Geoff Potter's blog View Details
Posted by Geoff Potter | Aug 04, 2020 @ 09:29 AM | 4,894 Views
Was asked to make a return winch to pull back the tow up winch line for our OTime gliders , mainly cause we are all getting too old to be trudging up and down a glider field every launch. And it's an even bigger pain to have to do it for 5/6 winches when , with a bit of efficiency, we should only need one winch on the field anyway .
We came up with one that did the job , using a 12 volt Kenworth truck windscreen wiper motor matched to a Ryobi 4" angle grinder gearbox and a plastic hand casting reel mounted on it , and it worked quite well but it was destroyed in a fire where it was stored between uses .
So I had a popular model , car starter motor and when I pulled it apart , it had a 7to1 reduction planetary gearbox on the end of it . So I machined all the extra casting off it and made a housing to carry the shaft with a bearing on the gear box end and two bearings on the output end . I machined two 1"" blocks of Aluminium and put indent springs and balls with a centre shaft to lock them but still able to turn 90degees , another peice to mount the motor/ gearbox . Had to grind all the starter motor bits off the output shaft and down to 8 mill to suit the bearings I had . I bought a plastic reel and mounted it on a boss with a taper lock on the shaft much the same as one would use for aprop drive on an electric model , simple quick and easy . I bolted a 1"" square mounting leg on the bottom block and that fits into a square tube driven into...Continue Reading
Posted by Geoff Potter | Nov 05, 2019 @ 07:10 AM | 3,652 Views
Motor Cycle Pete sent this over to me as it had a pretty sad crank to crankcase fit , and asked me to grind and chrome and grind again back to size . I set it up in the grinder between dead centres and it took 5 thou off the diameter to clean up all the damage and out off round . There was no bush in the crankcase and the damage was pretty bad so I decided not to chrome the crank but make a bush for the crankcase and fit it to the slightly smaller crankshaft . I made a bush out of cast iron with a 2 thou interference fit in the crankcase hole that I bored on a jig I machined in the lathe . Pushed it in with the tail stock quill and some loctite , so I don't think it will move .
While it was still on the mandrel I bored the crankshaft hole in the bush and reamed it to size with a machine reamer and checked the size of the points boss and it was oversize so machined it back to the right size .
I then took it off the mandrel and held it by the boss in my smaller lathe and machined off the rear of the bush and cut a chamfer on it and tried the shaft , was a great fit .
I took it back over to Pete and he can put it back together for Condo , should be a very good engine ....Continue Reading
Posted by Geoff Potter | Mar 22, 2019 @ 10:21 PM | 4,057 Views
Hobby shop Bob my flying buddy , asked me to have a look at his 120 Magnum FS cause it wouldn't even fire let alone run . What a disaster , jammed valves , cam followers , ring , bearings were dreadful . Rust everywhere. Took ages to get apart , the gudgeon being the hardest to get out , I thought it would be the inner cam bearing as usual but came out quite well. Had to rebush both ends of the rod, make a new pin , grind the crank pin , re profile the cams grind the ends of the cam followers to clean up , reseat the valves after grinding the faces . Had to be careful with the valves when grinding them as the stems below the heads were well pitted with rust , but they seem quite strong so refitted them . The ring was stuck in the groove so soaked it in Chemcarb overnite and after a deal of fiddling I got it out with out breaking it , but made a new one anyway . Put it all together and it's a very nice engine now , runs and pulls very well , little worried about the carb as the barrel had a lot of rust type build up on it , but cleaned and polished and it does all the right things on the bench . Ugh , I've written all this and now I've lost most of the pics I took !!!!
Posted by Geoff Potter | Sep 13, 2018 @ 08:52 AM | 5,510 Views
My friend Motorcycle Pete , asked me if I could make a cylinder for a 500ccRudge engine . Apparently they are not available anywhere so I said I would give it a go . Started with a peice of 1020 mild steel round bar 165 mil diameter x 200 mil long and mounted it in a four jaw independent chuck with alive centre to steady it as it was a long way out from the chuck . I decided to do the outside shape and fins first while it was still solid , I figured it would be a bit more rigid and then bore it out after. I'm up to here so far . Had to take the cylinder up to my son Grants workshop this weekend as I didn't want to make a mistake with the positioning of all the head and crankcase mounting holes in relation to each other . He is very good on the computer and can set it all up and one just has to go to coordinates on the the read outs . I had to put a new power service to his workshop as well so we didn't get it finished but got some of the CNCmachining done , but still the fin area to do so will go up again next weekend to finish it . It's a three hr trip each way and knocks me around a bit these days , left home at 5am Sunday and got back at 12-30 am Monday morning , use to do it every day but not anymore ! Some pics from yesterday's effort , the NC makes life so easy ....Continue Reading
Posted by Geoff Potter | Jun 20, 2018 @ 10:54 PM | 5,952 Views
My friend Browny , had a bad day at our SAM Champs in Texaco this year , then at our Nats two weeks later due to wind when not needed . He crashed his Flamingo just after takeoff both times in the fly off of both events and bent the crankshaft in the original and then the replacement one that he had in a brand new engine which he fitted to the original engine .
He asked me if I could straighten them but after a couple of attempts it was a waste of time so I decided to make three new ones .
Was a bit difficult getting them out of the bronze bushed front housing and lost one bush because it was so badly bent but saved the housings and the new front end bush .
I decided to make them out of EN36A as it is reasonably tough in its normal state and turns well and wouldn't need hardening , so cut three pieces out of 11/4" bar . Faced and centred it and turned the thread/ prop area as it's hard to work up against the centre in the tail stock . Extended it out of the chuck and turned the rest of the straight shaft to 15 thou oversize , and did the grooves for the timer advance lock and the prop driver splines , also cut the prop nut thread as well and finished the prop area to size with a long tool but only needed a small clean up . Turned the outer diameter of the of the back end and then parted it off to suit the length of the crank pin . Then did the other two the same .
Transferred over to my smaller lathe as it has a collet head and I faced the back face and centre...Continue Reading
Posted by Geoff Potter | Sep 28, 2017 @ 08:02 PM | 6,500 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 | 6,298 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 @ 06:24 PM | 8,136 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 @ 11:51 PM | 7,818 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 | 8,278 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 | 8,006 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 | 8,083 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 | 8,373 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 .
Have updated my tank and power supply since 2017 , my son told me it looked like an environmental disaster area , also work holding has improved and is not so hit and miss as to where and what extra got plated .
The power supply is now 240 volt , just plug in , very convenient . The tank is bigger and easier to heat and control . Can go up to 15volts and 40 amps . Parts mounting is a lot better and so masking has improved . I can now do a lot more larger sizes of jobs . Is a whole lot easier to work with and control heat , current , and voltage .
I do spend a lot more time on jigs and fixtures , but have made them so that one top part can do a range of lower parts and sizes ....Continue Reading
Posted by Geoff Potter | Oct 03, 2016 @ 10:03 PM | 8,000 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 | 8,092 Views
Just a little daunting until one gets started,then worked out fine !