Old Timer

Old Timer Electric Conversions – Part 1  1/2A Lanzo Bomber

I have obtained three Old Timer models for conversion to electric power.

This article describes the first model to take to the air and how I went about modifying it for electric power. For those who may not be familiar with the term “Old Timer” it basically refers to free flight style models many of which were designed prior to World War 2.  Typical construction is built up balsa framed fuselage and open structure wing & tailplane.  Early covering materials were usually tissue or silk and dope however many models are now covered in new generation light weight materials such as Litespan etc.

In case you are wondering how and why I got hold of three complete Old Timer models the story goes like this:  I got hooked on the idea of owning an electric Old Timer after watching the likes of Ray Halstead, Martin Lui, Colin Kahn and Michael Lui flying their Old Timers.  They always seemed to be having a ball with their models cruising around on balmy summer evenings.  This often extended after dark with the help of on board lighting.  Martin must have got sick of hearing me say “I must build one of these” because one afternoon an Email arrived giving details of a Trading Post add for a 1/2A Lanzo Bomber, a 70% Lanzo Bomber and a Senior Playboy at $50 each.  Now this sounded too good to be true and I had visions of dilapidated old airframes with most of the covering in tatters etc.  It’s a good thing that we decided to make the not insignificant trip to Powelltown as we were greeted with three well built models in excellent condition.  Enough of this trivia, lets get on with the first model which is a 1/2A Lanzo Bomber.

The little Lanzo has a 1200mm span polyhedral wing mounted on a raised fuselage pylon.   As can be seen in the attached pictures construction is built up balsa fuz and open construction wings and tailplane. 

The model was originally set up for R/C and powered by a Cox 049 engine.  I do not know the original flying weight however the model now weighs 560gms ready to fly. The original covering was heavy weight doped tissue however it had been painted with a clear polyester finish for fuel proofing which added more weight than I had expected.  I am surprised that it flew well with this set up as the CG would have been well over 50% of chord with the little Cox 049 up front.  I decided to convert this model first as I had recently bought an MPJet 3:1 Speed 400 gear box for the Old Timer that I was always wanting to build! The Lanzo is about 10% smaller that the other S400 powered Old Timers in our club.  However I figured that I could run less cells to save weight and still have enough thrust from the 10 x 5 APC E-prop that I was planning to use.  As it turned out the combination of 6 volt S400 motor and 6 x 600AE Sanyo nicads provides sufficient power to fly the model on relatively calm days.

The first task was to mount some servos and this looked like being a pain given the small access panel on the side of the forward fuselage.  The pull-pull control wires had also been cut to remove the original servos so I decided to remove the fuselage covering so that I had better access.  This turned out to be a frustrating and  time consuming job as tissue and dope stick really well to the fuselage stringers! It’s amazing just how much strength this type of covering adds as the fuselage became very flexible when all the covering was removed.  I had some GWS pico servos on hand and they fitted easily into the existing mountings.  A trip to K-Mart for some plastic covered steel fishing trace and the elevator and rudder were back under control.

An interesting feature of this model (and its bigger brother 70% Lanzo) is that only half of the tailplane has a functional elevator – the other side is the original free flight style construction with no moving surface.  At this stage I thought that elevator inputs would result in some strange rolling motions however this did not prove to be the case.

On to the front end and how to mount a Speed 400 plus gear box where a Cox 049 once resided.  The front firewall (bulkhead) was 8mm ply and had probably supported the Cox motor with an integral backplate mounting.  In order to get the CG somewhere near 40% I needed to hang the gear box out well in front of the firewall however its flange mounting lugs looked to be too wide for the narrow fuselage.  I pondered possible extensive modifications to the front end however a little voice kept reminding me of the KISS principal (keep it simple stupid!).

As can be seen in the photos three mounting struts were made from carbon fibre arrow shaft material and long self tapping screws pass through from the gear box lugs to the firewall.  As luck would have it the original mounting holes for the undercarriage attach points almost matched the gear box pattern so I made use of them for both functions.  A 35mm hole was made in the firewall so that the rear half of the motor could extend into the fuz. This allowed for a simple and neat connection for the speed controller.  The 20 Amp ESC/BEC simply hangs in the space behind the motor and the 6 x 600AE cell battery pack is located below it on the fuselage floor immediately behind the firewall.

I was intending to use one of the GWS indoor receivers however Martin convinced me that it would not have enough range given that these models can thermal quite well.  The only other receiver that I have on hand was a Hitek 555 which would not fit in the cramped space available so I made a second access hatch behind the servos.  The only thing left to do was to re-cover the fuselage which I did using Ozcover clear as it is very light and provides an Old Timer look.

So how does it fly?  Well I was so keen to give it a go that I dropped into the club on my way to work the morning after it was finished.  As I did not have any appropriate wheels on hand a couple of Futaba large servo disks were pressed into service.  This meant a hand launch would be required until some tyres could be added using foam piping.  Off she went with the little Speed 400 running sweetly.  The climb was satisfactory however full down trim was still not enough for hands off flight!  Once the power was reduced the nose up pitch reduced so I noted that some down thrust was needed however it was still very tail heavy in the glide.  The first flight lasted about 5 minutes and there was still plenty of power left.  I have subsequently extended the motor mounts a few mm and put in some down thrust however it is still a bit tail heavy.  Not to worry it can now rise off the ground on its revised wheels and will loop and roll and do those wonderful low/slow passes that I used to admire others doing.  Flight time is well over 10 minutes on low throttle and the slightest bit of lift takes her skyward.

All in all a very satisfying project for a very reasonable outlay – now about that big senior Playboy and the Speed 700 with 2:1 belt drive, 10 cells and 14 x 7 prop!!!  But that’s another story so stay tuned, see you at the field, and good flying.

Neil Spencer

*** 10 January, 2010 10:26 PM +1000 ***

Last updated 10 January, 2010

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