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RE: Poulan 25 from FL trimmer - 9/16/2005 1:18 AM   
RysiuM



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ORIGINAL: diablo_r
do you have a web link or something for the vlach ign, it sounds interesting as I wanted to try electronic but its $200 over here, thats 10 engines!!


Pe from MVVS.NL has it in stock for 123.81 Euro (including VAT - UK is part of EU, so you pay it).

You may also try Jenny and Paul from JustEngines - thy are in UK and very nice and friendly to deal with.

One more thing about Vlach is safety shut-off. If you leave the ignition powered for more than 90 seconds without moving the prop it will shut itself off. It's just safer in the shop. I have always buzzer in the circuit, so when ignition is hot, I can hear it well.

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RE: Poulan 25 from FL trimmer - 9/16/2005 1:26 AM   
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Status: offline 		cheers, I bought my last saito and all my engine bits from just engines but could ony find the MVVS with the ign, not the ign unit by itself. I mght call them tomorrow!

Rich

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RE: Poulan 25 from FL trimmer - 9/16/2005 2:24 AM   
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ORIGINAL: diablo_r
could ony find the MVVS with the ign, not the ign unit by itself. I mght call them tomorrow!


They say, they do parts too. Let me know what you find. I'm also looking for spare Vlach ign (but not decided to spend over 100 bucks yet). I got my MVVS gas from justengines - was much cheapper and faster than trying to buy it here. And very friendly to talk to.

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RE: Poulan 25 from FL trimmer - 9/16/2005 11:50 PM   
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Status: offline 		well today I got angry with power tools

Seeing as the original coil mount was now no good I stripped the engine to remove all metal that is not needed. This included the lower crankcase which every bit possible was cut/powerfiled off, and the cylinder which I mounted in the lathe and turned all the draft off the top 5 fins with a rounded off parting tool. I left nothing it did not need! I also cut the transfer passages in the piston under the gudgeon pin area. I also wanted the weight and complexity of the throttle bellcrank off so I made a new inlet manifold to turn the carb about 50 degrees round to allow direct connection of the throttle snake to the throttle am on the carb.

Total weight of the new glow or elec ign version, including exhuast, prop adaptor, carb, bellmouth, mount and all bolts is 1220 grams. Add 166 grams for 2 3000 NiMh cells for onboard glow and its pretty light!

I've put the pics on so you can see, I'll test it tomorrow hopefully. I need to sort out the carb pressures too but need to make a test gauge first!

Cheers,
Rich

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RE: Poulan 25 from FL trimmer - 9/17/2005 12:49 AM   
RysiuM



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ORIGINAL: diablo_r
Seeing as the original coil mount was now no good I stripped the engine to remove all metal that is not needed.


One thing I see you can cut off is the original fuel tank mount. You use it for your upper (in inverted) mount. If you can change the mount you can use smaller possts (under the fuel tank mount) drilled and threaded (i.e. M4). See the picture How I cic the back mounting holes - the original fuel tank mount is already cut off Just few grams less



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RE: Poulan 25 from FL trimmer - 9/17/2005 12:52 AM   
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Status: offline 		One more thing - I didn't do much cutting in lower case and cylinder as I didn't know how strong shoud it be. So I left all pieces (kind of fins) in lower case just to make sure it will not blow up or crack when running.

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RE: Poulan 25 from FL trimmer - 9/17/2005 12:58 AM   
diablo_r



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Status: offline 		well if it goes pop, it goes pop! Its kind of a development engine anyway so if it does not go pop I've not pushed it far enough!

I have already drilled and tapped M4 those bits you talk about but did not have time for making another mount today so stuck with the one I already made. Another job for the future.

My main worry with the lwoer crnakcase would be flexing of the case making the bearings go tight but using my highly trained engineers eye I reckon it has enough ribs to keep it all in line. Only more flihts will tell though, but first I've gotta get it running on glow. I emailed Just Engines too to ask about buying the ign, if they cannot supply I'll buy one from Holland.

Cheers,
Rich

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RE: Poulan 25 from FL trimmer - 9/17/2005 1:13 AM   
RysiuM



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ORIGINAL: diablo_r
Total weight of the new glow or elec ign version, including exhuast, prop adaptor, carb, bellmouth, mount and all bolts is 1220 grams.


Are you sure about that? 1220g = a little over 43oz.
My rough cut engine including original carb and adapter, custom muffler, mount and prop adapter is 37.5 oz. See the post #15 in Step by step converting Poulan 25cc FL trimmer

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RE: Poulan 25 from FL trimmer - 9/17/2005 1:40 AM   
diablo_r



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Status: offline 		its the exhaust that makes all the difference, the one I have right now is all steel hence the 5oz weight difference.

Maybe I'll get sorted out and either get a tig, or buy a wacker engines one.

Cheers,
Rich

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RE: Poulan 25 from FL trimmer - 9/17/2005 1:46 AM   
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Status: offline 		forgot to ask, how much does the wackerengines muffler weigh...?

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RE: Poulan 25 from FL trimmer - 9/17/2005 1:53 AM   
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Status: offline 		Hi,
Nice trim job. Is the notch in the thrust face of the piston stock?

Dave



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RE: Poulan 25 from FL trimmer - 9/17/2005 2:15 AM   
RysiuM



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ORIGINAL: diablo_r
forgot to ask, how much does the wackerengines muffler weigh...?


That's the one on the picture


This one has not cut engine holes yet becuse I wanted to do it myself. Also the weight does not include 2 screws that are about 1 oz. So the final weight is about 4.5oz including bolts, but if you can get tytanium bolts you will save some weight.

I found, that actually the original gutted muffler with drilled two 14mm holes in outer case weight the same and performs the same - just looks ugly. And both are loud anyway. But I would rather have some long aluminum tube instead that would sound like Harley. I'm going to make or order something like that for my Wilga.

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< Message edited by RysiuM -- 9/17/2005 2:16 AM >

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RE: Poulan 25 from FL trimmer - 9/17/2005 11:08 AM   
diablo_r



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Status: offline 		ah, that explains it. The exhuast I have right now is 313g (about 11oz) and the wacker engines one is 110g. With one of those mufflers and a bit of tweaking I might be able to get this under 1kg, that would be an achievement.

Best get one order next week then!

Dave, the piston as standard is circluar at the base, I have cut all the notches. The front one for the intake timing, the side ones to open the transfers with the piston at BDC.

Cheers,
Rich

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RE: Poulan 25 from FL trimmer - 9/17/2005 8:56 PM   
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Status: offline 		Hi Rich,
That intake notch really is large. How many degrees is the intake duration? My stock blower engine is 132 degrees duration or 66 degrees before TDC. The tranfer notches should help a lot.

Dave

< Message edited by davewallace -- 9/18/2005 6:14 AM >

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RE: Poulan 25 from FL trimmer - 9/17/2005 11:51 PM   
diablo_r



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Status: offline 		Hi Dave,

I've read some of your other posts, you've played with a few engines! Your numbers do not make sense though, do you mean your blower is 132 degrees duration...? 66 deg BTDC and 130 total duration do not add up.

As standard my engine had 122 degrees, but the key numbers are the port time area and the port angle area, both of which were woefully low, in the end its a mass production 6000rpm trimmer engine not intended for turning a 16" prop at 9000rpm

To get it to those revs it needs a load more transfer, a bit more exhuast and a mid amount more inlet. Sorry for the SI units, but as standard the engine runs a PTA of 0.000063 sec-cm^2/cm^3 but given Jennings data for 8000rpm it wants to be 0.00014 to 0.00016 IE its half what it should be. The port angle area as standard is 3.01 and it should be 6.7 to 7.7, again half. Well I cut the port as high as I could without it exposing the inlet to the cylinder over the top of the piston at BDC, but that only gave 126 deg duration, PTA of 0.0001 and PAA of 4.5 so the next step was to cut the piston skirt to increase the figures, so now it runs 156 deg duration, 0.000138 PTA and 6.6 PAA. Its on the low side still, next step will be to widen the port to get the figures up a bit more but seeing as a reed valve motor runs 180 deg inlet timing the size of notch in the piston is not so critical, the thing that is important is the port is open long enough to let the engine take as much as it wants to.

Of course there is more than one way to skin a cat, or even tune an engine, this was just my take on this engine and I'll probably port the next one a little different, ie more area and less duration. The disadvantage of large area ports is obviously the lower air velocity which in itself can cause problems with fuel falling out of suspension etc etc.

Cheers,
Rich

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RE: Poulan 25 from FL trimmer - 9/18/2005 6:12 AM   
davewallace


 

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Status: offline 		Hello Rich,
Thanks for pointing out my typographical error. You were right, it should have been 132 degrees. I didn't mean to put you into attack mode. I take modifying my engines seriously and don't consider myself playing with them. It won't happen again.

Dave

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RE: Poulan 25 from FL trimmer - 9/18/2005 11:51 PM   
diablo_r



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Status: offline 		Sorry Dave, my coments were meant only as a compliment to you and your obvious experience.

Cheers for the info on Mufflers Rysium, I ordered a wackerengines one today so should have it in a week or so. I also talked with a couple of electronic wiz's at the patch today and between us we are going to have a go at building an electronic ign, maybe even PIC, with a nice small coil specifically as light as we can. Will keep you updated.

Cheers,
Rich

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RE: Poulan 25 from FL trimmer - 9/18/2005 11:58 PM   
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ORIGINAL: diablo_r
Cheers for the info on Mufflers Rysium, I ordered a wackerengines one today so should have it in a week or so.

One more thing about this muffler. I have two of them. It is designed so tubes are screwed in to the muffler body. I tried different things and still didn't sucseed with keeping them in place. Even muffler-pipe sealer doesn't keep them in place and tey are always shaken loose. A think the second one I will just weld in place (maybe this 'magic rod' that can weld aluminum).

quote:

ORIGINAL: diablo_r
I also talked with a couple of electronic wiz's at the patch today and between us we are going to have a go at building an electronic ign, maybe even PIC, with a nice small coil specifically as light as we can. Will keep you updated.


Please do.

Thanks
RiysiuM


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RE: Poulan 25 from FL trimmer - 9/19/2005 12:07 AM   
diablo_r



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Status: offline 		I've heard about the alu welding stuff, you can buy it here but I've heard that with an engine runnign in a cowl it can get hot enough to remelt the magic stuff and the pipe falls to bits. I'll see when I get mine but maybe I'll find a way to lockwire or pin/grubscrew them in place.

Cheers,
Rich

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RE: Poulan 25 from FL trimmer - 9/19/2005 12:22 AM   
Antique



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Status: offline 		The magic stuff melts at 750F and there is no penetration..Think of it as solder...It should work OK if the tubes are screwed in first..

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RE: Poulan 25 from FL trimmer - 9/19/2005 12:28 AM   
RysiuM



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ORIGINAL: diablo_r
I've heard about the alu welding stuff, you can buy it here but I've heard that with an engine runnign in a cowl it can get hot enough to remelt the magic stuff and the pipe falls to bits.


The Pipe and muffler sealer is rated to 2000F, so it is not affected by the heat, but it brakes on vibration. It cures to the solid hard mass and the engine vibration and expanding aluminum in the heat brakes it loose.

I don't think these pipes will get hotter than 300 - 400F. Aluminum is good conductor so the heat is distributed through the entire muffler and the surface is cooled quite efficient. I read somewhere that the rod is good up to 700F so if it flexes and expands together with aluminum it should be OK. The entire load is carried through the thread anyway, I just need something to keep the pipes from unscrewing in vibration.

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RE: Poulan 25 from FL trimmer - 9/27/2005 12:36 AM   
diablo_r



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Status: offline 		Hi Rysium,

I've sorted mine with 35% glow fuel, 65% methanol and spent last weekend flying it. It ran great but really needs a 17 or 18x6 on my Pitts for a bit more thrust. Vertical is not bad, but not unlimited. I did the full aero routine with it and the engine ran faultlessly so I'm pleased with that. Only thing is I did the psiton side cutouts under the gudgeon pin and it lost 300 revs. I'm going to put a std pitson back in sometime and try it but I'd leave that mod if you've not already done it as I don't think its a wise one.

Also got the wacker engines muffler today so thats fitted, another 8oz off the engine. Total weight of the glow version is 920g now.

Next job is I'm developing two electronic ignitions for it, one fixed timing and one variable. Should have the fixed one running by weekend and a few weeks for the variable one.

Just as a side note when I got the muffler it had a note in saying if you send it back they will weld the pipes into the muffler for free, you jsut pay the postage. I have drilled and lockwired mine, and the mounting bolts, to stop them coming undone.


Let me know how you are getting on. I got another 2 engines the same too so will get into tuning them soon.

Cheers,
Rich

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RE: Poulan 25 from FL trimmer - 9/27/2005 1:33 AM   
RysiuM



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quote:

ORIGINAL: diablo_r
I've sorted mine with 35% glow fuel, 65% methanol and spent last weekend flying it.

Wow, pure methanol - no gas. It must kick the but. Did you need different carb for that? Engine needs about 2 more fuel in the muxture than if you use gasoline. Did it start by hand?

quote:

ORIGINAL: diablo_r
It ran great but really needs a 17 or 18x6 on my Pitts for a bit more thrust. Vertical is not bad, but not unlimited.

What's the weight of your Pistts? If you can turn APC 18x6W at 8k rpm, it should pull around 12 lb unlimited.

quote:

ORIGINAL: diablo_r
Only thing is I did the psiton side cutouts under the gudgeon pin and it lost 300 revs. I'm going to put a std pitson back in sometime and try it but I'd leave that mod if you've not already done it as I don't think its a wise one.


That's a surprise. If you have other engine available you can try to replace just the piston with original sleve and check if this cut is the reason. I swapped piston/cylinder between engines and in short time therte is no much difference in there. They are manufactured with the accuracy that they wouldnt feel that. It's hard to believe that opening transfer ports does bad thing for the engine.

quote:

ORIGINAL: diablo_r
Next job is I'm developing two electronic ignitions for it, one fixed timing and one variable. Should have the fixed one running by weekend and a few weeks for the variable one.

I just ordered VLACH from Pe for my experiments. I have one prop hub prepared for magnets so this willbe the one for electronic ignition.

quote:

ORIGINAL: diablo_r
Just as a side note when I got the muffler it had a note in saying if you send it back they will weld the pipes into the muffler for free, you jsut pay the postage. I have drilled and lockwired mine, and the mounting bolts, to stop them coming undone.


Did it work? 'Whacker' might not like to see my muffler - faar away from the new look It's all dirty in burned oil and tailpipe sealer. Welding this thing will not be easy. I will try set screws placed in the thread.

quote:

ORIGINAL: diablo_r
Let me know how you are getting on.


I was busy lately restoring Kyosho Cap 232 (40 size), so I didn't grab the Dremel yet. But when Vlach ignition comes there will be no more excuses for me

RysiuM

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RE: Poulan 25 from FL trimmer - 9/27/2005 11:24 AM   
diablo_r



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Status: offline 		opps, sorry to get you so excited, it was 35% glow, 65% petrol, my mind must have been somewhere else when I typed that! I've got 2 gallons of straight methanol on order though so will have that soon.

I have not run the muffler yet, maybe at the weekend I'll fly it again but lockwire should be fine until I save up for a TiG!

Pitts is just under 12lbs, and on the 16x8 APC at 8600 it pulls 13lb thrust when I measured it, so a 17 or 18x6 should be 15-16lbs thrust I would guess. I'll get one ordered tomorrow probably ready for weekend.

The other thing I did to my muffler was put a metal drift into the inlet hole and hit it with a hammer, mushrooming the top of the pipes thread to stop them coming out. A bit extreme but I don;t want them coming out

Cheers,
Rich

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RE: Poulan 25 from FL trimmer - 9/27/2005 5:07 PM   
RysiuM



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quote:

ORIGINAL: diablo_r
opps, sorry to get you so excited, it was 35% glow, 65% petrol, my mind must have been somewhere else when I typed that! I've got 2 gallons of straight methanol on order though so will have that soon.


So I guess it keeps running without power on glow, right?


quote:

ORIGINAL: diablo_r
I have not run the muffler yet, maybe at the weekend I'll fly it again but lockwire should be fine until I save up for a TiG!


Even if I get one, I don't have room in my garage for it anyway I need smaller house and bigger garage

quote:

ORIGINAL: diablo_r
Pitts is just under 12lbs, and on the 16x8 APC at 8600 it pulls 13lb thrust when I measured it, so a 17 or 18x6 should be 15-16lbs thrust I would guess. I'll get one ordered tomorrow probably ready for weekend.


I have MVVS 1.6 on Powerline Hobbies Edge that weights 11.5 lb dry (12 lb full). APC 18x6W at 8300rpm i have enough thrust for unlimited vertical. However APC prop seems to be to heavy for fast throttle response. Mejzlik 18x6 is on it's way .


quote:

ORIGINAL: diablo_r
The other thing I did to my muffler was put a metal drift into the inlet hole and hit it with a hammer, mushrooming the top of the pipes thread to stop them coming out. A bit extreme but I don;t want them coming out


Sure. . Keep me posted about the piston sleve tests.

RysiuM

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