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PostPosted: October 17, 2014, 12:26 am 
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On the Crankshaft, while experimenting and researching the results, I ran across an interesting crankshaft design by Maybach, which combined the web with the bearing load structure, a disk web. While Maybach used this to shorten the length of the engine, the other advantage is that you can build with more margin, using roller bearings, while strengthening up the engine block itself. No need to cut the crankshaft tunnel in half. Also each web would act as a mini flywheel to help reduce vibration as well as can be expected from 102mm wide disks. Several motorcycles use this approach to good effect. Being a built-up crankshaft, every bit that can be bought as margin is to its advantage. So far, the test setup has held up remarkably well. It would also shrink the overall length as well. I destroyed enough testing elements at this point to have a good idea of what margin I can get away with, but I'm still being cautious. While the picture here uses needle bearings, great if you have the skill to make, I was planning on using 1/2" ball bearings, two rows in a groove on the disk, with a screw-in cover within the engine block itself on each side to hold them in. Would also hold the crankcase in place as well. In theory, of course. The problem is, the size puts a lot more stress on the bearings. Checking around, it is difficult to find commercial bearings which can even handle the anticipated RPM's. Which explains why Maybach used these on diesel engines, with far lower RPM's.

The idea of using a disk as a mini-flywheel however is still something I'd like to take a look into.


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PostPosted: October 21, 2014, 11:47 am 
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Alright, finished up the mask concept for the web. Thanks to having designed the case to handle a crankshaft of up to 180mm I have the room for my counterweight solution. The actual crank web disk will be a 25mm thick steel plate with one hole drilled for the 45mm/ crank pin which will be kept in place by having a screw-in large-nut on each side, a similar hole for the 55mm bearing rod, and three bolt-holes on the side opposite of the crank pin's for the addition of a bolt-on counterweight. The goal is to make the disk balance along the centerline, so these holes will need to be cut to result in the same weight being removed on both halves of the center. And by bolting it on the outside of the web, it does not require significant width addition.


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PostPosted: October 21, 2014, 2:02 pm 
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Transmission gears. The plan is to use double ANSI 40 chains over the following sprocket sizes:

Gear 1: 13 tooth to 38 tooth - ratio 2.92
Gear 2: 18 tooth to 35 tooth - ratio 1.94
Gear 3: 21 tooth to 30 tooth - ratio 1.43
Gear 4: 22 tooth to 26 tooth - ratio 1.18

Each gear would have a 9-tooth freewheel gear on a spring-loaded swing arm tensioner to keep it tight . For this I planned on including a sensor that, should the arm ever close (from a chain breaking) it would send out a signal to tell the driver which chain just failed.

Alternatively it could use a single ANSI 60 chain. The main reasoning for the double ANSI 40 was to buy redundancy and the double 60 was too wide for the rest of the system.

Reverse will use a 4-pitch gear setup:
Reverse : 48mm 12 teeth to 180mm 45 teeth - ratio 3.75

An overdrive system could be added later on, but not planning on it at this time.

Funny bit is, the reverse gear will cost more than all of the sprockets put together.


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PostPosted: October 24, 2014, 12:01 pm 
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For fuel delivery, I am of two minds:

1) a classic carburetor is well proven in DIY applications. I happen to have a spare Holley 5740 for this use, and I will likely use it for initial testing of the new design. The original Carter I was using finally gave up the ghost when I overheated the block and split its casing.

2) The past few decades of development has made DIY EFI not only practical, but quite affordable. Using the open source Megasquirt ECU, off the shelf injectors, sensors, coil-on-plugs, it likely would be better over the long term. Easier to get information, easier to tune, less mechanical parts to fail, etc.

What are everyones thoughts?


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PostPosted: October 24, 2014, 9:16 pm 
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Location: West Chicago,IL
Check out our Megasquirt thread.[url] viewtopic.php?f=27&t=12117
[/url]

Several of us have been successful implementing the MS system(s) Mine is a generic MSII with no additional modules. The Megasquirt capabilities are ever growing. This is the ONLY car that I have ever had to tune, either with a carb or with EFI. Once the initial cost is spent, any tuning is done quickly and cleanly. No extra costs are involved for main jets or emulsion tubes. Just sit at your computer and press a few buttons.

I am a fan of the MS, but the startup has a steep curve for somebody with no prior experience. For a DIY engine, I can think of nothing better than a DIY fuel/ignition system like the MS.

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Visit my ongoing MGB Rustoration log: over HERE

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PostPosted: October 25, 2014, 1:45 am 
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Location: Under the weather. (Seattle)
Granted, I have yet to try my hand at DIY EFI, but I have little love for carbs...So I would probably try the Megasquirt route.

I like the crankshaft concept. I have thought a lot about ways to do assembled crankshafts as well, and have not come up with many that I would feel comfortable putting in an engine. That one does solve some of the problems. My main concern would be bearing cost and longevity from the repetitive impact loading on the rolling element bearings. I wonder how big of an engine it would have to be to have main bearings that large.

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PostPosted: October 25, 2014, 4:52 am 
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Roller bearings were used in Formula 1 racing for awhile during the V10 era, I've been reading papers on some of the results for awhile. Also the Bugatti Type 35 used a very similar crank design. The key they found in Formula 1 was to use a high-pressure dry sump oil system, and the Bugatti's oil system was quite overkill for what was expected in the era as well. This I was planning on a high pressure dry sump anyways for other reasons, such as the piston rod lubrication delivery system.

But, it is an experiment anyways. I still can go back to the original journal design if it does not work out..


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PostPosted: October 26, 2014, 1:24 pm 
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I find Tatras' solution really neat. If you are really into build-up crankshaft, try searching for Hirth joints and aircraft cranks..

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PostPosted: October 29, 2014, 4:01 pm 
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I have the devil's luck it seems. Friend of mine pointed me to a crank (he had no idea what it was out of) using hirth joints. Incredibly easy to adapt them to fit the model I was working on, and with a bit of work got my 3D mapping software to lay out how to grind one/print one. Need to get off my ass and finish building the new printer however.


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PostPosted: October 29, 2014, 8:01 pm 
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My friend also pointed me at a Toronado and its HyPo chain drive. Checking around, turned out that HyPo sprockets and chain are less expensive than the ANSI 40-2 I had been looking at. Causes an issue with the sprocket sizes however, as I can't get the tooth count I had been wanting. But, checking around.


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PostPosted: October 30, 2014, 12:05 pm 
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After a lot of deliberating, wife and I decided on letting go of the Mountaineer. Once we realized that, should I replace the transmission, the computer would freak out. And if the computer freaks out, it would not pass emissions testing, the writing was on the wall. But, now I'll have garage space to work.

Or not, the state let me know that they'll list the truck to use tailpipe testing.

Ok, talk about 11th hour reprieve. Also found out that the transmission issue may just be a bad 2-3 accumulator spring.


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PostPosted: November 3, 2014, 12:35 pm 
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I realized, in the discussion of the heads, it was never mentioned how it could keep the profile low:

The intake design is modeled on that of the Slant-6. Intake, and Exhaust, come in on the same side. because the cylinders are longer than is usual, there is plenty of room to run the exhaust over the top of the engine, under the intake manifold. This narrows the engine to fit into the engine bay w/o worry, and with the cam on the side of the valves and not the top, it should lower it enough that it should fit under any Locost-7 hood.

*edit* Found out that BMW made a version of its 4.4L engine with a similar configuration, which they called a reverse-flow exhaust. They use it to run a pair of turbochargers in a very compact space.


Last edited by Downix on November 5, 2014, 3:08 pm, edited 1 time in total.

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PostPosted: November 3, 2014, 7:29 pm 
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Getting into the more concerning areas, and the desire to avoid a Vega-like situation, since I already cracked one test cycle trying it, I'm working to make sure that the aluminum block has some breathing room around the cylinder mounts. In effect, the cylinder mounts will have a slightly oval shape to them, to allow the underlying block some room to breathe as it were. Otherwise, as I found out, you can crack the block. Turns out this trick was used by the Crosley COBRA engine as well, which faced a similar problem. Goes to show, not all ideas are new ones.


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PostPosted: November 8, 2014, 9:39 pm 
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Is the Crosley COBRA engine the stamped steel engine type?

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886


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PostPosted: November 9, 2014, 1:18 am 
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Yes it is, Lonnie. COBRA = COpper BRAzed. A very interesting concept.

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"Orville Wright did not have a pilots license." - Gordon MacKenzie


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