Quarter Scale Merlin V-12

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6 x 400 rpm = 2400ppm = 4800rpm for a single cylinder (one pulse per two revs).

To get 1600rpm it had to be a three cylinder. Or a 1 1/2 cylinder :D two stroke or redundant spark.

Puzzling.

Ken
 
The electrical panel will be the bottom-most panel to be installed at the rear of the running stand. It will support the throttle and tachometer as well as a panel voltmeter plus three or four toggle switches that will be used to control the engine's electrical functions. The fuel pump will be mounted to the front of the electrical panel, and so it will also contain a voltage controller for the pump motor. Due to their large physical size, the high current (80 amp) starter components will be mounted on a separate panel that will be bolted the starboard side of the stand near the starter motor.

The panel, itself, is made up of three parts: a front plate, a rear plate, and a mounting block for the tach. The front plate and meter mounting block were rough machined separately before being permanently joined together with Loctite'd screws. After joining, the pair was finish machined. The throttle and tach will be mounted to the front plate which is also pocketed to provide clearances for the voltmeter and panel switches that will be mounted to the rear plate. After assembly, these two plates will form a protective enclosure around the meter, the switches, and their wiring.

The tachometer will be shoehorned into the space above the throttle. The throttle control rod, which would have been difficult to relocate, barely clears the side of the tach. The narrow slot in the front plate through which the rod passes was just one of the reasons why the tach mounting block was machined separately from the front plate. The extremely long 1/8" end mill that would have been used to machine the slot in the thick front plate while clearing the meter block would have chattered badly while literally chewing through the slot. The other reason, though, was that I didn't have a suitable block of aluminum to create them as a single part.

Before machining the rear plate, I performed a trial assembly of the front plate, tach, and the throttle. This was probably just one of several trial fits to come. The entire panel assembly would have been a good candidate for modeling before doing any machining. But, since a lot models would have had to be created for the non-machined parts, I decided to just fit things as I go. I don't normally like working this way, but my process standards seem to be yet another thing that's shriveling with old age.

Two of our grandkids are coming for a week long visit, and I don't plan to do much more on the build while they're here unless it's to sneak in a few late-night-can't-sleep hours. Anyway, it's probably a good time, while there's still a lot of space left, to step back and make sure that something important isn't being left out. - Terry

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Kvom,
I've been experimenting with the three flute roughers in aluminum for a while now. They seem to be quieter for the same metal removal rate compared with a two flute cylindrical cutter, but I haven't made my mind up about them yet. They're trickier to use without flood cooling since the flutes tend to load up in aluminum, but I can still get maybe 50% greater removal rate with them. - Terry
 
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Before doing much more that might complicate its installation, I added the drip pan originalły planned for the stand underneath the engine. A box brake was used to form a shallow five-sided tray from 16 gauge steel, and its corners were tig-welded closed. After painting the tray with Rustoleum texture paint, it was attached to the cross supports on the floor of the stand. I've used this particular paint in model engine builds before (most recently, the Merlin's rotisserie assembly stand) because it's inexpensive and resistant to most engine fluids after being allowed to air dry for three or four days. The 'multicolor' version easily covers up significant surface defects (ugly welds, deep scratches, panel beating marks, etc.) with a thick, durable, and remarkably uniform looking finish.

I also finally completed the coolant loop between the radiator and the return inlets on the coolant reservoir. Even after a lot of thought, I wasn't able to come up with a drain **** that looked at home under the engine, and so I scrapped the idea completely. Instead, I'll just disconnect the return hoses from the coolant reservoir when the system needs to be drained. I machined three sets of spreader bars for the hoses, though, in order to tidy up their routing.

For completeness, I finished up the wiring for the electric starter even though all the work that I've put into the engine's starting system may have been for naught. John Ramm (the only builder I'm aware of to get a running engine completed from these castings) recently informed me that the steel bevel gears in his Merlin's starting system had a very short life that seemed to come to an abrupt end just after his engine's rings seated and cylinder pressures rose. This is why you'll see him slap-starting the prop in his Youtube video. I've had major misgivings about the robustness of the starting system design ever since coming to grips with the incredible complexity inside the wheel case. I took great pains in setting up the starter gears during the wheel case construction, and my modifications to the geometry of the cylinders effectively lowered the static compression ratio about a point and a half. I guess my starter's durability remains to be seen.

I mounted the starter components on a hand-formed sheet metal panel mounted to the starboard side of the engine just below the starter motor. Ten gage 'noodle' wire was used for the high current wiring. 'Noodle' wire is something I recently discovered in a local hobby store. It's an ultra-flexible silicone insulated wire, and in this particular gage it has an impressive 1050 strand count. For the starter solenoid I used a 120 amp SPST automotive accessory relay that I found in a local auto supply store. The starter switch is a red-cover momentary toggle reminiscent of the P-51's original starter switch.

A pair of 6 mm hex binding posts for the 12 volt battery input were mounted in a terminal block machined from black Delrin. Both the starter motor and the rear electrical panel will receive their power from these posts. Hopefully, the short term current carrying capability of these posts and their associated wiring will be adequate to handle the engine's 80 amp starting current requirement. Troughs were milled into rear of the block to accommodate the huge wire. Metal inserts were pressed into the block's machined barrier terminals to handle the connections running off the starter panel.

The starter panel was designed to be a standalone sub-assembly. The 12 volt power cable from the radiator fans was terminated on the starter panel but will be continued to a control switch that will be mounted on the electrical panel at the rear of the stand. The fan cable as well as the 12 volt power feed for the electrical panel will continue from the terminal block to the electrical panel through quick connect blade terminals on its rear side.

The remainder of the noodle wire was used to make up a pair of battery cables. Since I had taken liberties with the current carrying capabilities of several of the starter components, I energized the starter motor several times while checking the various connections for excessive temperature rises.

The next step will be to finish up the rear electrical panel. - Terry

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That coolant looked interesting so I had a brief look at the specs which were a little surprising. The manufacturer gives the specific heat capacity figures at 90 C (and I think it's safe to assume they chose this temp because that's where they get the the highest figure) of only 2.633 J/g.K. This is a far cry from the SHC of water at 4.186 J/g.K. For that don't know, specific heat capacity is the amount of energy (heat) that one gram of water absorbs to increase in temp by one degree (celsius or Kelvin). So this 'coolant' will only absorb 2.633/4.186 * 100 = 62.9% of the amount of heat as the same amount of water, for the same increase in temperature. Also very interestingly, the coolant has a flash point of a mere 120 C (the point at which it gives off enough vapour to ignite in air) which is far less than it's boiling point of 191 C. To top it off, despite being marketed due to it's waterless qualities, it is hygroscopic and will absorb water if exposed to the atmosphere (like in a coolant header tank).

So to summarise, it may catch fire if the cooling system overpressurises, the cooling system is likely to overpressurise as its efficiency is only around 63% that at which is was designed to be when operated with water as coolant, and it's likely to contain water soon after you install it. Personally, there's no way I would be running this stuff in any vehicle(or model) of mine.
 
I doubt the flash point issue is a concern is reality since there shouldn't be any air other than at the top of the radiator, and no spark there to ignite it. The peak operating temperature of the engine would determine if there is any concern. The obvious advantage is not needing to drain the system to prevent corrosion. The specific heat capacity is lower but since it boils at a much higher temp than water the total cooling capacity may be greater or equal assuming that the engine can withstand coolant that much hotter. No boiling means no pressure rise or boilovers.

An interesting option. I may be interested in using this in my offroad Jeep, which has an issue with overheating on hot days. It actually has two smallish radiators and a 6.0 V8. I have to remember to turn on the rear fan manually when the temp gauge goes too high. $45/gallon isn't cheap, but if it never boils over or leaks it should last a long time.
 
I'd have to disagree on a couple of points. With the liquid experiencing a larger change in temperature (with the higher boiling point to account for the SHC change) there is more thermal expansion and that extra volume has to go somewhere - ie into a header tank, or vented to atmosphere, neither of which are sealed and therefore exposed vapour occurs. Of course it is susceptible to water absorbtion at this point in the header tank also. The bigger deal with running with a higher coolant temperature is the higher temp of the components the coolant is supposed to keep cool. With the engine running over design temp I'd imagine all sorts of problems to arise with things like fuel vapourisation within lines and stability of some materials like plastics, hoses, manifold fittings and even bearings (for example, most general rolling bearings have an upper temperature limit of less than 150 C,maybe less, above which they will permanently deform and will not return to correct shape upon cooling). So I don't believe the increased boiling point is much/any benefit and I suspect your Jeep will have worse overheating problems. Of course I could be wrong and I'd be interested in seeing the results of a trial if anyone does try it out.
 
The literature states that the hottest area of an engine is right around the cylinders (makes sense). And there the temperatures can cause water to flash to steam. Steam has no capacity to absorb more heat, plus can cause pitting over time. If that does in fact happen then the specific heat capacity would be reduced over the theoretical value.

I'm going to ask some mechanics I trust about it. A vehicle might need a higher reading temp gauge and some changes in the computer to avoid going into limp mode.
 
Just had another thought and checked the specific heat capacity of antifreeze solutions. 50% ethylene glycol lowers it into the mid 3s. Of course the Merlin probably doesn't need antifreeze.
 
That is exactly the reason why a coolant system is pressurised nowadays .
To raise the boiling temp and thus avoid the flash steam problem .

I just did an engine rebuild , and long story short , I had a faulty radiator cap .
The system remained at atmosferic pressure and as soon as the engine was shut off
it started to boil .

As far as I know , water has one of the highest thermal capacity and is by far the best choice for cooling . Just needs some anti corrrosion and antifreeze additions . But mostly it's simple plain water .

This offcourse is my ecperiance with cars , not models .

Pat
 
The literature states that the hottest area of an engine is right around the cylinders (makes sense). And there the temperatures can cause water to flash to steam. Steam has no capacity to absorb more heat, plus can cause pitting over time. If that does in fact happen then the specific heat capacity would be reduced over the theoretical value.

I'm going to ask some mechanics I trust about it. A vehicle might need a higher reading temp gauge and some changes in the computer to avoid going into limp mode.

No, steam does have the capacity to absorb more heat or we would not have super-heated steam systems such as locomotives and nuclear submarines.

BTW, Barry Hares in Birmingham built the first Merlin V-12 if I remember correctly. Several others have built running Merlins as well. Some from casting kits and others from bar stock.

Here is a YouTube video of it: [ame]https://www.youtube.com/watch?v=0xe1LL1IC7Y[/ame]
 
After some research on the Evans product, I think it's probably not for me in the Jeep, and probably not for the Merlin. Here's a test a competitor product ran: http://www.norosion.com/evanstest.htm

The competitor (No-Rosion) may make sense as adding it to water may eliminate the need to drain the cooling system. I also found this article about the proper type of water to use in an engine where corrosion is an issue (esp. aluminum). I'm now thinking HyperKuhl with straight water for my Jeep.

http://www.onallcylinders.com/2016/09/09/coolant-additive-guide/

An interesting sideline to this build regardless.
 
Having had many years of experience in the motor repair industry, One of the main reasons of overheating in high revving engines, make that water pumps, is that at higher revs, cavitation can take place with poor design of impellers. Sharp edges at the tip of the impeller should be avoided. Norm
 
Interesting post, regarding the non water coolants. I was invited to consider using this product in my Merlin. (Cooling of the real engine can be a problem for prolonged ground running). I looked at the specs for this material, but decided to concentrate on improving conventional cooling with improvements to the radiator air flow, fitting an effective cowling, and changing settings on the propeller. I also added cooling fans on the backside of the coolant/oil cooler block to achieve prolonged running temperatures.
 
Maybe it's just me, but I've got nothing but a black box where the YouTube connection is supposed to be.

Link broke?

Don

It's not just you, it's a weird issue with the forum software and Internet Explorer currently. Until it's fixed, using some other browser will allow you to see the videos.
 
It's not just you, it's a weird issue with the forum software and Internet Explorer currently. Until it's fixed, using some other browser will allow you to see the videos.

Yup, opened up in Chrome & the embedded video displays & runs perfectly vs. black screen in IE. I just went through a similar IE rigmarole on another forum with sporadic picture displays. Hope the issue gets resolved.

Anyway, as usual, beautiful workmanship!!!!
 

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