Merco 61

Hello, I,m not well versed with electric power.I have a nice old Graupner Cirrus and have been thinking of mounting a geared motor in the nose.I have a Kontronic Fun480-33 with gearbox and Jazz 40-6-18 esc..Would probably look for a 14x10 folder and 3 cell 2200 lipo.Am I likely to achieve safe self launching using this combination please ?

Thanks for all tips,much appreciated.Yes,did note the invisible circlip.The self tapper extractor worked a treat and gudgeon pin slid out easily. Whilst in Boots,I noticed a cheap DIY dentistry set,comprising a probe shaped like a shepherds crook ,and a little mirror and scraper.The probe,which is of very tough steel,was ideal for wrinkling out the circlip and cleaning out its groove.No use yet for the mirror.Shaft bearings both out without too much drama so should be plain sailing now.Thanks again

Hello, I,m in the process of renewing shaft bearings on an old but fairly good OS 120 Surpass .The gudgeon pin is firmly seized in the piston bearings.I stupidly allowed the liner to slide out so piston is no longer supported.Obviously liner cannot be replaced until gudgeon pin is removed.As only access is via hole at rear of crankcase,a rather difficult engineering challenge.I need to revolve the pin back and forth to release the seizure.I wonder if a suitable sized taper tap,sacrificial,could be carefully wound into the pin to give some turning power?The pin seems to rotate OK in the small end bearing.Any suggestions appreciated.

Very interesting thread,I thought post by Peter Christie was the definitive answer to a perrenial problem but......still not quite clear.A single cell nicad or nimh delivers 1.2 nominal(1.3 ish fresh off charge) reducing a bit dependant on length and thickness of plug lead.Plugs are sold usually for 1.5 to 2 volts,so,from the beginning,voltage is barely enough,from single cell.In my experience the degree of visible glowing varies a great deal depending on make and age ,from the same power source,2 stroke or 4.I,ve tried a number of glow sticks too,and do not trust them.Similar variations when using 12 volts through a power panel.Tom Sharp 2 talks about a 2 volt lead acid accumulator,ideal apart from risk of spills.In my impoverished youth,it was common to take Dad,s wood saw and cut a cell off the end of a car battery,with self tappers for terminals.Worked fine and never needed charging..My favourite at the moment,is a Ripmax 2v 4ah No.0PRP0204 sealed lead acid,about the size of a cigarette packet,fromSussex Models,I think about £7 plus a little charger and ammeter from the bits box.With this elementary rig,I no longer find it necessary to remove the plug for visible check on brightness,which was a regular annoying chore with the more sophisticated systems tried,especially in a cowled engine situation.I think I will stay with it from now on.

Thanks a lot for your help.Should now be able to proceed. Quite a significant model really,probably the first rc model to perform proper controlled rolls(1958) in competition,despite excessive dihedral by modern standards..OS 61 Blackhead going into mine. Cheers.

Hello, I,m restoring a much molested old Astro Hog from Flair kit.Tailplane is missing. Does anyone have the plan.I just need the basic tailplane dimensions and centre sweep angle,as it will be cut from sheet balsa. Hope some kind person can help.

To Cold Lazurus, Thanks for reply.I followed your instructions,worked first time,so great joy in the workshop.Very grateful to you.I hope that you will soon be warm and fully risen.

Thanks for all the replies.Cold Lazarus,yours is the answer I was really hoping for and set out exactly as all instruction books should be.I,m very grateful.Would you be happy to answer further programming queries via pm? Regarding some of the other comments,we all know that any spinning propellor is inherently dangerous,petrol ,glow or electric and I,be had my fair share of cuts and bruises over the decades,despite always taking the utmost care.Engines have to be carefully tuned and at some stage all have to be tested for maximum power,so need restraining.At our club,heavy steel yokes are provided at each starting bay,great,but all thrust loads are born by the tailplane only so not perfect.Thrown props,usually from big fourstrokes, is an undeniable hazard and I have no answer to this.Go to any full-size flying club and you will see 100 hp aero engines being swung by hand,the aeroplane is unrestrained and unchocked,the prop swinger trusting that the pilot really has got the mags switched off.I doubt if it is possible to achieve total safety with our models,all we can do is do our best to anticipate the possible dangers and learn from mistakes,ours and those of others.Which is why l recounted the two incidents.

I do understand the need to instruct the tx,it’s the route and sequence that I cannot find.This all arises out of two events that happened whilst testing models in the garden.Big scratch built Piper Cub,tail firmly roped to tree.Opened up to full power for a few seconds,tailplane joint failed,models shot forward,demolishing large shrub,cowl and uc.All over in an instant.Then a 1/4scale SE5,33cc petrol,tethered with four ropes at full power,throttle failed to operate when a ball joint came adrift.External simple manual switch easily accessible so no harm done,but a daunting moment nonetheless.Yes,a bit belt and braces,but I still want a kill switch for emergencies.

Thanks Ken,will look it up.Bucksboy,it is an opto switch connected between rx and electronic ignition box which,when triggered from tx,cuts power instantly,hence kill switch.I want it as a panic button in addition to normal failsafe.I fully admit to having a mighty struggle with most computer tasks,especially programming.So far,the system will not recognize the switch which is plugged into a spare rx input.

I am trying to operate an RC exp V2.0 kill switch from my Aurora.My computer skill is very low,Ive been trying fo hours,been through the book,no success.Can anybody tell how to do it please.

What about the lovely aroma of that big stack of fresh balsa and ply.? Or peeling open some new 10a blades and prepping the sanding blocks,cleaning off the building board and sweeping up in readiness to embark upon making the best one yet? I must have built hundreds of models over the last 65 years and the buzz at starting a new one has not lessened and,I hope,never will.

Thanks for your help, will look out for the helicoil ads on BMFA.Have found some JB Weld locally and will give it a try. Ace,I now remember why we dumped the horsehair blankets.

My latest unmissable eBay purchase and bargain.OS 120 .Exhaust bend loose in cyl head,closer examination seems to indicate it had been glued in.Threads in cyl head very worn.New head too expensive .Any suggestions for a high temp compound that might give a fix,albeit a once and for all,never unscrew again solution.

Hope this question is not interrupting the flow too much.I am about to swap out a much longer engine and replace it with my Laser v200.It will entail a1.5 inch spacer of some sort.Ive made up ally standoffs and long bolts in the style of many modern petrol engines,but it looks rather ungainly and I,m a bit concerned that I might be putting the Laser mounting lugs at risk in the event of a noseover into the rough.Would appreciate your views.Thanks.

Another way: find a piece of tubing to fit the hole(or slot) Then suck sufficient adhesive up into the tube,insert and blow.Flatten tube if for a slot.

Thank you,Anthony.A good solution.

Thanks Don,sounds promising,I,ll have words at the local full size club.I watched a TV programme about a German born doctor,living in UK building his full size Fokker Triplane.He used Oratex-or whatever it is called-,mentioned the brand several times,it looked exactly like our Glosstex.No mention of the make of adhesive to stick it to steel tube framing however. I once looked very closely at a dismantled Maule and was surprised that whilst the wing was entirely of rivetted aluminium,the fus and tail surfaces were covered in what looked like extra heavy duty Solarfilm,no weave,shiny and tight as a drum.

Thank you all for the very useful information.Ingenious solution,Gordon and wry final words appreciated.The hubris of turning up at the field with a bigger than normal scale job comes at quite a price though,doesnt it. A 10 metre roll it is then. I still like nylon and dope,cheap,strong but laborious.I recently used some very light close weave fabric from Boyces.Applied dry with Balsaloc,it heatshrinks beautifully and is even easier to wangle round the curves than Tex.Two light coats of dope was plenty for the Blackburn and free flighter used for the experiment and I really thought I had found the Holy Grail at last. Actually,I hadnt.It would seem,that after final heat shrinking and doping,there is no more shrink to be had.Dents from clumsy fingers cannot be removed by usual remedial heating and redoping does not work either.Pity,it looks nice and is very cheap. Jon,I have a question about mounting a Laser V200 on ally standoffs.Should I start a new thread?

Hello, Has any member built one? Mine just about ready for covering,so would like to know how much Solartex to buy.Plan is to use Linen overall,then paint for top surfaces.Wheels very expensive,so looking out for a secondhand pair. Model is the 80" one. Cheers.

Hello, I,m about to join the components forming the cabane on a 1/4 scale SE5.I,ve come up with a jigging system to hold the piano wire in correct register but still really need to bind some of the joints with fine copper wire for accuracy. My silver soldering is usually pretty good.Question:will the use of the copper wire spoil the joint? I,m using Easiflo solder. Just a domestic butane torch,no oxy. As this job has to be done with the cabane fixed to the fuselage,I,m quite apprehensive about a roaring blowlamp four inches from all that woodwork,so some wet towels will be in place as protection. It would really make my day if someone would tell me not to bother and that good binding and ordinary solder will be strong enough.

Raid the wife's washing basket and take two beechwood clothes pegs.Discard springs and use the four remaining wedges to insert between crankcase and prop driver.Lightly tap in tight with small hammer,then just keep tapping until driver is gently levered off.It will not gall the metal like a metal tool most certainly will. Heating will only help with an all aluminium driver,many have a brass bushing so heat not so effective.Emphasise,just tap the wood,not any metal.

Hello, onetenor,I dont think anyone will argue with anything you have written,certainly not me,a good analysis and sound theory I,m sure.The threads on the crankshaft are in good condition.I,m doing my utmost to keep them that way.I,m using nothing more than two ordinary plain nuts at the moment,as even SC ones are about £12 per pair and Ive lost two sets to date.A nylon spinner is fitted-for the starter and as a loose nut catcher. I think a spinner with an ally backplate might help too. With compression reduced and needles about where they should be,the prop no longer flys off but once in a while there is a squeak and the prop shifts on the shaft,just a little,when starter applied.Then essential that all is re-tightened or all will come loose at next attempt-guaranteed.The neighbours are used to my engine noises but are getting fed up with the foul expletives when this happens.Do you think there is any pssibility that the powerful starter is part of the problem? How do you set the prop to perform the nifty backwards flick that Jon does in his video?Thanks a lot for your interest everyone,I,m sure that all the good gen is appreciated by all four stroke users.

Graeme, I,m with you all the way other than the 400 shifter.Too much leverage for my nerves.Jon says a 250 mm spanner which is a lot more than I,ve been using.In general terms I,m not at all convinced that a lock nut is guaranteed to work in this context,especially,as you say,when they come off as a jammed pair and can be replaced the same way.Where is the locking?Also I dont like the click when you spanner them apart.Tortured threads? I,ve binned the TT ones anyway,not enough thread on female to do any good,but sufficient perhaps to damage crankshaft.I was going through my prop drawer.The three blade 14x7 Graupners and MK fibreglass 13x10.5-all glow props- are all drilled for 4 bolt fixing.Is this telling us something we,d rather not hear? Sorry for repetition-I did some bench tests.The breakaway point was between prop driver and prop every single time,so in the absence of a bolted hub,some weapons- grade lateral thinking is called for,not just this engine but any biggish four stroke.I,m going to dig out a torque wrench and find out the poundage were putting on these shafts.

Hello, Will try to respond to your posts as briefly as I can.Tried both alternative prop nut fixing order.No difference.Swapped over to SC, nuts,no improvement.De-rated engine with shims,ordinary 5/16x32 nuts now remain in place.Engine is now rather nice.Even runs on straight castor which I use for ancient two strokes.Supplied plug is stamped Japan RF.I,ve tried some cool Rossi short reach,but to no advantage,so back to OS F.Some extra care with tank and more messing about with washers including changing steel prop washer for a very thick alloy one has brought an improvement.I will get there, determined to.Seems undeniable that most model 4st will loosen their prop nuts if provoked by lack of attention to detail at startup.Surely,the more powerful the engine,the more critical this becomes.The TT has proved that a high compression engine on startup delivers too much torque for a 5/16" nut to contain. when carb is out of adjustment.An analogy:electric lawnmower blade only retained by spring-castellated grip washer and plain nut but has electronic soft start. 150cc four stroke mower has only a plain bolt but the main shaft is protected by a huge boss made of friable cast alloy designed to shatter if (when) you hit something,thus protecting main shaft.I often use the big Super Tigre 2strs and have never felt threatened,likewise petrols,big softies really.I have been hurt by tiny.25 diesels,cut by Comp Specials,and nearly emasculated when kneeling before a Laser,accidentally starting it full throttle when the prop flew off and cut me acroos both thighs.OS 61 and 90 have come loose-the list goes on.I,m sure Jon will tell us Laser.s rationale for safe prop retention.I keep looking at the video of the 120 so the kid,s inheritance is under real threat. Re. old Enyas 35s,I,m pretty sure mine came with two cyl heads,one for straight and one for up to 10% nitro.Air bleed carbs on these and early Mercos were easy and worked well.