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Mills 75 setting up throttle

Vintage radio assist

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Alan Coppen02/06/2019 10:24:47
2 forum posts

I have recently fitted a throttle to my original Mills .75 which is in a Tomboy. On the test stand after overcoming problems with the needle vibrating loose, I have only managed to achieve good even high revs and then a slightly lower rpm at the other end of the throttle arm travel. My previous experience with throttling engines has been with glo-engines, where on Enya and OS motors I had max revs down to a satisfying low rev burble with a smooth transition. I presume that throttling diesels will not achieve the same results as glo or four stroke engines, but I had hoped for lower revs. I have tried different fuels and it seems better on D2000 than D1000. Should I adjust the mixture on high or low setting to begin with? Any advice will be appreciated.

Thanks

Alan

Tom Sharp 202/06/2019 21:15:22
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3462 forum posts
17 photos

Best way is adjust the compression, forget the throttle.

PatMc02/06/2019 21:31:41
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4191 forum posts
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Posted by Alan Coppen on 02/06/2019 10:24:47:

I have recently fitted a throttle to my original Mills .75 which is in a Tomboy. On the test stand after overcoming problems with the needle vibrating loose, I have only managed to achieve good even high revs and then a slightly lower rpm at the other end of the throttle arm travel. My previous experience with throttling engines has been with glo-engines, where on Enya and OS motors I had max revs down to a satisfying low rev burble with a smooth transition. I presume that throttling diesels will not achieve the same results as glo or four stroke engines, but I had hoped for lower revs. I have tried different fuels and it seems better on D2000 than D1000. Should I adjust the mixture on high or low setting to begin with? Any advice will be appreciated.

Thanks

Alan

Unless it's the very earliest Mills .75 it will have sub-piston induction, this makes any throttling very limited in range. If it is an earlier pre - SPI engine the power output will be so low you might not detect any difference. wink 2

Edited By PatMc on 02/06/2019 21:32:12

Simon Chaddock02/06/2019 21:33:24
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5418 forum posts
2833 photos

Couple exhaust 'blanking' with mixture adjustment.

Unlike a conventional inlet 'throttle'. exhaust blanking means the volume of gas to be compressed remains the same and thus the compression temperature rise so it will still ignite the reduced fuel/air content.

The very high diesel compression ratio will also limit the minimum rpm achievable. Use a heavy prop!

J D 802/06/2019 21:35:01
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1229 forum posts
74 photos

If you want a good throttling diesel fit a PAW.

Lovely as the Mills 75 is, it was not originally designed to be throttled. If all you want is less power for the whole flight do what Tom says.

Turn the engine to TDC and look in the exhaust port and you will see the piston skirt edge appear. Any engine like this will not throttle well.

Engine Doctor03/06/2019 21:14:07
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2271 forum posts
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I have a couple of diesel models a Frog 45 and a  50 inch Auster from a  Ben Buckle kit. Both are powered by Frog 150 engines with no throttle and larger tanks for 8 to 10 min run . Just set engine to the speed you want to fly at and launch . Great fun watching the sterile leccy flyers faces when they see and smell the diesel smiley

Edited By Engine Doctor on 03/06/2019 21:16:34

J D 803/06/2019 22:41:36
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1229 forum posts
74 photos

I am the only one who fly's diesel at our club, for some older members it brings back memory's of their youth.smiley Others don't knowdont know what to make of it.

Peter Miller04/06/2019 08:17:14
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10076 forum posts
1192 photos
10 articles

The only diesels that I have ever seen that throttled well were the Irvine .25 and .40 diesels.

The PAWs were very good too but not as good as the irvines.. I had a 1.49 and a .35.

brokenenglish04/06/2019 10:48:32
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452 forum posts
29 photos

Peter, nowadays there are a lot of diesels that throttle superbly All the current PAW TBR range for example And you missed the best of the lot, The Taplin Twin.

TBH, I don't think the OP is a reasonable question. How many people have ever tried to set up an RC throttle on a Mills 75? We're down to conjecture and random opinions.

As stated above, if throttling is absolutely necessary at that engine size, then a PAW 100 (or 06) is the only reasonable choice.

Solly04/06/2019 15:21:39
239 forum posts
1 photos
Posted by Peter Miller on 04/06/2019 08:17:14:

The only diesels that I have ever seen that throttled well were the Irvine .25 and .40 diesels.

The PAWs were very good too but not as good as the irvines.. I had a 1.49 and a .35.

I had the Irvine 20 and it ran and throttled just as good as a glow version. I also had an ED Racer which came with a plastic backplate and a simple barrel type throttle, this also ran very well. And of course half the fun was operating the engines. I must admit I'm a bit puzzled the way some people recoil in disgust at the thought of getting a bit of oil on their models and their hands. It washes off.

J D 804/06/2019 15:56:36
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1229 forum posts
74 photos

If you own a 42 year old Land Rover and service it yourself like I have been this afternoon you will really know what getting oily is.smiley

Solly04/06/2019 16:08:09
239 forum posts
1 photos

Like it! Now brace yourself for posts advising you to buy an electric vehicle.

Alan Coppen04/06/2019 17:16:03
2 forum posts

Thank you all for the advice, I am going to ditch the throttle on this particular engine . My problem really was run time for radio assist. I will fit a larger tank and play around with prop size and settings. I have previously tried a restrictor, a smaller diam plastic insert in the venturi. It worked fine but the decrease in consumption was marginal. I think the original thimble tank is ok for FF but not for radio assist. I also fly electrick, but as an oldie, much prefer "proper" engines!! Viva the Oily Hand Gang!!!smiley

Cheers

J D 804/06/2019 17:57:08
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1229 forum posts
74 photos

Alan, I have fitted my P 75 with a replacement carb/tank from Steve Webb Models for a RC assist Veron Cardinal. Larger than standard tank and unlike the original which was held in place with bend over tabs [ which snap off ] The replacement is screw on. Cheers, John.

Peter Miller04/06/2019 18:19:49
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10076 forum posts
1192 photos
10 articles
Posted by brokenenglish on 04/06/2019 10:48:32:

Peter, nowadays there are a lot of diesels that throttle superbly All the current PAW TBR range for example And you missed the best of the lot, The Taplin Twin.

TBH, I don't think the OP is a reasonable question. How many people have ever tried to set up an RC throttle on a Mills 75? We're down to conjecture and random opinions.

As stated above, if throttling is absolutely necessary at that engine size, then a PAW 100 (or 06) is the only reasonable choice.

I didn't mntion the Taplin Twin but I did fly with one on a Powerhouse. I used the PAW 35 in that and finally ended up with a Merco 61'

MikeQ08/06/2019 07:41:37
96 forum posts
93 photos

Hi

i bought an 'RC' Indian Mills .75cc and 1.3cc from Engines Unlimited (Bipin) years ago. Both throttle very well for small diesels but as mentioned above, you'll not get the same response as from a glow motor.

Mills 1.3cc is currently in a Veron Deacon RC conversion.

Mills .75cc is in a Rover RC conversion

Both great models for a bit of relaxed flying.

Cheers

Mike

PS I've also got a Mills 3.2cc RC that sounds like a motor bike from the 1940s when it's popping away. Noypt sure if this was some kind of 'Indian Special' but got it from EU also. Throttles great too.

Engine Doctor08/06/2019 10:47:29
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2271 forum posts
25 photos
Posted by Alan Coppen on 04/06/2019 17:16:03:

Thank you all for the advice, I am going to ditch the throttle on this particular engine . My problem really was run time for radio assist. I will fit a larger tank and play around with prop size and settings. I have previously tried a restrictor, a smaller diam plastic insert in the venturi. It worked fine but the decrease in consumption was marginal. I think the original thimble tank is ok for FF but not for radio assist. I also fly electrick, but as an oldie, much prefer "proper" engines!! Viva the Oily Hand Gang!!

Hello Alan. I make tanks for my vintage diesel powered models from tinplate . Any size or shape to fit in any available space . Since most diesel engines are a bit thirsty I make them as big as I can to get a decent flight time .I use old Cellulose cans as a source of tin plate and resin cored solder for assembly . Very simple and satisfying job .

One tip if you go this route. Wash new tanks out thoroughly with cellulose to dissolve any flux before using . This saves annoying blockages as diesel fuel doesn't dissolve flux .

Keep up the oily hand society/hand presence yes

brokenenglish08/06/2019 11:02:06
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452 forum posts
29 photos

One point that needs to be made is that, without throttling, you're simply flying in the traditional climb/glide mode, like the Tomboy competitions.
This is great, but the 2 minutes engine run given by the original integral tank is easily sufficient for good flights, particularly with smallish models.
You don't want a model climbing "briskly" for 5 or 6 minutes. It will be out of sight!

Daithi O Buitigh08/06/2019 11:07:51
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1354 forum posts
49 photos

Of course, being an oldie like myself, you should eschew this 'radio assist' nonsense (it's a bit of inverse snobbery). Back then we called it what it was and still is - single channel radio control cheekywinklaugh

Edited By Daithi O Buitigh on 08/06/2019 11:08:12

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