Geoff Potter's blog - RC Groups
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Posted by Geoff Potter | Sep 28, 2017 @ 08:02 PM | 2,100 Views
I find with my old timers that I just can't get the props I want to give the revs I want and so I make my own . I start with a wood , fibre glass or carbon prop that is available and then make it to the shape and get the revs I want , but of course if one chips or breaks it you have to do it all again . So I make a mould of it and then can make as many as I like and is repeatable and I can still mod it after its made .
I start by making a pin and nut , this pin for the hole and the nut in the bottom mould then mount the pattern on a hard wood top with the pin to hold it and then fill under it with model clay and shape to get the draft needed in the bottom mould . I make a bottom mould housing out of aluminium bar with holes to fill thru then lock the top to the bottom , some use bolts ,I use "G" cramps and nails for dowels , quick and easy and I'm not looking bits when putting together with a wet prop in it . I build dams around the holes so I can over fill it as the epoxy shrinks if one doesn't get all the air out of it when still liquid , then fill with epoxy mixed with aluminium powder , I try for about 15/20 % powder . I'm going to try steel powder one day as well if I find a supplier of small amounts . I forgot to put in there to release the master and top mould before clamping together . Leave for 24 hrs and then should be ready to pull the top timber off and leave the clay and master prop in the bottom mould .
Clean out the clay properly just leaving...Continue Reading
Posted by Geoff Potter | Sep 28, 2017 @ 08:51 AM | 1,881 Views
My friend motorcycle Pete received a generator from a 1920 truck to rebuild but it needed a new rear housing . It was made out of what they used to call pot metal in those days . Terrible stuff and the day after they made the item out of it , it started decomposing , so Pete asked if I could make a new one to replace it . Inside , it held two fixed brushes and one movable one and the rear ball bearing was out side the rear housing . I bought a block of 2011 aluminium 6" diameter by 5" long and then set about trying to measure the old one up and do a usable drawing and because of the shape it had assumed over the years I had to do a lot of guesstimating . The brushes had to go back the same as they were originally otherwise they wouldnt pickup the right windings on the commutator and so not work . The poles for the brush holders to swing on had to be insulated from the housing as well . Got started cutting metal and 17 hrs later I just have to do the cutouts around the extremity of the housing . This is where I'm at so far . I don't know how to put captions with the photos so if anyone wants to know anything , just ask .
Well I got the rest of it done today and it's finished,has come out quite good and the brushes seem to be in the right place so will deliver to Pete on Monday and he can work his magic on it and the guy will have a really good generator on his vintage truck....Continue Reading
Posted by Geoff Potter | Dec 23, 2016 @ 05:24 PM | 3,609 Views
Head gaskets are a time consuming item to make ,it doesn't matter how you do them . I've tried cutting , sissors, knife ,punch,special tools and so on . Just a pain in the neck !!! Now I just bite the bullit and make a jig system to suit and make what ever amount will fit in it and put the leftovers in a bag with all the other leftovers . Then go thru the bag to check before making a new jig or boring out an older one to suit the size you want . I make the inner hole jig first ,for no reason other than that's the way I do it and then the lock cap to suit it so it holds the material tight ,I punch and put all types and thickness of material in the jig to bore out so gives me a few choices of size and type to use on the engine . From 1 to 10 thou,alum ,brass, copper,oilite, card stock, just fill it and bore . When they are made I make another jig to suit the internal hole and put them all on and lock up tight and then machine the outer to the diameter required for the particular head . Job done ,still time consuming and machines required but when the engine has a groove for the head gasket ,I find that this is easiest for me . It's either fiddle for hrs and get frustrated or ,spend a couple of hrs and do it...Continue Reading
Posted by Geoff Potter | Dec 06, 2016 @ 10:51 PM | 3,447 Views
An oil pump drive shaft came in to have the seal area on it repaired as it was deeply scored ( in fact 6 thou deep ) so had to grind down to clear the marks and then he wanted it brought back to size , 12.5 ml , with chrome . So set up in my tank after the grind and just on 9 hrs later , 13.5 thou diam of chrome , and re grind to 12.5 ml Diameter shaft . Don't know if it will stay there or not but looks ok and didn't do any damage whilst grinding it so will keep my fingers crossed .
At the same time my friend who rebuilds magnetos asked me to make two Pistons for a twin cylinder V i think 900cc Swedish MCycle engine . I was given two cylinders I cast iron piston and two sets of rings and asked to make two aluminium Pistons for them at the same weight as the cast iron ones. Bit hard to decide how much alum to take out while still in the lathe ,which would be easier ,but to much out and I can't put it back . I will add some more photos as I go . Finally got the Pistons finished and was careful that they ended up the same weight as the original cast iron ones ,I think more by luck than good measure ....Continue Reading
Posted by Geoff Potter | Oct 05, 2016 @ 06:54 PM | 3,966 Views
I had the. occasion to need a muffler on one of my McCoy 60s in an OT event . I had tried some offerings by OS and Enya and a few others I had found lying around , but was never happy with the results . Dub Jett sent me a new one of his he said would do the job but I would have to make a mount ,with no leaks . I was worried about using the transfer passage to clamp against . So I made my clamp pull against the casting at the rear of the exhaust . Works well and doesn't come loose at all ,have even stopped checking it ! And looks reasonable .
Posted by Geoff Potter | Oct 04, 2016 @ 06:47 PM | 3,680 Views
Had to cut the old teeth of a clutch sprocket and then fit a new set . Geezuss they get work hardened couldn't turn them off so cut most of with angle grinder and then set up on a mandrel in the lathe with a tool post grinder and ground down to size and then turned out the new sprocket to suit . He wanted me to do a 4 start 2 turn scroll for the clutch operator as well but my lathe won't do 2 turns in 1-1/4 " so gave it a miss ....Continue Reading
Posted by Geoff Potter | Oct 04, 2016 @ 05:03 PM | 3,730 Views
My friend asked me to build him a Racer for electric OT . He supplied a Brown cut short kit ,two servos . I motor, and speedie . The rest was up to me , I had built one before and it weighed 9+lbs so I aimed for 6lbs this time . After a lot of work ,most of it the logistics of building so large , I ended up with a model that looked reasonable and weighed in at 6 lb 13 oz , soo I was pleased with the result . I hope if flys well for him , should be a real floater . ...Continue Reading
Posted by Geoff Potter | Oct 03, 2016 @ 10:59 PM | 3,841 Views
Making some liners and other bits to complete some Taipan Tyro 2cc engines . Decided to chrome them . Built the power supply out of Strictly IC magazine ,works a treat ,battery powered , I litre tank will do up to 40 size if one is careful with the heat in the tank . Had to tig some of the cases ....Continue Reading
Posted by Geoff Potter | Oct 03, 2016 @ 10:03 PM | 3,738 Views
A few of the bits I give my granddaughter a hand to make for her school and now uni projects . We made the bits for the metal bits dress then she wouldn't wear it in the fashion parade so got her girlfriend to wear it . I was really upset ,didn't know she had a girlfriend that could make it look that good .
Posted by Geoff Potter | Oct 03, 2016 @ 09:41 PM | 3,793 Views
Just a little daunting until one gets started,then worked out fine !