Bog's Paddleduck Engine

Gallery, Projects and General > Project Logs

<< < (24/45) > >>

bogstandard:
Kirk,

If the engine is built to plans, the measurements should be almost spot on.

No-one has come back with any problems such as yours, and it seems enough allowance was made on the parts to allow the engine to be tweaked into the correct position for running.

It might be that you are not following the plans in the correct order, and are using the wrong measurements, and also because you are scaling up, maybe the allowances are not correct for your engine. This is always a problem which changing scales

If you have a look at the two extracts, it shows there are two different lengths for the rod. The first to allow the rod/piston combo to be made, the second, where the final lengths have been found. Are you using the first measurement?, as that will certainly give a rod that is too long.

If you look at the difference between the two lengths, multiplied by your scaling up, it is showing something close to the error your are finding.

John

kvom:
Yes, I missed the second part. Thanks for pointing it out. I wasn't too worried since it was/is going to be straightforward to shorten the rods.

In the meantime I drilled/reamed the packing glands, and will be drilling/tapping the mounting screw holes next.

bogstandard:
Kirk,

I am sure you will get it all running just fine.

You still have time to bore it out bigger and turn it into the monster you are after.

John

kvom:
One step forward, two steps back. :scratch:

I drilled the gland mounting holes and the block, as can be seen. Why the missing screw? Because there's a broken 5-40 tap in the hole. :bang: So I will get a chance to try to dissolve it out a bit later. In the meantime it's not holding up progress.

After screwing down the glands my piston rod/piston assembly wouldn't go in; turns out the thread on the piston iend of the rod is slightly tilted, so scrap one piston rod. In addition, I had a bright idea that instead of cutting an external 8-32 thread on the crosshead end of the rod, I would drill and tap an 8-32 hole in the end and use a bit of 8-32 screw for the connection. In theory it should work, but the two I tried ended up with the hole slightly off center. At least the threads were straight. I still have enough 3/16 drill rod for 4 or 5 more tries at good piston rods.

It's getting "tricky" to figure the sequence for putting everything together. I believe the best approach to connect the bottom and top sections is to have the crossheads as part of the top, so that you need only bolt the crosshead to the conrod and the top plate to the columns (haven't made the eccentric linkages yet).

--- Quote ---You still have time to bore it out bigger and turn it into the monster you are after.
--- End quote ---

In reality I chose to go bigger so that I could work with bigger parts (I'm still not too confident working at small scales). Given that the displacement will be 3.4 times the original, it may be a "monster" already. The air channels will be only 2.25 times larger in cross section, so it will be interesting to see how much air it will need.

CrewCab:

--- Quote from: kvom on June 13, 2009, 04:34:07 PM --- there's a broken 5-40 tap in the hole.

--- End quote ---

Dammit, that's a bug**r ..... hope you manage to get it out Kirk ............ the build is coming along very well, really enjoy following it, thanks for the progress reports.

CC

Navigation

 Message Index

Go to full version