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Dieselized, TD .010

Old 10-26-2009, 11:24 PM
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AndyW
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Default Dieselized, TD .010

When it became clear that Cox was not going to make any, any more, the problem of a shortage of glow plugs came up. With the .049 size, it was fairly straight forward to adapt a burned out head to take turbo plugs. I also tried this on the .020 size but couldn't get a good result. A logical solution would be to dieselize and eliminate the glow plug entirely.

I don't have any pics to show for the moment but I gave that a try on the TD .010.

There was no problem making a head but when it came to starting the little jewel is where I ran into trouble. I stuck with my 39/39/20/2 formula to start. I used the spring starter all the way and had a very hard time getting the engine to run. I went to an all ether prime with 40% oil but this didn't help much. In the process, I damaged two of those precious, little cranks. On one, the crank web bent at the pin. On the other, the pin broke off along with a bit of web material.

Getting the precise compression to light off the prime was the problem. It was too easy to be undercompressed with no start and just as easy to be overcompressed. So much so that once she lit off, only 1 second or so, and the crank broke. At first I blamed the crank for not being strong enough. Now I'm thinking that the use of a 2/56 compression screw was the problem. The threads are just not fine enough to get a precise setting. Especially with a spring loaded compression screw.

I'm now down to ONE complete engine and two broken cranks. And lots of .010 bits and pieces. I won't be trying this again until I find more cranks. Anyone have any trashed .010s they want to get rid of?

Or, I'll bet there's a tiny diesel out there with a stronger crank that might fit with a little fiddling. Any ideas, guys?
Old 10-27-2009, 01:00 AM
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Default RE: Dieselized, TD .010

Do you acces to a lathe? It will be easier to make own crankshaft of high tensile steel.. Do not harden the crankshaft, it will make the crankshaft brittle..
Old 10-27-2009, 02:26 AM
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AndyW
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Default RE: Dieselized, TD .010

Well, I do have a lathe and I guess I could try. I've heard that there is a bolt grade that works well for cranks.
Old 10-27-2009, 06:39 AM
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Default RE: Dieselized, TD .010

Andy,

Maybe when you try again, you could preheat the little one with a heat gun to try and ease the starting burden.

I have no personal experience of doing this, but it seems logical to me.

Regards

Greg
Old 10-27-2009, 07:09 AM
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AndyW
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Default RE: Dieselized, TD .010

Hi Greg,

I believe I was the first to stumble on that idea a few years ago here, http://www.youtube.com/watch?v=_VA1R...er_profilepage and I did try that trick and it did, in fact, make a start possible when nothing else worked. Especially in light of the ambient temperature at the time,, raining and only 5C above. It was under these conditions that I originally used the heat gun and found, just as with several prime runs, heat would make the engine much easier to start especially with a no ether fuel.

In retrospect, maybe I should have tried something like a 50% ether formula. This is SUCH a tiny engine. The other issue, I'm convinced, is that like most Cox engines for the last ten, maybe twenty years, they've been set up with such a just so fit, no need for any break in of any sort, that the compression seal isn't what it should be. Both my PAW and MP Jets diesels needed a measure of break in and both exhibit that nicely polished piston you get with a nicely broken in engine. Many of my Cox engines, on the other hand, show a brown stain on the piston indicating significant blow by and loss of compression seal. This could be why the .010 required a very wet prime to even light off.
Old 10-27-2009, 09:53 AM
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Default RE: Dieselized, TD .010

Andy, How did you seal the contrapiston?
Old 10-27-2009, 10:25 AM
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Default RE: Dieselized, TD .010

With a Viton O-Ring. The fit was such that even though I used a spring to load the compression screw, it wasn't needed to hold a setting. It certainly wasn't leaking, I made sure of that.
Old 10-27-2009, 10:45 AM
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Default RE: Dieselized, TD .010

About Cox compression seal again. I have a piston/cylinder set that I made by honing out an .049 cylinder to fit an .051 piston. This one has lots of taper in the cylinder and a bit on the piston. This one behaves much like a new Norvel. It snags at or near TDC if you don't flip it over smartly. But it does flip over easily and starts by hand and runs as strongly as any other set I have. That polished look on the piston is there and with that tight fit, I'm speculating that this set will last a long time. Unfortunately, I can't do this with the .010,,,, or can I? I have an idea that may work. Need to test it on one of my less precious .049s first. If it works I'll post the results.
Old 10-27-2009, 10:49 AM
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Default RE: Dieselized, TD .010

Meanhwile I found a thread from Rocketrob about Schlosser diesels, one of them a .25cc. That's small and looks like a crank that could be made to fit. But the engine itself is some 250 dollars, virtually hand made. So I'm sure that a crank from one of these gems would be nearly a hundred bucks. []
Old 10-27-2009, 10:59 AM
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Default RE: Dieselized, TD .010

Did the piston cylinder set hold pressure for any length of time when brought up to TDC? In past discussion about tiny diesel people have said that if it doesn't have that bouncy compression and doesn't hold for at least a few seconds you can forget about it running. I have an AE 0.1cc. I have yet to try running it. 40% ether should be good for the fuel and has also been mentioned when talking tiny diesels. The AE papers recommend 30% ether for the larger sizes and the addendum for the 0.1 does not say anything about fuel, only prop.
Old 10-27-2009, 11:29 AM
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Default RE: Dieselized, TD .010

The Brits are known to pull out a torch to heat the heads on their diesels on cold days. I've had 40-50% ether recommended to me for small diesel fuel mixes (for my Pfeffer as I recall), they suffer the same thermal efficiency issues as small glow engines and ignition gets spotty as a result without excessive compression. As I recall 40% was recommended for my Pfeffer. The .010 as it is on glow needs a bit of coaxing to get the cylinder up to temp and run smoothly at times. On diesel I wonder if you might end up with excessive cooling once running?

Darned .010's just aren't built for high cylinder pressure. Hope you can conjure up a workable crank/crankpin.

MJD
Old 10-27-2009, 12:15 PM
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Default RE: Dieselized, TD .010

ORIGINAL: AndyW

Well, I do have a lathe and I guess I could try. I've heard that there is a bolt grade that works well for cranks.
Be sure all surface are well polished to prevent galling..

The .010 as it is on glow needs a bit of coaxing to get the cylinder up to temp and run smoothly at times. On diesel I wonder if you might end up with excessive cooling once running?
Although the volume is so small, so the engine could go.

See at the Nano model engine has 0,1 cc/0.0061 cubic inch cylinder volume, the bore are 5 mm, stroke 5 mm. The engine are reving up to 40 000 rpm [X(]

Did the piston cylinder set hold pressure for any length of time when brought up to TDC?
The piston/cylinder fit are critical for smaller engines.. I will prefer a tapered cylinder instead a parallel cylinder. Mostly Cox engines are parallel since the cylinder/piston are made of steel. When the engine are well used as a glowplug engine, the fit can be more loose and will not keep compression in longer time hence the engine are unuseful as a diesel engine.

Edit: wrong text..
Old 10-27-2009, 02:54 PM
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Default RE: Dieselized, TD .010

That appears to be the problem, then. No bounce or compression hold at TDC for any length of time. And this is on a nearly new piston and cylinder set. But there may be a way to cinch up the fit and at the same time, impart some taper. Will try and work on that this week. Temps 10C above zero for a few days at least. [8D]

Greg,

You have an .006 diesel engine? So I did a search. http://modelenginenews.org/cardfile/ae.html

Looks ideal for some of the small electrics out there.
Old 10-27-2009, 03:05 PM
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Default RE: Dieselized, TD .010

Relative to the crank, that pin looks pretty robust. No danger of anything breaking there. Looks like that's part of the problem too,,, the Cox crank is too lightly built for diesel. Maybe I WILL have a go at making a crank and make it similar to the AE crank. Thanks Greg.

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Old 10-27-2009, 03:37 PM
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Default RE: Dieselized, TD .010

I've been itching to run the AE 0.1 lately. If I do it I'll post here with a youtube clip. There are more than a handful of engines out there with no counterbalance. The MVVS 1.5 is one I've owned.

You could start with a grade 8 bolt or and socket cap screw. Both should be strong enough. I've not tried making a crank from bolts or any other material yet. It's on my list. As soon as I get my Clausing going to replace my old Atlas more projects will be within the realm of possibility. The old Atlas is getting tired and sloppy. New bushings for the countershaft would take care of the vibration, but it would still cut a taper near the headstock.

I've heard of people heating Cox pistons to cherry red and quenching in oil, then lapping to fit the cylinder. I don't know if this is valid. And it seems it would do a number on the surface finish of the piston. I had a TD .049 that I assembled from loose parts that had a piston to cylinder fit as you described, like ABC. I only ran it a bit and sold it. It ran well.

Jens, I saw your helical gear cutting clip on youtube. Very impressive.How did you make the cam for attachment? It looks like flat plate rolled to fit. Which engine are you building? Feeney perhaps?
Old 10-30-2009, 03:01 PM
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Default RE: Dieselized, TD .010


ORIGINAL: gkamysz

Jens, I saw your helical gear cutting clip on youtube. Very impressive.How did you make the cam for attachment? It looks like flat plate rolled to fit. Which engine are you building? Feeney perhaps?
Hi Greg, here are the pic of the helical gear and how the angle are measured before i maked the rolled angle plate on indexing head.

The steel drum with rolled angle plate are rolling around the center shaft in the indexing head, locked with locking screw and gearwheel as indexing disk. The ball bearing are fixed to milling machine.

The gear cutting wheel are selected by the formula: Selected number of tooth on helical gear/Cos3=number of tooth on gear cutter.
Also there are not same tooth profile in a helical gear as in a spur gear for same number of tooth.


http://www.youtube.com/watch?v=HcG9Eoyf9aI
http://www.youtube.com/watch?v=XBhzBmErbjY

The helical gear are to a stationary gas engine.

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