Restoring Cox Engines in general

I read with interest the postings following the advice on restoring Jason's Strato bug. Rather than follow the same topic, I would like to start a new one that follows the same lines but is more general.

Firstly, my techniques are not for the faint hearted. I have no concept of health and safety and believe that everyone learns from their mistakes but caution is advised as these procedures can be dangerous if care and protection is not taken. You could also ruin what was to be your pride and joy and so I would recommend practise on less valuable engines.

This is what I started off with (earlier this afternoon) and selected a grotty crankcase from a bug and a tank from a bee. No fuel tubes to keep it simple.







Both beset with corrosion.

This is not always easy to remove with abrasives as some areas are more corroded than others and the corrosion runs deeper. Using abrasives can result in too much material being removed and so I embark on chemical warfare from the very start.



Firstly, tie the offending objects using a plastic coated wire. The reddish liquid you see is sodium hydroxide - started off clear but has been used on many metals and adopted a reddish hue- this liquid will strip skin, blind and during the process gives off nasty and very unhealthy fumes.



Within a few seconds bubbles appear and this accelerates.



We are talking seconds not minutes! Leave it too long and the parts will dissolve. All gum, varnish and oil will be removed in seconds together with the corrosion.

Then the parts are taken out and rinsed in water.




Then the second phase of chemical warfare - desmutting! This is nitric acid - again, very user unfriendly, corrosive and the process gives off even worse fumes.



Followed by another rinse.



This whole process took less than 40 seconds. Not enough time for a cigarette!

Then all that needs doing is a quick wipe with paper towel and the application of some fine steel wool. I use "0000" grade. This can be manual or:-



How long depends on the finish you like - a quick skirmish with just the fine steel wool gives a very clean finish - on the lathe we are again talking seconds. If you want a shiny finish then use polish with the steel wool.





The polish for the tank was completed in two minutes whuch included the chuck change. Please also be aware the fingers near spinning lumps of metal in a lathe is also not considered a good idea but I do it!

It is not necessary to use machinery and in the example of the crankcase I just gave it a quick rub over with the steel wool and polish. About a minute.



Note dirty fingers.

This although clean wasn,t shiny enough for me and so a few seconds with a polishing bob on a dremel.




Then wipe over with a cloth and :-







Some of the polish needs removing with cotton buds but the whole start to finish was less than 10 minutes, including a cigarette break. Not using machinery would only add a few more minutes and allow more control over the level of shine.

Please remember that following any of this has risk and I am not recommending it. Even steel wool can be embedded in fingers and eyes! Always be carefull and do not attempt anything without taking precautions to protect yourself.