1QwkSport2.5r

There is a driver hub/collar that goes onto the crankshaft, then the prop, then the prop nut. Car engine crankshafts have the same size for the most part so it fits most engines. No special design, it looks like a normal wide blade prop with the tips cut off similar to a Master Airscrew prop.

There is a link earlier in the thread to the prop, drive collar, and prop nut.

eemilioc

1QwkSport2.5r
The hudy prop has a very high pitch and has some irregular cuts that I imagine are for creating turbulence and increasing the resistance. The other setup that was mentioned before had a simple prop cut on both ends, so there is where I think the resistance is equal in any motor, while the hudy may vary its resistance due to this additional cuts. This is just what I have thought by guessing and looking at the pics.
I have searched for this prop and they dont sell it anywhere, if someone had it and gave us some dimensions and photos would be great to calculate the pitch and fabricate something close to the original.

purenitro33

I wasn't referring to the other links, only the link that was in my reply. You should never set an off-road engine to operating rpm for break-in, the heat generated from the friction and the load put on the moving parts would damage the engine in short order.

1QwkSport2.5r

That's why the engine needs to be lightly loaded and set rich. Get the thing running, get it hot, and let it run. The light load lets it turn up, the rich mixture keeps it lubricated and cool.

Not rocket science. You guys make it sound more complicated than it is. But don't worry... I won't hold it against ya'll... . I'll agree to disagree again.

purenitro33

Your theory may be relative and doable with rtr engines that have butter soft pistons and cheap chrome. But try that with a high end engine and you will find it simply doesn't work like that, the heat cause by friction will send the temps skyrocketing at operating rpm, and adding more fuel to the equation doesn't solve that.

You can disagree all you want, but your arguing with people who make a living building and selling these engines. If break-in was just that easy, my life would be so much more simple.

controlliner

I have broke in many ABC engines with hard chrome brass liners and high silicon content aluminum pistons. All run rich and never any problems. I have only run them hot enough to stay running. I have a traxxas 2.5R engine that has 15 plus gallons on it and it has the original OEM rod in it as well as original piston and liner. It only takes a few degrees above ambient temp to obtain safe running clearances between the piston and liner. This particular has a real squeaky pinch when it was new too and the rod never broke. Nor did the bushing wallow out on the crank pin end. Save heat cycling for the Meehanite piston engines, that is where the process began and got slurred over to the ABC engines. A high silicon content piston has a very low expansion rate and doesn't retain any growth once heated like meehanite does.

supertib

what exactly is the debate here ? I don't even understand what you guys are disagreeing about ? I Would consider myself quite experienced breaking in ground engines...I have successfully broken in several thousand race engines over the last few years..so not sure what the debate is....

rccheech

So very true, You will never over rev the engine on a break in bench, and spinning the engine to max rpm during break in will cause every bit of damage imaginable. Its about seating the bearings, and matching the sleeve to the piston, needs to be done by inreasing the rpm range gradually. The load that the prop puts on theese engines is more than the engine will ever see in its lifespan.

JohnP2

Ha! I was wondering the same thing. Hey, what do you guys think of the O.S. 21XR-B? I've never seen an engine marketed to be easily upgraded. Wouldn't it be more cost-effective just to order the one you want instead of investing in upgrade parts?

Anthoop

Plenty of low rent engines can be upgraded with parts from other engines already....I guess they are only saying it to try and increase sales....sales patter.

JohnP2

Understood. I'm curious, however, if it is cost effective. Example: would one spend more getting an O.S. 21XR-B and buying parts to "turn it into" a 21X-B V-Spec (or something compatible)....as oppossed with just buying the 21X-B V-Spec. Thanks

rccheech

In most cases by the time you get the piston, sleeve, rod, crank and (sometimes bearings) you will have just about spent the same as purchasing a new mill.