Quarter Scale Merlin V-12

Help Support HMEM:

V22

Active Member
Joined
Aug 16, 2013
Messages
40
Reaction score
6
If only Terry could somehow get this content into a book. I would be the first to place an order. The content here is truly astonishing. This should really be preserved.
 

mayhugh1

Project of the Month Winner!!!
Project of the Month Winner
HMEM Supporter
Joined
Oct 24, 2007
Messages
957
Reaction score
2,816
Location
Central Texas
Terry
I did not follow when the storms were going on, was your place alright with all the bad weather?
Very impressed
Nelson
Nelson,
Thanks for asking. Here in central Texas we got only a bit of wind and about 6 inches of rain from Harvey. If it hadn't been for a high pressure area that had settled over us, the story might have been a lot different. - Terry
 

RonC9876

Well-Known Member
Joined
Jan 17, 2011
Messages
67
Reaction score
8
Terry: I can't imagine how you survived the week away from your engine just itching to find out what had happened and fixing the problem. I would bet that it was hard to sleep during that time. Glad that the problem was relatively minor and was easily fixed. All the things that could have happened had to be working over your mind and body. Take care and here is hoping that nothing like that happens again.
 

mayhugh1

Project of the Month Winner!!!
Project of the Month Winner
HMEM Supporter
Joined
Oct 24, 2007
Messages
957
Reaction score
2,816
Location
Central Texas
I thought I'd pass along some observations to those with their own sets of castings, based upon my experiences with the running engine during the past several week.

The average fuel consumption turned out to be about an ounce of gasoline per minute, and so the ten ounce fuel tank that I used is a reasonable size. The engine now has about 1-1/2 hours of running time on it, and has burned nearly three quarts of 92 octane gasoline (Truefuel).

The heads warm up to 180F in about 30 seconds (consistent measurements made along the exteriors of both heads), and they've remained there during the 2 minute runs that I've made so far. The coolant pump circulates an impressive amount of coolant, and the temperature of the rear reservoir housing has reached 150F during the longer runs. So far, all the running has taken place inside my shop, and I haven't tried to extend them because of fumes. With the current radiator and reservoir sizes, though, I wouldn't feel comfortable with running any longer than a couple minutes. The cooling issues I'm seeing would certainly limit the engine's use in a flying scale model which was one of Dynamotive's original visions. The engine starts easily when cold but sometimes labors the starter when hot.

There's a lot of heat in the prop wash, but it's mostly exhaust heat. I generally allow the radiator fans to run several seconds after the engine has been shut down, mainly to give some purpose to the otherwise useless fan switch that I installed. The fans, of course, remove heat only from the coolant in the radiator since there's no circulation when the engine isn't running.

The engine doesn't blow smoke or oil out through its exhaust, and so the rear of the stand stays much cleaner than I had expected. Water, which is a normal byproduct of combustion however, collects inside the sooty exhaust tips during the first 30 seconds or so of running until the engine temperature rises enough to vaporize it. This is a common occurrence in automobile tailpipes while the engines are warming up. A bit of this soot collects on the two rearmost exhaust tips as well as the top covers of the distributors.

The Perry 9400 carb seems well matched to the engine and performs well with gasoline. I ended up with the high speed needle open between 3/8t and 1/2t from its fully closed position. The carb's mixture disk didn't have to be changed to accommodate gas and is still sitting at its stock neutral setting. The engine starts easily in the shop's 70F - 80F ambient, and so far, choking hasn't been necessary. This will probably change when the shop's temperature drops 20F this winter. Starting is consistent so long as the previous run was terminated by shutting off the fuel pump so the engine was forced to run out of fuel. If not, gasoline settles inside the enormous intake and drains down through the supercharger's long vertical input where it soaks the carb, puddles in the drip tray, and leaves an overly rich condition for a restart. Shutting the engine down in this manner also tends to clean up any rich-running plugs.

The engine accelerates smoothly with a fixed timing of 20 deg BTDC. Performance seems relatively insensitive to any timing between 10 and 25 degrees.

After all was said and done, I still have some coolant leakage. About a teaspoon of coolant collects in the drip tray every day or so - just enough to be irritating. I expected and was prepared to tolerate some oil seepage, but leaking coolant is a different matter. After punching some trial and error pinholes in the bottoms of a number of paper cups, I was able to experimentally determine that the leak is roughly equivalent to a .020" diameter hole. I had been suspicious of the coolant seals, but now I believe there is yet another porosity issue with one of the castings. The leak is small enough, though, that I can't even be sure on which side of the engine it's on, but fortunately there's no sign of it in the oil.

I repaired two starboard head porosity leaks that I discovered when pressure testing the heads last winter just after assembling them to the blocks. My guess is that this leak is probably in the same casting, and my original setup wasn't sensitive enough to show it. Porosity issues are ideal candidates for a number of stop-leak sealants, though, and I'm currently experimenting with some solutions. If I were willing to wait several more months, investment that's probably still hiding in some of the coolant passages might begin circulating and plug it.

I removed the front drive cover to make sure the previously Loctite'd screws holding the large driven gear to its shaft were still in place. This time I noticed that the 1/4-28 bolt in the nose of the crank that secures the drive gear to the front of the crankshaft had loosened up. Since the drive gear is keyed to the crankshaft, I wasn't expecting a problem with this particular bolt. But, while I was in there, I blue Loctite'd it as well. For being one of the simpler portions of this engine, the front drive has been the source of a number of unexpected problems. The forces associated with driving the engine's huge prop evidently deserved more attention than I initially gave them.

The electric starter has been a great convenience, and so far the starting system has held up well. It now must be close to having accumulated a hundred start cycles including the initial testing it endured. The starter motor and battery that I ended up with turned out to be a fortuitous combination. They provide enough torque to quickly start the engine but not so much so as to break things when faced with a prop blockage.

The starter, along with the front drive, seem to confirm something that I continue to see on every complex project I'm involved with. The things that tend to give the most trouble are those that don't receive their share of worry. - Terry
 

dairwin

Member
Joined
Aug 2, 2017
Messages
21
Reaction score
10
Continued good luck with the engine Terry. More videos when you can!

David
 

tornitore45

Well-Known Member
HMEM Lifetime Supporter
Joined
Jan 17, 2009
Messages
895
Reaction score
153
The things that tend to give the most trouble are those that don't receive their share of worry. - Terry
After a lifetime of design engineering I can say this quote should be repeated at the introduction of any engineering course or text.
 

Ken I

Project of the Month Winner!!!
Project of the Month Winner
Joined
Oct 31, 2010
Messages
1,422
Reaction score
156
Location
Cape Town, South Africa
Terry,
I have built a number of pressure decay leaktesters for the automotive industry for both engine blocks and cylinder heads.

A finish machined head or block is typically permitted 5cc per minute (air leak) from the coolant galleries and 1cc per minute from the oil galleries under 5 Bar test pressure.

This seems to be the generally accepted level at which porosity type leaks will generally self heal.

Unfortunately they don't always self heal and we had one head come back from VW that passed test and when tightly tested was found to be pretty much exactly 1cc per min @ 5 bar and never self healed but this seems a rarity.

Problem - you cannot measure zero so some allowance needs be made.

Another routine the industry follows is to test the raw castings prior to machining(so as not to waste valuable machining on "scrap) and 10cc is the pass limit for further machining and anything over 100 is scrapped. Castings falling between 10 and 100 are parked outside for 3 months to "weather" - most pass on retesting after "weathering".

I don't think I would sweat the coolant leak - keep an eye on it - as long as it continues to diminish then it will probably self-heal - if not then go the Barsleaks method or similar - I have found this works best if you use the Barsleaks with water only - no other additives or glycol which seem to inhibit the self-healing process.

Regards, Ken
 

Cogsy

Well-Known Member
Staff member
Global Moderator
Joined
Jul 30, 2012
Messages
2,788
Reaction score
814
Location
Perth, Western Australia
I'm going to throw this out there, just so you have it for reference. On full-sized equipment with smallish coolant leaks (although nowhere near as small as yours is) adding a portion of ground black pepper (finely ground, 'dusty' stuff that makes you sneeze when you put it on your eggs, not chunky pieces) will generally solve the issue. I guess in the same way as your pieces of investment would 'fill the hole', the pepper clogs the leak. One advantage of the pepper as opposed to chemical additives is that it is completely inert and won't damage anything else it comes in contact with, and a coolant flush will get rid of any excess.

As for chemical additives, I have successfully used 'Stop Leak' which is a brand available down here as a clear liquid with fine particles of copper in it. It's basically liquid glass which sets in the hole (somehow, maybe magic). The big drawback is the heat needed to set the chemicals. Typically they need 30 minutes of engine operation at running temperature to activate, which obviously you can't do. Again not a problem you're likely to encounter, but I once used a chemical solution on an old 4cyl Nissan/Datsun engine with a slight head gasket leak. It fixed the gasket but basically welded the rings into the piston on the leaky cylinder. I went from using 1/2 a litre of water a week to 1/2 a litre of oil instead.

I'm sure you'll get it sorted. I second the call for more videos of this mighty beast too!
 

ICEpeter

Well-Known Member
Joined
Feb 27, 2010
Messages
137
Reaction score
60
Hello Terry,
I am not sure how applicable this method could be without dismantling all or parts of your engine to solve your coolant leaking problem but I solved my radiator leaking problem using a Loctite anaerobic product (Loctite 648 retaining compound) by forcing the compound through the fissures in the radiator under 60 PSIG and managed to seal the radiator completely, holding up to 60 PSIG air pressure after without any leakage.
In the casting industry they use the same process to seal porosity in castings prior to machining and sealants for that purpose are available in larger quantities but not in the open market. It seems these sealants can only be obtained form the actual user (A foundry) in smaller quantities.
http://loctite.ph/php/content_data/LT1244_TT_Automotive_Porosity_Sealing_By_Design.pdf

Peter
 
Last edited:

mayhugh1

Project of the Month Winner!!!
Project of the Month Winner
HMEM Supporter
Joined
Oct 24, 2007
Messages
957
Reaction score
2,816
Location
Central Texas
I've used stop-leak sealers with mixed results in the old beater cars that I owned when I was much younger and poorer. Even with what little I knew at the time, something just didn't feel right about pouring thick brown sludge from a yellow plastic container into the radiator of the only car I had and depended upon.

If you visit today's online automotive forums you'll find many questions about whether these products actually work. Lots of 'experts' respond positively, and an equal number swear they'll cause immediate self-destruction of an engine. The truth is somewhere in between because there are different kinds of leaks and different kinds of stop-leak products.

The most difficult (practically impossible) leaks to fix for any significant amount of time are head gasket leaks, large radiator holes, burst hoses, and leaking water pump seals. Stop-leak products containing long fibers and/or sodium silicate (water glass) may help long enough in the first two cases so one can return home from a trip and make a proper mechanical repair. The only thing they can do for a leaking water pump seal is to clog up its weep hole so the problem is out of sight for a while. And nothing, except maybe a silicone tape wrap, is going to even temporarily repair a burst hose.

Candidates for long term repairs, though, are casting porosity problems and some freeze plug leaks. General Motors, in the nineties, routinely added their own stop-leak product to the coolant in a number of models as they came off the assembly line. GM had issues with casting porosity, and they hadn't yet learned to reliably seal aluminum heads to cast iron blocks. Their ACDelco coolant sealing tablets are still available and continue to be used today by some shops when performing flushes and coolant changes on these older cars. GM eventually terminated their use in new vehicles after developing their long-life DexCool coolant because their sealant tended to shorten the life of their new coolant's anti-corrosion package. Once dissolved in coolant, the tiny organic particles from these tablets continually circulate throughout the engine. The material (ground up walnut shells and ginger root) tends to find its way into small defects and seals them for pretty much the life of the coolant. When time comes for a coolant change, the engine is flushed, and new tablets are added to the new coolant.

These problems weren't limited to U.S. auto manufacturers. The 1990 Jaguar XJ-S Driver's Handbook (page 176) recommends adding two 135 ml bottles of Jaguar Radiator Leak Sealer to the vehicle's radiator after every coolant change, probably for the very same reasons.

This brings me to the Quarter Scale whose coolant leak I have good reason to believe is due to a porosity problem in one of the block or head castings. I researched the stop-leak products currently available so I could make an informed decision before irreversibly dumping someone's snake oil to the Merlin's coolant system.

I decided early on to avoid the common silicate-laden products because of my fear of the glass particles eroding the numerous tiny o-ring seals in the engine. As an aside, coolants themselves, unless labeled 'silicate free', may contain their own silicates whose purpose is to scrub the walls of the engine's coolant passages. The owner's manual for my Honda Valkyrie specifically warns that silicate-free coolant must be used or the water pump's factory warranty will be voided.

The second group of sealants that I eliminated from consideration were the products containing copper flakes. Although the manufacturers of these products claim they can be safely used in engines with aluminum heads and radiators, this doesn't make a lot of sense to me. I was careful to use only aluminum and stainless steel materials in the Quarter Scale's coolant system in order to avoid issues with galvanic corrosion. Using a stop-leak product that stuffs copper particles into a hole in an aluminum head in the presence of an eventual electrolyte would seem to guarantee that the hole will eventually grow larger. In addition, I didn't like the idea of continually circulating metal particles past the seals in the Quarter Scale, and especially around the one in its tiny water pump. So, I eliminated the aluminum particle sealers as well. I also crossed off my list the sludgy-looking fibrous sealers, just because. And so at this point I had eliminated all the stop-leak products available at my local auto parts stores.

The two products that I did consider had to be ordered online. The first was claimed by its marketing to be a polymer only product. It's a (very) expensive product sold under the name Titan Block Stop Leak on the Titan Sealer website and also under the name Dura-Seal Engine Block Sealer on the Dura-Seal website. Curiously, both websites look very similar and have exactly the same contact information. The second product was the inexpensive ACDelco sealant tablets described earlier. These are available through Amazon as well as several other online sources.

My own testing included the inspection of the sealers under a microscope after samples had been mixed in their proper proportions with coolant. I wanted to be sure that most of the particles were small enough to seal a .020" hole, and that there were an insignificant number that might be large enough to block the tiny coolant tubes in the Quarter Scale's radiators. Both sealants passed this test.

Next, I measured the time it took for a 100ml mixed sample to plug a leaking paper cup whose bottom had been perforated with five .060" holes. Both products plugged the leaks rather quickly - less than 10 seconds for the Titan Sealer and about 30 seconds for the ACDelco Sealer.

The last comparison was to allow the mixed samples of each sealant to sit undisturbed overnight in a clear container. The Titan product contains thousands of tiny polymer flakes in a thick carrier that isn't miscible in the coolant. This carrier hardens when exposed to air, and its likely purpose is to not only cement the flakes inside large defects but also to fill pinholes that are too small for the flakes. It's important that this particular product settles beneath the coolant in the bottom of an engine when it's shut off and away from any possible air pockets. After sitting for only several minutes, the Titan sealer separated out from the coolant and into a coagulant at the bottom of the container. The fine polymer particles appear to remain in suspension in the goo.

The coolant itself is the carrier for the particles from the dissolved ACDelco tablets. These particles remained in solution in the coolant, also near the bottom of the container, but quickly spread throughout the coolant when lightly agitated. There was no evidence of a goo or sludge that was reminiscent of some of the sealants I've used in the past.

In the end, I chose to use the tablets over the Titan sealer for a couple reasons. The goo bothered me because it would tend to settle at the bottom of the coolant system, and in my case that would be inside the water pump. I was concerned that during long storage periods the goo might thicken and cause the tiny pump to seize. In addition, adding the Titan sealer to the Merlin's coolant system felt like a somewhat irreversible decision. If I later changed my mind and wanted to remove it from the engine, I'd have to work quickly to remove it before the carrier had a chance to air harden.

Since there is about 1-1/4 liters of coolant in my particular Merlin, I dissolved 3/8 of a tablet in about 200 ml of coolant before adding the mixture to the coolant reservoir. This dosage followed the manufacturer's recommendations. I immediately ran the engine for a minute or so to circulate the material. After a cool down period, I made another one minute run after which there was no more sign of leakage. It's now been over two weeks with considerable run time on the engine and the seal is still intact. - Terry

1512.JPG


1513.JPG


1514.jpg


1515.jpg


1516.JPG


1517.JPG


1518.JPG


1519.JPG


1520.JPG
 
Last edited:

10K Pete

Well-Known Member
Joined
Jan 24, 2009
Messages
543
Reaction score
121
The only coolant system sealer I've ever used was "Alum-a-seal" which is a finely divided aluminum powder, nothing else. It never failed to stop the leak and never fouled a coolant system. I, and a half a dozen mechanics I've known, swear by the stuff. My Dad introduced me to it back around 1960. He'd been using it since air was new.

I may still have a tube of it somewhere....

But here it is..

https://www.goldeagle.com/product/alumaseal-radiator-stop-leak-powder

I've seen all the others clog, fail and otherwise make a mess...

Pete
 

bazmak

BAZMAK
HMEM Supporter
Joined
Dec 12, 2012
Messages
2,181
Reaction score
1,201
This thread and Buchanans clock are my favourite builds.Simply because
they so far ahead of most projects and way beyond both me and many others
No disrespect to others but these two posts in particular bring to most model
engineers the heights to which mere mortals can go
 

kvom

Administrator
Staff member
Administrator
Global Moderator
Joined
Jun 4, 2008
Messages
3,177
Reaction score
593
I'd add George Britnell to the list of people who's posts I always read.
 

10K Pete

Well-Known Member
Joined
Jan 24, 2009
Messages
543
Reaction score
121
I must agree. This is the sort of heady stuff that keeps this mere mortal inspired...

Pete
 

Ardent

New Member
Joined
Jan 27, 2018
Messages
2
Reaction score
0
If anyone knows of a set of these castings that is for sale, or may become so, please let me know. I realize what they’re worth and simply waited too long to order from the 1/4 scale site, the email is no longer active there, tried to contact to see about any remainders.

This thread has been better than any book I could have packed to camp. I’m flying helicopters in a remote work camp sixty degrees north and there are some long nights this time of year. Was very much appreciated.
 
2

Latest posts

Top