ddd

Hi, My name is Bob Davis and I run a company in the hobby for over 32 years called Davis Diesel Development. for those of you that have never heard of us we manufacture diesel conversion systems for model engines here in the USA, so it fair to say were engine guys. After a long sabaticul from the car and truck business we came back to put our foot in the water and see what progress there as been since our work with the likes of the RC10GT and the Kyosho Infernos. We found out that the hot item was the Traxxas Revo so we bought one and for back-up we also bought the OS 18TM drop in. What we discovered is the reason for this little note to help modelers that use this truck. After we jamed the revo3.3 engine and had to use the recommended screw driver and flywheel prybar aproach we dicided there was a better way. so let pass along the fix.

You will need an electric drill first take the engine out of the truck and remove the easy starter and the glow plug. now slip a piece of fuel line over the shaft and lock it onto the shaft. Next put a little light oil down the hole and make shure to do two thing run the drill so the engine runs backwards. Start the motor and go to high speed once you feel no restriction you may release the motor and let it hang inverted whilr running tape or tie off the trigger and run through two battery packs which should give you a few hours.
what you have done is called cold burnishing and it will give you a harder surface on the piston and a more perfect seal for better compression and power.

PS our Revo on diesel covers 160 ft in 3 seconds with stock gears.

Bob Davis

Beasley1

So your running a nitro engine on diesel. You gotta post a vid for us.

JB COMP

so you broke in the engine with out starting it????

and on your diesel engines, do you run the same diesel fuel like you get at a citco, bp, etc...

ddd

The model diesel ignition system goes back to the late 30's, glow came into the hobby in the late 40's. In 1975 we decided to make what is a semi diesel namley your glow engine into a full blown diesel. It has no glow plugs and it uses the same carb as glow. for example the revo runs its main at about 3 1/2 turns and the diesel runs at less then 2 turns so its safe to say it uses about half the fuel. It is a kerosene base fuel with starter chemicals and added lube. Our website gives a pretty good explanation of the system and how it works. It is for real and has been for many years its just been a secret to the car and truck guys, woops!

89ram

diesels are powerful! i've seen the airplane motors, monster truck diesel motors would be sweet!

ddd

you can view the revo's with both the 3.3 and the OS 18TM by going to YOU TUBE and typing DIESEL REVO These engines are still breaking in.

joelgould111

wow ddd i like the sound of the break in procedure please can you explane in more detail as i will be running in my new picco.26max in this way lol like where do i put the fule line and were do i put the drill on the shaft some pics would be nice lol thank you joel

holeshotkid

Wouldn’t this method starve engine components of the proper lubrication that they need? I can only imagine what the rod bushings and crank bearings go through during this type of break in procedure. I am, however, intrigued with the diesel conversions…

hardcharger81

I too am interested, and would like to run my truggy on diesel. Is there any plans to make more conversions of more motors?

ddd

We said you put in some light oil the engine will hang from it own weight upside down while running so you can see it does not wear anything but rather removes small high spots on the piston.

ddd

Put a piece of fuel line over the shaft before you lock it in the chuck of the drill. Remove the glow plug and put in some light oil. hold the engine upright and beshure to run the drill in reverse the that their is no base compression to overcome just the friction of the piston to the cylinder. It shoul be don it 2 to 4 hrs reoil every 1/2 hour. you wil not hasve to hold the engine for very long you will be ableto let it turn upside down while running.

ddd

yes

joelgould111

what bit of the shaft the starter shaft or the crank shaft lol can you put soe pics up im still a bit baffled lol

ddd

I really don't know what it is that you do not understand. But I'll try, to protect the threads on the crankshaft you put a piece of fuel line before you tighen the chuck on the drill.

hotrodf1

So for this "break in", it removes some machining tolerances, and lets everything wear together a bit without the added load of compression, etc., right?

Would you still need to do the Traxxas recommended break-in method after doing this with the drill? I am very curious about this, as I've never heard of doing this before.

DaveG55

Courious is not the word that I'd use. Leary is more like it. I'm not sure why I want to eliminate the pinch. Pinch on a nitro engine is a good thing.
Assuming that both methods accomplish the same thing, breaking the engine in, then it seems to me like the heat cycle method is easier, faster and a whole lot more fun

ttoks

i agree with dave, although if breaking in the engine cold, that would mean that once the engine got to operating temps the top of the sleeve would be larger diameter then the bottom? so no compression? and maybe even piston slap, doesn't make a lot of sense to me.

ddd

After 32 years in the model engine business that anybody would think that we would tell you to do someting to hurt your engine come on fella, not I. I'll will try to make it clearer for those that don't quite get it. There are two ways to make a model engine with regards to its piston fit. Almost perfect and requiring little breakin OS engine and blue printed engines by EB or make it tight and leave it to the modeler to wear it in by running untill it become correct, or not. All model engine cylinders are tapered and are smaller at the top and bigger at the bottom were a good seal is less important. A pinch is when the fit is too tight and you do the work. When an engine is blue printed meaning improving the fit it is done by hand not by running. The cold lapping method has one added advantage it re-orients the grain structure of the surface of the softer item the piston and makes it denser and thus harder then before. So what your doing removes the need for a less controlled in truck breakin. you will still need a few tanks to make it perfect. And for those that never heard of such thinks before, now you have.

Bob Davis
Davis Diesel Development

DaveG55

Bob, you're going to have to excuse me for remaining skeptical. What you are saying seems to be to be counterintuitive and your examples of blueprinting and tight tollerance manufacturing don't, at least to me, seem relevent to breaking in an engine. Even OS and RB tell you to break-in an engine as does every other engine manufacturer that I'm aware of, be they high or low end engines. Even you statement that "a few tanks to make it perfect" seems to negate the need for your procedure. After all I have to do break-in now and "a few tanks" sounds suspiciously like break-in anyway. One other thought that keeps occuring to me is, If this is such a good idea why haven't the engine manufacturers started doing this as part of the manufacturing process? If it's such a good thing they could save 10's, if not 100's of thousands of dollars in warranty support costs. Not only that, they could advertise the engine as "pre broken-in" something that I guarentee would sell many thousands of vehicles and engines.
I would like to kmow more about the metalurgy behind the "cold lapping" advantages you describe. Do you have any links to relevant research, machinest or metlurgy sites that describe that?
Also, please don't take this as a put down or dismissal. I'm willing to learn new methods and procedures but I'm not the kind of guy that does well with "because I said so" as an explanation. I really need to see facts, research, etc to tell why/how something is an improvement.

hotrodf1

I guess I was under the impression that the fit up of the piston and sleeve changes as the temp changes, right? (due to different expansion rates of the different piston and sleeve materials)

If that's the case, then why would there be an advantage to having a "perfect" fit up when the motor is cold? Won't that mean that the fit is no longer proper when the motor heats up? Like a worn out motor that looses power and dies when it gets warmed up.

Not trying to be a doubting Thomas, but it just goes against what I "think" I know. And I'll admit there's a lot about nitro I don't know.

ddd

Hey Dave your one of those guys that just doesn't get it and for t hat i'm sorry but i can't make it clearer. you never owned a OS engine and if you had a very tight engine you must have thought it must be that way for a purpose. As for learning more about cold lapping do some research. This concludes further discusion on this subject from me.

hotrodf1

I don't think we are trying to put your method down, just trying to discuss the details and hows/ whys.

I am still very curious about how the cold-lapping helps run the parts in to proper fitup, when the motor never runs at that temperature. Can you please explain?

ddd

This is my last try.

The piston and the cylinder expand at the same rate so if you heat them or leave them cold it makes no difference. In an ABC system it is only when you overheat the engine does the cylinder out expand the piston and compression is lost and the engine stops safely. I trust this is very clear now.

DaveG55

Hey Bob, why would you talk down to me like that? You don't know me or anything about me. For the record I've been using nitro rc engines since 1965 and I learned from my father, a machinest with half-a-dozen patents to his name and a modeler since the early 50's. I've been around nitro engines all my life and own some that are considerably older than I am. I currently own 4 OS engines one of which is 20 years old and running strong on the factory break-in method, along with several other engine in all quality levels. Also, I do know a good amount about how rc engines are constructed and how they operate and what occurs as the operate and your condecending tone to me (and others on the board) is not a welcome one.
I had defended you on this board before but I now see that I was premature in that. You can also be assured that I for one will not be buying from you, nor reccomending that anyone else does. In fact, if you were to send me a free sample (yeah right!!) I would return it to you unopened.
And,
"This concludes further discusion on this subject from me."

TheKennyKiller

settle down mate ... your going to give your self a hemroid