Starting with the Boll Aero 18

[Richard Hed]

Thanks for the tips. I'll have a look into turning the crank as one part.

How do you approach turning a crank? At the moment I think I would do it between two centres

Joe P has some good vids on utub :

There are also the 4-jaw chuck methods. Just one cylinder? Not so difficult.

 

[Richard Hed]

hello here is another similar to bolero motor its called nelson 2cc .free download

Where do I find that?

 

[ixb1]

Uncle Google say Here:
http://www.machineconcepts.co.uk/engines/nelson/nelson.htm

 

[Sprocket]

Yea if it rotated in the collet the the setup would be ruined. The collet had a good hold and I took very light passes.

It wasn't possible for me to put it directly in the 4 jaw Chuck as the small diameter of the shaft combined with the offset ment on of the jaws wanted to pass the centre of the chuck. As a result the two perpendicular jaws couldn't be used. Collet directly in the spindle wouldn't allow for throw turning and so I opted for the collet block in the 4 jaw option

Glad you explained the collet in the chuck. I was wondering about that setup.
Doug

 

[jimbo7636]

Its more ways to turn crankshaft. I personally turn them in four jaw chuck out of ht bolt.
Plans do not contain one important note- cylinder bore must be tapered!

im planning to build this engine and I dont know how to quantify the taper. I presume its tighter towards the prop. any help here would be appreciated.

 

[ixb1]

Cylinder taper is simply larger diameter at bottom end about 0,01-0,02 mm. Piston at bdc have clearance(meaning less drag) and at tdc is tight.

 

[minh-thanh]

Just adding a few of my comments
I pretty much agree with @KenC 's comments
If I need the engine to run I won't care about cylinder taper. If the cylinder is straight or tapered, my engine still run - the important thing is the surface finish of the cylinder - I usually polish it
I have never lapped the piston vs cylinder with any abrasive.
Have I ever lapped a piston with a cylinder?? Yes, I have, but unless the piston can move a little hard in the cylinder with lubricant. And I will lapping them together with lubricant

 

[Nibby2226]

I lapped my cylinder very slightly tapered and then finished by "lapping" the piston with cylinder using oil only until it just reached TDC without binding.

 

[Olli-Matti]

im planning to build this engine and I dont know how to quantify the taper. I presume its tighter towards the prop. any help here would be appreciated.

Here is the article by KenC on the process of fitting and finishing the piston and cylinder. Highly recommended! I did follow these instructions carefully and have done since with good success.

THE PROCESS THAT ALL BEGINNERS FEAR: FINISHING AND FITTING THE PISTON AND CYLINDER by Ken Croft

-Olli

 

[jimbo7636]

Here is the article by KenC on the process of fitting and finishing the piston and cylinder. Highly recommended! I did follow these instructions carefully and have done since with good success.

THE PROCESS THAT ALL BEGINNERS FEAR: FINISHING AND FITTING THE PISTON AND CYLINDER by Ken Croft

-Olli

Olli, I finally got to this point with the ML Midge cylinder liner. I made the lap from brass and when I saw cut the slit I found the lap had opened up quite a bit. So maybe I didnt do a very good job sawing, but I tried to be careful. I might remake the lap out of aluminum, which I think is stronger than brass. Any suggestions? I tried squeezing the lap back into shape but I am concerned its too warped. I might just go with a parallel lap and try to have the bottom of the cylinder liner spend more time on the lap than the top. Update: made another one lap from aluminum and that worked better. Maybe the brass I had was not good quality.

 

[oxford]

Since this thread popped back up. Here is a pic of a Boll Aero that I recently completed.

 

[jimbo7636]

Since this thread popped back up. Here is a pic of a Bill Aero that I recently completed.

Nice job on the boll aero! Can you tell me what type of lap you used on the cylinder liner? I tried making one that is split by sawing and has a jack screw but the lap opened up too much for my liking after I sawed it.

 

[oxford]

Nice job on the boll aero! Can you tell me what type of lap you used on the cylinder liner? I tried making one that is split by sawing and has a jack screw but the lap opened up too much for my liking after I sawed it.

I didn’t make a lap for the cylinder or piston. My lathe is pretty clapped out so it cuts on a taper(which somewhat worked to my advantage on this). I did hit the surface of the cylinder with a fine grit ball home and then ran a 1/2” buffing wheel on the Dremel with some polishing compound.

The piston is straight, I then fitted until it was just short of TDC giving it a firm push by hand. Contra piston was fitted with a taper and a light press fit to collapse the side when it was put in.

 

[timo_gross]

Since this thread popped back up. Here is a pic of a Boll Aero that I recently completed.

On a scale from 1-10 how difficult is that engine to build? 10 beeing difficult!

 

[oxford]

On a scale from 1-10 how difficult is that engine to build? 10 beeing difficult!

I wouldn’t really call it “difficult”, it’s really just basic machining. Most important thing is watching tolerances of mating parts and keeping those fits good.

Drawings are good although I did make a few changes to suit. Mostly to the prop mounting.

 

[timo_gross]

I wouldn’t really call it “difficult”, it’s really just basic machining. Most important thing is watching tolerances of mating parts and keeping those fits good.

Drawings are good although I did make a few changes to suit. Mostly to the prop mounting.

Thank you for reply, another difficult thing seems to be to get the fuel from somewhere. It seems like a project in itself, so I reconsider things.

 

[oxford]

Thank you for reply, another difficult thing seems to be to get the fuel from somewhere. It seems like a project in itself, so I reconsider things.

I mixed my own. John Deere starting fluid, kerosene, castor base 2 stroke oil. Equal parts

 

[timo_gross]

I mixed my own. John Deere starting fluid, kerosene, castor base 2 stroke oil. Equal parts

Can a diy mix be tested (without injury?),without motor? I fear that it is not "beginner friendly" to try debugging fuel recipies and faulty manufactured engine at same time.

Greetings Timo

 

[Ghosty]

Can a diy mix be tested (without injury?),without motor? I fear that it is not "beginner friendly" to try debugging fuel recipies and faulty manufactured engine at same time.

You can read this, all about fuel. The fuel is safe if you don't mess around. I have been mixing my own fuel for almost 40 years and never had a problem.
A 1/3 mix of Ether, Kero and oil is a very stable fuel mix that will work in all model diesel engines.
https://www.adriansmodelaeroengines.com/catalog/main.php?cat_id=72
Cheers
Andrew

 

[timo_gross]

You can read this, all about fuel. The fuel is safe if you don't mess around. I have been mixing my own fuel for almost 40 years and never had a problem.
A 1/3 mix of Ether, Kero and oil is a very stable fuel mix that will work in all model diesel engines.
https://www.adriansmodelaeroengines.com/catalog/main.php?cat_id=72
Cheers
Andrew

No! Misunderstanding, I am not scared of the fuel, I am scared that the engine is not running and I cannot tell if the wrong fuel mix is the reason or some problem with the engine. (because it will be the first engine ever)
If you can buy a proven mix of fuel, like in the UK; focus can be on the engine in case it does not run.
I will check out the link anyway thank you.
Maybe it would be more advisable to start with a propane fired engine or some gasoline thing?