any excess fuel not used by the engine is pumped back into the tank. When the pump is shut-off, gravity will eventually empty the bowl back through the pump because the bowl is physically higher than the tank, it is vented, and the bowl's input line is at the very bottom of the bowl. Hope this answers your question. - Terry
 

DICKEYBIRD

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I just hope I can resist adding some kind of snake oil sealer to the coolant. I used Barsleaks some 30 years ago in an old beater car I had, but I don't remember how well it worked.
Congrats on finally tasting the sweet taste of success! I really admire your perseverance on finishing the engine itself and the documentation of the process.:thumbup: Like me, I'm sure everyone that's been watching this thread feels excitement every time you post an update.

If it makes you feel any better, as part of the regular scheduled maintenance antifreeze drain/refills on the Jaguar V-12's we service at the dealership, it is required by Jaguar that 2 "sticks" of Bars Leaks are installed along with the new antifreeze.:)
 

dairwin

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Hi Terry - I was just updating my earlier posting with more detail, but you seem familiar with the real set up (so I won't!).

The overall top fit of the liners and cylinder head (both early and late Merlin) is quite critical and not easy on the first attempt. The later two-piece heads involve some care regarding bending/flatness and accommodated by different torque setting of the end pair of nuts.

From earlier photos of your engine, it seems to have a two-piece head. The objective is to achieve the same compression on each liner, i.e., that the liner/head contact is at the same point such that the torque of the head nuts achieves a uniform compressive force. I am sure you will have paid great attention to this.

Assuming the above has been followed, any leak from the top is likely to be minor.

Given that you have mentioned a teaspoon of coolant, I would consider running the engine for a while and monitoring the coolant loss. You may find that the seal seating improves and the coolant loss reduces. I would consider this, before taking the heads off again.

I would not use any leak-stop fluid. Best to understand the source, even if it is not fixable. The reported leak rate is low at present and with time may seal completely. I would also resist using any non-water coolant. Just my opinion.

Thanks, re the pump return. The Merlin pump gearing provides a slow return of fuel through the pump. If an Amal pressure regulator is fitted, then there is no appreciable leak back and the engine can be restarted the next day without any line priming.

DAI
 

Rustkolector

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Terry,
Your Merlin has been, and continues to be absolutely the most awesome build I have ever seen. Congratulations!

However, as one who has seen a lot of real engine failures, your comments on coolant leaks reminded me of a model engine crankshaft I had to remake due to a head gasket failure and automotive ethylene glycol (EG) antifreeze mixing with crankcase oil. I have always had reservations about using ethylene glycol based antifreeze in my model engines, but I need it since I attend shows in the dead of winter. EG can be devastating to engine bearing journals when it mixes with engine oil. Unless you are absolutely convinced that a cooling system failure can never allow antifreeze to come in contact with your oil, I would look for another type of coolant that is anti-corrosive yet more oil friendly, even if it has little or no anti-freeze value. You can always drain it. I am sure you have considered this issue somewhere along this lengthy build, but I wanted to mention it just in case.
Jeff
 

Twizseven

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Having recently been in a Lancaster bomber on taxyruns the fantastic sound from the Merlins is replicated by your engine. Congratulations on a phenomenal build and the most comprehensive build documentation I have ever seen..
Colin
 

mayhugh1

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I seem to be plagued with a signature screw-up that has affected my last three engine builds including this one. Regardless of all my care and pre-testing, I continually manage to sabotage the distributors in such a way to cause the rotors or timing disks to lose crankshaft synch during the engines' very first runs. In the Quarter Scale's starboard-side distributor, a pinch bushing was machined a little short and allowed both the rotor and trigger disk to slip. In the 'first pop' video, the starboard cylinder bank started out firing very intermittently and then eventually not at all. The abrupt stop was caused by a jump in timing that created a backfire through the carburetor and a resultant stall - not a good thing for the supercharger gearing.

After machining a new bushing and re-timing the engine, it finally fires consistently on all twelve cylinders, and all the exhaust turnouts now heat up uniformly. The engine starts almost immediately with the electric starter and within five seconds or so using the slower drill starter. After tuning the carb, the throttle response is smooth up to about 3/4 full throttle which is as high as I've run the engine so far. The best performance seems to be with the Perry's high speed needle set open about 3/8 turn from fully closed. The tach wasn't initially working, and so I wasn't able to measure the actual engine speeds. As a reminder to myself to not blip the throttle and abuse the supercharger, I tightened up the lever in the quadrant throttle to make its action very stiff.

So far, the timing hasn't been changed from its initial 10 deg setting. I plan to wait until the prop is installed before experimenting with it since the load will likely affect the timing and probably the carb's settings as well.
I've managed to run about 25 ounces of fuel through the engine so far in a number of one minute runs. Although others have their favorite break-in procedures, I like to condition a new engine by temperature cycling it with a number of short runs separated by thorough cool-down periods.
With all cylinders now firing, the engine is considerably louder. The exhaust turnouts probably have something to do with this since the Merlin is considerably louder than my 18-cylinder radial.

After resolving the timing problem, I spent a couple days tending to a number of smaller issues. I replaced the high pressure oil gage which was damaged during the engine's very first start-up. The high pressure regulator wasn't yet properly set, and when oil pressure came up for the first time the 30 psi gage was pegged and left with a 7 lb. offset. Fortunately, I was able to replace the gage with an identical looking 60 psi model. I also re-adjusted the oil pressure regulators. I set the high pressure regulator to 40 psi which is the oil pressure seen by the crankshaft and rod bearings. The low pressure regulator was set to 20 psi. This is the oil pressure seen by the cams, the front drive, and the wheel case. I'm currently running the ceramic supercharger bearings dry except for any wheel case oil that finds it way into the bearings which I expect is non-zero.

The non-working tach was a puzzle since it had been thoroughly tested beforehand. I eventually discovered that the artwork used to mill the interface boards in the ignition modules left a bridge that degraded the tach driver outputs. The end mill used to remove the copper from the circuit boards had been too large to fit between an important pair of traces related to the tach output. The CAM software, whose prime directive is to not gouge legitimate part material, ignored that particular area of the board and left copper between two critical nodes. The ignitions themselves weren't affected, and since I used a hand-made driver breadboard to test the tach, I didn't catch the flaw in the circuit boards until now. Once located, though, the problems were easily corrected with an Xacto knife.

A Texas hurricane has brought rain into our area that will continue for much of next week. So, instead of a final outdoor video, I cleared an area on my workbench so my wife Mary could video the engine running with the prop installed. For this video, I bumped the timing up to 15 degrees and slowly varied its running speed between 1100 and 2000 rpm. The engine wants to rev higher, but its operator isn't quite ready. I'm not yet sure how low the engine will idle because the throttle is currently against the carb's idle stop at 1100 rpm. My custom carb mount makes any change to this stop a little less than straight forward, and so I need to go back and review my construction notes. - Terry


[ame]https://www.youtube.com/watch?v=0tOUQt5fem0[/ame]
 
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Ghosty

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Terry,
ABSOLUTELY BEAUTIFUL, is all I can say.th_wavwoohoo1
Don't worry about model of the month, it should be model of the year, decade, century.

Cheers
Andrew
 

Ken I

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Absolutely stunning - I'm dumbfounded at the craftsmanship and attention to detail - your documentation alone deserves outrageous praise.

Having followed this post since the get go I've been mesmerized every step of the way.

Don't worry about model of the month, it should be model of the year, decade, century.
Couldn't agree more.

Hall of Fame quality for sure.

Regards,
Ken
 
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