BollAero Major 4.4 (oz14657)

 

BollAero Major 4.4 (oz14657) by Chris Boll 2011 - plan thumbnail

About this Plan

BollAero Major 4.4 cc. Diesel engine.

Direct submission to Outerzone.

Quote: "I am the designer of this engine, which has been built by many others, and wondered if you would like to have the plans on Outerzone. It is on 2 sheets and appeared in AMI magazine in 2011. I have pdf scans. Regards, Chris Boll"

Plan cleanup by Circlip. Article scan here is thanks to RFJ.

Article Quote: "Boll-Aero Major 4.4. Two years ago, our construction feature on Chris Boll's original 1.8 cc diesel drew much interest. Now he offers a larger 4.4cc option.

This is my second design for a home made engine, my first, a 1.8 cc diesel appeared in AMI in 2008, and I was very pleased with the positive response which I received from people, including several from outside the UK.

There are very few model aero engine designs available which are really simple to make. In the past, they were designed by expert model engineers such as Edgar Westbury and Laurence Sparey, who used complex shapes which were either made from castings or required a lot of delicate machining. Their designs are still built today, and various casting sets can be obtained, but times have changed since these notable pioneers were active and today there are probably fewer people with the traditional machining skills, nor local foundries willing to make castings in low volumes.

It may be a factor in early designs that many model makers were still using treadle powered lathes, so were anxious not to have to machine away much material due to the effort involved.

So I decided to try another design that is machined from bar stock, but this time with front rotary induction, which I realised is not at all difficult to make, and means that the timing can be optimised more, although it is still very conservative.

This engine is designed above all to be simple to make for the home builder, many of whom, like myself will be primarily aeromodellers, rather than experienced model engineers. It is based on readily available aluminium alloy bar size and no castings are needed. If this is to be your first home made engine, please be assured that it is just as easy to make as my previous 1.8cc, and due to the larger size, is probably even more tolerant of less than ideal fits for the piston and crankshaft.

It runs well, is very easy to start, and has enough power to fly vintage style free flight or R/C models of around 60 inches span. It has a long stroke, which is similar to the early diesels made in the 1940s. This makes it easy to achieve sufficient compression to fire easily when cold, even if the piston fit is less than ideal.

The maximum speed is relatively low, but there is a good torque output, which allows props of 12 inches diameter to be used. With a piston bore of 0.625 inches and stroke of 0.875, the dimensions are identical to a Kemp diesel which was one of the first to be made in England, although I only learned of this similarity from the excellent www.modelenginenews.orq website after I had made my engine.

I arrived at these dimensions because the 0.875 stroke was the biggest crankshaft throw that could be accommodated in the 1.5 inch wide block of alloy that I wanted to use. The ratio of stroke-to-bore of 1.4 : 1 is also the same as the Mills diesels that have remained popular for over 60 years and are still being manufactured in India and China. The Mills range were never the most powerful in their class, but have very easy starting and running characteristics which make them a pleasure to use. I sometimes think that modellers put too much emphasis on sheer power output when choosing an engine because, for the average sports flyer, robustness and ease of operation are more important.

This 4.4cc engine is both physically large and heavy compared to a modern engine of similar displacement, but then it is not intended to be used in a scale Spitfire or a prop hanging Fun Flier, so I make no apologies for this. In the intended application of Vintage R/C or Free Flight, a bit of extra weight is not a problem, my models always end up with lead in the nose anyway. Adding mass to the engine ensures that it is physically very rugged and also helps to damp out vibration, so it is surprisingly smooth running, bearing in mind there is a large cast iron piston, which changes direction 200 times a second at 6,000 rpm..."

Supplementary file notes

Article.

Corrections?

Did we get something wrong with these details about this plan (especially the datafile)? That happens sometimes. You can help us fix it.
Add a correction

BollAero Major 4.4 (oz14657) by Chris Boll 2011 - model pic

Datafile:
  • (oz14657)
    BollAero Major 4.4
    by Chris Boll
    from Aviation Modeller International
    January 2011 
    4.4 cc
    Engine Diesel
    clean :)
    complete :)
    got article :)
  • Submitted: 14/06/2023
    Filesize: 535KB
    Format: • PDFbitmap
    Credit*: ChrisBoll, Circlip, RFJ
    Downloads: 588

BollAero Major 4.4 (oz14657) by Chris Boll 2011 - pic 003.jpg
003.jpg
BollAero Major 4.4 (oz14657) by Chris Boll 2011 - pic 004.jpg
004.jpg
BollAero Major 4.4 (oz14657) by Chris Boll 2011 - pic 005.jpg
005.jpg
BollAero Major 4.4 (oz14657) by Chris Boll 2011 - pic 006.jpg
006.jpg

Do you have a photo you'd like to submit for this page? Then email admin@outerzone.co.uk

User comments

Thanks Chris for sending this in.
Circlip - 03/07/2023
I have the greatest admiration for the "watchmakers" who craft these precious little machines, and then go out and make them actually tick!
Miguel - 03/07/2023
Unfortunately, when the publishers re annotated the dimensions on the original drawings they didn't go the whole hog and redraw the components. Crankcase needs careful observation.
Circlip - 03/07/2023
Dear Admin, please find attached a photo of my BollAero 4.4 while it is running today [pic 006]. I made this engine 10 years ago thanks to the great Chris design. This engine still runs great!! It was completely made with a mini-lathe and a mini-mill, it was just adapted, for obvious reasons (I live in Rome (Italy), to the metric system. Thanks again Chris!! Antonio Tafuto, (Rome)
Antonio Tafuto - 27/08/2023
Add a comment

 

 
 

Download File(s):
  • BollAero Major 4.4 (oz14657)
  • Plan File Filesize: 535KB Filename: BollAero_Major_44_oz14657.pdf
  • Supplement Filesize: 11020KB Filename: BollAero_Major_44_oz14657_article.pdf
  • help with downloads
 

Notes

* Credit field

The Credit field in the Outerzone database is designed to recognise and credit the hard work done in scanning and digitally cleaning these vintage and old timer model aircraft plans to get them into a usable format. Currently, it is also used to credit people simply for uploading the plan to a forum on the internet. Which is not quite the same thing. This will change soon. Probably.

Scaling

This model plan (like all plans on Outerzone) is supposedly scaled correctly and supposedly will print out nicely at the right size. But that doesn't always happen. If you are about to start building a model plane using this free plan, you are strongly advised to check the scaling very, very carefully before cutting any balsa wood.

 

Terms of Use

© Outerzone, 2011-2024.

All content is free to download for personal use.

For non-personal use and/or publication: plans, photos, excerpts, links etc may be used, provided that full and clear credit is given to Outerzone with appropriate and specific direction to the original content i.e. a direct hyperlink back to the Outerzone source page.

Unauthorized use and/or duplication of this material without express and written permission from this site's owner is strictly prohibited. If we discover that content is being stolen, we will consider filing a formal DMCA notice.