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fiery 12-09-2012 01:56 PM

Tadpoles
 
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Has anyone ever seen one of these?

Are they still available?

A running report from an owner, not just a collector, would be most appreciated.

greggles47 12-09-2012 02:50 PM

RE: Tadpoles
 
Derek,

I haven't seen the Tadpoles, but Ian Russell (Rustler) is a regular contributor on Barton CL site. It would be worth asking him the question.

I have one of his Olly Tiger replicas, an absolute gem of a motor.

Regards

Greg

ffkiwi 12-09-2012 04:45 PM

RE: Tadpoles
 
Yes-I have one (as you'd expect) and yes-its rather nice! Came with two tanks-one metal one plastic, and is a very accurate representation (on a smaller scale obviously) of the Frog 50 Mk1-and with a LOT better handling than the original. Quite pokey too-a lot better than the similar sized ED Baby 0.25cc replica-though the latter is a joy to run. So far mine is only bench run, and has yet to find itself a model home-but I'm leaning towards either the Ron Warring 'Titch' from ca 1953 or the Skyleada 'Point Five'..........
.......I'm just back from the flying field after a morning of mixed success trimming-pre Nats checking of some of the fleet-and in keeping with the forum, am pleased to report the Doonside Elfin 149 continues to start and run impeccably. The 'Midi Pearl' that it's in however, needs some minor fettling-a snid more left thrust, and a gnat's foreskin less right rudder to sort the climb out. On the plus side the first of two 'Y-Bars' had its maiden flight this morning, a mere 8 oz on a Cox Space Hopper-which also had its first run (at least of my ownership).....~=*!! reed valves..............flick it forwards-starts backwards, flick it backwards-still starts backwards..........required the starter to sort it out-but once running, took the Y-Bar skywards in the classical corkscrew pattern with no adjustments whatsoever required-a genuine 'flew off the bench' job.

....now give me a bit of time to have some luch, clean up etc-and I'll be back with some figures on the Tadpole..............

ChrisM
'ffkiwi'

ffkiwi 12-09-2012 07:27 PM

RE: Tadpoles
 
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Well I've just run mine again on a Cox 6x3 yellow nylon. Still runs hot, and quite a lot of vibration. Its not a Mills 75 by any means in terms of starting-but at the same time-completely normal diesel responses-it's quite critical for optimum compression setting-and lets you know very quickly when even slightly over-compressed-by labouring quite markedly. Needle is not of the 'precision adjustment' variety (nor was the original Frog 50!)
Best revs at this stage on the 6x3 (which is the recommended running in prop) were 6700rpm on Model Technics D1000 homebrew. It could not run out a tank before overheating and stopping-so there is still plenty of running in to do-and Ian's recommended fuel mix (very high in castor) is clearly needed for this phase. [see scan of instructions attached]-I'll mix some of that up, and hopefully do a few more runs tomorrow.

ChrisM
'ffkiwi'

PS Even at 6700rpm there was plenty of thrust coming off the 6x3 Cox-certainly enough to fly a suitable small light model.


fiery 12-09-2012 09:08 PM

RE: Tadpoles
 
Pretty impressive for a biggish fan, on a 1/4 cc engine. Thanks Chris.

ffkiwi 12-09-2012 09:55 PM

RE: Tadpoles
 
Fiery-it's about 2 years since I last ran it-and it had a DC 5-1/4 x 3-1/2 prop on it when I dug it out today. I vaguely recall it was quite a bit faster-not surprisingly-but harder to start- on that one. I'll make up some fuel 'according to Rustler' and do some more running. I have quite a range of suitable props. I don't think I've run it on the Cox 6x3 before-and this prop is a heavier load than some others. A few more tests will establish what it's happiest on. My VA Bambi is very happy on the same 5-1/4x 3-1/2 prop (originally produced for the 0.75cc DC Bantam!) so it is not inconceivable that the little Frog with 2/3 more displacement might turn something a bit bigger with authority........

ChrisM
'ffkiwi'


ffkiwi 12-10-2012 01:02 AM

RE: Tadpoles
 
A nasty discovery made this evening-which may have a good outcome for the wee Tadpole down the track-the Cox yellow 6x3s are badly out of balance as moulded-I had vibration problems with two separate ones today-one on the 'Y-Bar' mentioned above and one on the Tadpole. Since I don't recall vibration previously being an issue with the wee thing when last run about 2 years ago, my nasty suspicious mind started thinking 'what's so different today?' ........and a check on the balancer revealed the problem. Not just a finger balancer-which is how I routinely balance them, but one of those good rolling wheel Dubro ones. The problem is mainly-but not totally-an out of balance hub, though one blade needed a bit of lightening as well. Fortunately I have a small supply of tungsten putty-which is ideal for balancing........

ChrisM
'ffkiwi'

ffkiwi 12-10-2012 12:33 PM

RE: Tadpoles
 
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OK-one day later and I've just run it up several times on the now carefully balanced Cox 6x3-vibration is still present-so it may be a wee bit of a shaker. I have gained a few hundred rpm though-but whether this is due to the reduced vibration or simply a consequence or more running time is a moot point. 7000+ on a 6x3 would put it up there with the VA .4cc Mills and VA Kalper .32 for performance-so the little Tadpole is punching above its weight!
I haven't made up any of the specified fuel yet-will be interesting to see how that compares with my Model Technics D1000 mix. I'd expect the engine to perhaps sound happier-but produce less revs, on this mix (see previous post of scanned instruction sheet for the recommended fuel mix)
Here's some pics-on a rather cool Wellington morning..........

fiery 12-10-2012 01:11 PM

RE: Tadpoles
 
Chris

I checked with Ian Russell (aka "Rustler Engines").

Unfortunately he no longer has any Tadpoles. They have all swum off. A pity. I would have bought one as a Xmas present to myself after reading those figures!

I do have a current list of Rustler's available engines and spares. The list on Barton is very out of date. I am reluctant to post it up on this forum as it may breach RCU rules. I can email it to anyone who may be interested.

If any reader wants a copy of the list, kindly PM me your email address.

ffkiwi 12-10-2012 02:51 PM

RE: Tadpoles
 
As we both know now to our cost-you have to get in quick with these little gems-whether they be Benno Schlosser's, Arne Hende's, Dave Banks'/VA or Ian Russell's ones-supply is strictly limited-and 5 or 10 years down the track you're kicking yourself for not getting one when you had the chance....

I've had the Tadpole since about 2000 I think-along with a 0.8cc Oliver Tiger Cub that also emanates from the same stable-judging by the style of the box artwork.

more prop tests to follow..............now having a small plethora of checked and re-balanced props to play with.............

On reflection I was probably unduly harsh on the starting properties yesterday(probably because it was a bit gummy and clogged up from previous runs 2 years ago)-while it certainly isn't a first flick starter, I didn't mean to imply that it was difficult to start. It responds well to finger choking (the suction is enormous-you can see the fuel level in the tank drop when you choke it), a couple of drops in the intake and a miniscule exhaust prime.

ChrisM
'ffkiwi'

j.hiner@comcast.net 12-10-2012 04:21 PM

RE: Tadpoles
 
Vintage diesels tend to vibrate. One way to reduce vibrations is to use out of ballance props with the heavy blade up when the piston is down. This has worked for me. I paint the heavy blade red so know which blade is heavy. Jack

ffkiwi 12-10-2012 05:11 PM

RE: Tadpoles
 
deleted after edit

ffkiwi 12-10-2012 05:12 PM

RE: Tadpoles
 
A carefully balanced prop has reduced vibration to a comfortable-as opposed to an unnoticeable-level in this case Jack. I think the deliberately unbalanced prop approach (I have tried it) works better on the larger long stroke vintage diesels with relatively heavy pistons. Then there is the simple and well recorded reality that some engines have 'vibration bands' corresponding to a few thousand rpm or so somewhere in their rpm range. Within this they vibrate badly-propped above or below this band they run smoothly. Then there is the utterly counter-intuitive observation that some engines where there is no attempt whatsoever at any form of counter balancing-and with heavy pistons to boot-run quite smoothly-I give you the ED Bee, Elfin 149, DC Spitfire and Sabre and the Frog 100/149/150s as examples. Go figure...........!

ChrisM
'ffkiwi'

Recycled Flyer 12-10-2012 06:20 PM

RE: Tadpoles
 

Quote:

ORIGINAL: ffkiwi

Then there is the utterly counter-intuitive observation that some engines where there is no attempt whatsoever at any form of counter balancing-and with heavy pistons to boot-run quite smoothly-I give you the ED Bee, Elfin 149, DC Spitfire and Sabre and the Frog 100/149/150s as examples. Go figure...........!

ChrisM
'ffkiwi'
I am going to run with the idea that heavy pistons, heavy flywheels, solid blocks all tend to resist movement.

The piston acceleration from rapid onset diesel ignition is resisted better with a heavy piston, a heavy full circle flywheel stores energy better between cycles and a solid block absorbs the vibrations.
And the use of large prop, low revs and the old less powerful fuel mix of 33% of each helps too.

But surely all of these old designs don't make 'that' much power in order to create the thump in the first place?

So, if you'could' push any of the above engines to say 18 000 rpm and beyond, would they then start to vibrate badly?
Would they then be really better off with proper counter balancing?


ffkiwi 12-10-2012 06:39 PM

RE: Tadpoles
 
Put a flywheel on one and see..........

CJM

AMB 12-10-2012 06:49 PM

RE: Tadpoles
 
Some wheres in my parts bin is a "flywheel" the intended use was to add weight to balance the plane it replaces the front drive washer and front is recessed to get the prop nut on
and they are heavy can get in various weights 1 oz not uncommon might work to reduce vibration martin
way too big for the wee ones at least an inch in diameter 1/4 inch bore maybe 35s and up

Recycled Flyer 12-10-2012 06:53 PM

RE: Tadpoles
 
Hi Chris,
I don't have any of the engines that you listed but I have run modern marine engines - they don't seem to mind flywheels (not sure what that proves though.)

But I have an old PAW19 DS that had a full circle flywheel that used to vibrate quite badly and after grinding off the cheeks as an attempt to balance it, and it was much better.

Do you think that adding a flywheel makes this better or worse?


AMB 12-10-2012 07:05 PM

RE: Tadpoles
 
on the front flywheel thing it could be ground down on one side to unbalance you would have an external counter weight with getting it in proper position on shaft martin

ffkiwi 12-10-2012 07:17 PM

RE: Tadpoles
 
(1) I meant put a flywheel on in place of a prop and run one at 18,000 plus..........and see what happens...........

(2) I'll bet your modern marine engines have very light pistons, massive blocks, and heavily counterbalanced crankshafts............

(3) Even people like Cox got it wrong from time to time-the TD15 and it's successors were notorious for vibration in their day when propped for peak revs-'shake timers to bits' was the expression used by some of my older mentors who did use them. The answer was to grind both flanks of the crankweb carefully to increase the degree of counterbalancing. The magic figure-according to the books, is balancing 60% of the reciprocating weight..........

(4) OS went to the extent of using counterbalanced prop drivers for a while in the 1960s on the Max-15 and 19-did it work? I don't know-they stopped doing it........

(5) Anyone remember the famous K&B 45 greenhead-arguably the first 'proper' pattern engine? It had a backplate mounted counterbalance driven from the crankshaft to improve smooth running

(6) The russians-no fools when it comes to miniature IC engine design-even went as far as drilling holes axially around the circumference of part of the shaft to counterbalance the weight lost from the intake cutout.........and this was in a cheap F2D training motor.....the Typhoon.


....as for me, all I will say on the flywheel aspect is that I have several engines fitted with heavy brass spinner nuts for CG purposes-(and one is your beloved PAW19 DS!)-and these engines seem to start easier and run smoother than those without-but I've never systematically looked into it.

ChrisM
'ffkiwi'

AMB 12-10-2012 07:38 PM

RE: Tadpoles
 
Chris I 2nd your observation on the heavy brass spinner nuts and noticed the same thing easier hand flipping to start and reduced vibration martin
think that heavy spinner gives you inertia on the flips

ffkiwi 12-10-2012 08:00 PM

RE: Tadpoles
 
I think you're quite right Martin-but there must be a point somewhere where the excess weight starts to slow the engine. I suppose if one was anal, had a lathe, plenty of brass and a lot of spare time, one could machine up a whole raft of heavy spinners, in increments of say half an ounce difference, and then, with all other elements-fuel, prop, temp, etc constant, run a series of tests..........

ChrisM
'ffkiwi'

fiery 12-10-2012 09:57 PM

RE: Tadpoles
 
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I will also say the same.

I put a Harry Higley brass "heavy hub" on a .46 powered pattern trainer for CG purposes. I hid it under a 2 3/4 " diameter spinner. Increased smoothness and reliability of the engine at idle was noticeable. I noticed no difference in throttle response. Hand starting was a snap.

Some old hands predicted dire consequences would follow. Warnings of "increased gyroscopic precession", stressing the front ball race beyond its rating.

I never noticed any issue. Engine was fine.

Recycled Flyer 12-10-2012 10:27 PM

RE: Tadpoles
 
The issue that I have with adding weight and therefore inertia to the non driven end of any crankshaft is increasing the possibilty of a spiral fracture.

I have seen a few of these in front induction diesel conversions and they radiate from rear corner of the intake cut away in the crank and progress towards the crank web twisting around in a 45 º spiral.

Personally, I think that the weight is being added to the wrong end of the shaft - but if the shaft is strong enough ................

ffkiwi 12-10-2012 10:35 PM

RE: Tadpoles
 
It's a bit difficult adding a flywheel internally.............

CJM

Recycled Flyer 12-10-2012 10:54 PM

RE: Tadpoles
 
Drill out the counter weight and add in tungsten rod seems to be the ultimate.


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