Rob Lewis

Looking good

For a build you weren't even sure you were going to start its coming on fast. Excellent work, still watching with interest.

Posted by Simon Chaddock on 14/08/2014 16:03:26: After this I wonder how many pilots might be tempted to walk through the cabin to the cockpit with one arm hidden inside their jacket! We were joking about this around the briefing table earlier. Can't really add a comment on the subject, as we've been briefed at work to keep stum, you never know when a journalist may be watching. But its all a mountain out of a mole hill really...... Can't wait to see your Q4 take shape though Simon, watching with interest.

Hi Capt Kremen, You are correct. As with all planes we need the C of G within the correct range (18 - 30% MAC give or take) before we set off for obvious reasons. The Dash by design is nose heavy, so when we carry a smaller number of passengers that is why you see everyone crammed towards the rear of the plane and loads of empty seats up front. Its not helped by the change over recent years to luggage, people use to always check a bag, which with the hold at the rear of the aircraft, would help our trim. Nowadays everyone crams everything into a carry on bag, so we don't have the weight in the hold to balance us out. Re moving passengers, this usually happens because a passenger or 2 haven't turned up which moves the CG forward / aft, so we ask people to move to get it back into the allowable range. Rob

I tend to use different colour small cable ties, same principle. Although theres no ends sticking out with your solution so i may have to steal

Not guilty John , I'm based in Belfast, so 95% of my flights are to / from there. No problem Simon, I've been toying with the idea of building one myself for some time, most likely glow or petrol, but its probably one of those projects that will never get off the ground. Too many other projects filling the void.

Hi Simon, I fly these 'beauties' for a living. Was flying KKEV in the picture above a couple of days ago..... If you need any info or other pictures let me know and i'll see what i can do. Rob

Some great info there, thanks Jon. Will reconsider there use next when it is all back together again.

Talk about speaking too soon..... Just ran the engine again, was running like a champ with no problems at all and then BANG..... One of the conrods snapped around the big end and the thing ground to a halt, bending the crankshaft in the process. The joys of own designed homebuilt engines. Ah well, Dad's got the bits and its back to the machine shop for a while for a new crank and some stonger conrods. Hopefully only a few weeks time and a new improved engine will emerge. Edited By Rob Lewis on 05/07/2014 16:57:17

Bit of progress here, A couple of days ago i ran the engine on a test bench. Without thinking about it i mounted the engine upright on the bench (opposite to how its mounted in the model) and fired her up. Low and behold it run perfectly much to my Dad's delight...... So i was beginning to think that it must be a plumbing issue in the model, as all previous running was with the engine model mounted. I was just about to pack everything up and thought "i'll just try it inverted". This time i had the same problem as before, the same one cylinder failing all the time, even though it looked to be running extremely rich with copious amounts of smoke pouring from the exhaust. A bit of head scratching later and we decided that oil must be leaking past the piston into the dodgy cylinder and 'putting the glow out', hence all the smoke. The breather / crank drain in the backplate is at the top of engine when mounted inverted and so the oil would fill the innards before escaping through the drain. Cue some modification work. I tapped some nipples into both rocker covers (lowest point) to help drain the oil and cannibalized another engine that my dad had built and changed the piston and liner in the dodgy cylinder. At last i think i may have found the solution. For the first few tanks, the same cylinder didn't want to idle, but the replacement piston / liner was brand new and so it needed some running in. So far i've run around 10 small tanks through the engine and its getting better with every one. The cylinder hasn't dropped out once through the last 5 or so tanks, and i'm managing a nice slow idle. I don't have my tacho here with me so no figures, but after a bit of fine tuning back in the model and a couple more tanks and it should be in business. Thanks everyone for all the help / advise as always.

I've had the same problem trying to charge a single cell onboard glow pack with my generic 4 button charger. I fiddled with all the peak voltage drop, charging rates etc. but to no avail. I think some chargers just struggle more with the low voltages concerned. In the end i gave up with the charger for that purpose and converted a spare glow stick wall charger i had by putting a futaba plug on the end. Constant 1.2v 300ma charge, only downside is it takes around 26 hours for a full charge as the battery is a 7200, so you need to know well in advance of a trip to the field. If anyone knows of any chargers that decently charge single cells i would be interested.

Yep well done that man , all help much appreciated. I've been running it again today and always being indecisive, i don't think its overheating now. But its still a bit reluctant on the same cylinder. Definately a step in the right direction though. When you first start the engine it seems fine, as it warms up the one cylinder starts playing up again, so it must be a tolerance issue somewhere. When the one cylinder dies it is reluctant to fire back up again, and takes a fair amount of fiddling before it will burst into life. The cowling is just as big as the firewall, basically a huge saucepan with some cutouts.... No ducting, but all the running recently has been minus the cowling. I will cross that path when i get the engine going well as is. Not going to get much, if any time over the next 2 weeks to work on it but then i have a week off at my dads so hopefully will be some progress then.

I'm the guilty one with regards to the castor fuel Steve. The engine was brand new and sparkling when i got my hands on it. I was running it in on some 5% castor based fuel i had lying around. Today i have totally stripped the engine and theres no evidence of anything gummed up. All the running has only been in the last 6 months or so and it hasn't sat idle for more than a few weeks at a time with all the fiddling i've been doing. Taking what Shaunie said about a valve problem and the fact that the induction valve on the dodgy cylinder was weaker than the rest, i decided to replace the springs on all valves. Luckily i had some suitable ones in the spares box, and a couple of hours later it was ready to go again. The change is definately in the right direction, it's firing on both cylinders 99% of the time now with only the occasional drop, which lights up again without igniting the glow. Although it seems to be overheating now, hopefully some tweaking of the carbs will sort this out. Tomorrow will tell. Fingers crossed.

Cross posted with you Shaunie, Each set of followers have their own cams. I have turned the engine over by hand with the plugs out and compared the timing between the cylinders, and to the untrained eye the timings seem the same and the valves open and close at identical places in the cycle. That was the main reason i got it converted to twin carbs, so that i should have been able to tune out any fine differences in valve openings. Re a sticky valve. That definately seems plausible. Yesterday i run it with the rocker cover off to see if i could notice any problems, but as you'd expect the rockers move far too fast for me to notice any differences. I also noticed that the spring on the intake valve on the dodgy cylinder has slightly less strength than the others, but only by a small margin. I guess this could cause the valve to be slow in closing, causing a loss of compression / loss of mixture back out the intake. I have tried running it on each cylinder individually in the past. The good cylinder will fire and run consistently. The dodgy one will only fire with the throttle above idle, and can't maintain either idle or full throttle. The compression on the dodgy cylinder is probably about what i would expect from a normal ringed engine. The good cylinder has noticably less, but there is still a little compression there.

Cheers guys, The setup has a single tank but the carbs do have seperate clunks. That was the reason i swapped the fuel lines between carbs, to check the fuel was flowing. There isn't room in the model for 2 tanks, but in a few weeks i wil be visiting my father and can make use of his engine stand to run it so will try twin tanks then. The induction manifolds are a right angle about an inch long. They come out of the back of the engine through 90 degrees and then the carb is attached again at 90 degrees, facing forward, if that makes any sense. The pic below might show it better than i can describe. I don't have the tooling to create a shim, but its something my Dad could do when i see him in a couple of weeks, will add it to the list of possibilities.

Many years (15 or so) ago my father built a range of four stroke engines, singles and twins from scratch. At least one of the singles was in regular use with no problems. Fast forward a few years and i acquired and refurbished a Flair DR1, and intended to use a 1.5 Vee twin (25cc) that my dad had built. It had never been run but we fired it up quickly in his garage and all seemed well. It was built with a single carb, and while running it in i could never seem to get the cylinders balanced or running reliably, so my dad modified it to include a carb for each cylinder, which i hoped would cure the problems, unfortunately it didn't...... At about mid throttle, both cylinders fire perfectly and the engine runs like a champ. At both idle and full throttle one cylinder drops out. Always the same cylinder and same power settings. I have changed / adjusted everything i can think of but to no avail. Adjusted rocker clearences many times trying different settings Different fuel, higher and lower nitro etc Different plugs Swapped the carbs over between cylinders Swapped fuel lines incase it was a plumbing issue Removed exhausts incase there was too much back pressure Dismantled and reassembled engine a few times looking for any damage, air leaks etc. All of this made no real difference at all. The cylinder that is playing up has more compression than the other, but other than that they are identlical in terms of design, valve timing etc. It is mounted inverted and i have an onboard glow system for it. If the glow is off, the bad cylinder will die and stay dead. If i switch the glow on, at idle and full throttle, the cylinder will drop out for 5 seconds or so then fire for a few rotations than die again and so on. It sounds like a mixture problem, but i can richen the mixture until the needle falls off in my hand with no change, or screw it in till i starve it of fuel and it dies. Any ideas anyone? Rob Edited By Rob Lewis on 11/06/2014 00:24:18

I'd love one please.

I've been having a bit of a clear out....One mans junk etc etc. Hubsan Video glasses H510 Futaba 148's x 4 Master Airscrew 8x6 props x 4 HS81 servo gear sets x 5 Foam wheels Possibly faulty R617FS Rx Fusion NX85 Charger I'll probably find a few more things soon. I usually hoard everything but i'm realising i never use any of it. Rob

Better than the socks i'll get for xmas. Count me in please.