sw74gls

Hi Guys I have been offered one of these Aurora k mills 1.3 for a £95.00 but have only limited knowledge on Diesel Engines being a newbie only a few years ago, my question please is this the original k mills or a copy?? Really appreciate your help on this, many thanks Simon.

qazimoto

My Feedback: (1)

The Aurora K Mills 1.3 is an Indian made copy of the original British made Mills 1.3cc diesel. Quality was variable, although some are happy with the engine. GBP 95 is way too much for one. You should be able to get an original or even better an Irvine version for just a bit more. I have an original and an Irvine and the latter is certainly better made.

qazimoto

My Feedback: (1)

Adrian Duncan and the late David Owen have published a comprehensive article on the Mills Replica story. Mostly about the Mills 75, but there's a bit on the 1.3cc as well.

AdriansModelAeroEngines.com :: Mills replicas

ffkiwi

The Aurora is the K Mills-the K stood for Kumar-surname of the Indian businessman who first bought the tooling from the original UK manufacturers...the company which produced them was IIRC the Aurora Model Manufacturing Co located in Calcutta-the original company also produced several other UK designs either as direct copies or as the basis for a modified engine design.

Way overpriced at 95 pound if its a second hand example-a good original might sell for this much-even a new Aurora would have retailed for less,An Irvine 1.3 probably commands the highest resale price-based both on scarcity (they weren't around for that long) and the quality of manufacture. The trouble with the Aurora one is that the quality varied considerably over the years-not just the machining standards-but also the material specs-some had crankshafts that were as brittle as carrots.....though the problem was more pronounced with the 75 Auroras. A good Aurora is quite acceptable-but you can never tell whether it is good or bad without test running and checking it-making the purchase of one a bit of a lottery.

If you specifically want a Mills 1.3 you'd be best advised getting hold of an original or Irvine-though note that spares for the latter have largely dried up-and parts are not generally interchangeable with the original UK ones-though the Aurora and original UK ones are largely interchangeable in parts-though there are a few pitfalls-such as fitting an aurora shaft to an original will require the Aurora prop driver to be used as well, due to the different PD mounting-even though the shaft may have the same journal diameter and length as the original British one.

ChrisM
'ffkiwi'

sw74gls

Hi guys once again thank you for all your help and advice, I am trying to source an original mills 1.3 or/and a Irvine mills and dave Boddington mills if anyone has one they would sell????
also another mills has been offered to me obviously a replica this one is in a blue box with red writing which says k-diesel mills 1.3 and a shop label saying spore hobby? I take it its still a aurora mills replica but of a certain time period? Many thanks in advance Simon.

ffkiwi

Yes correct-this is a Kumar (Aurora) Mills-if it has a plain alloy case it is an early-ish example, if painted black then a later one. Original Mills 1.3s crop up on Ebay fairly frequently-the Irvine ones less so-so keep an eye out there. Note what I said in my earlier post-not all K Mills are rubbish-some are quite good and perform adequately. If the vendor is prepared to run it and show you-then it may be worth purchasing. But an unrun NIB one? Well it might be good, it might be poor-you wouldn't know till you tried running it. Also bear in mind that most UK Mills originals that come up for sale have seen quite a lot of use-so again I would personally ask to see it running before purchase if that is feasible.

ChrisM
'ffkiwi'

WeeTed

Have you any information on the Aurora Indian mills 1.5cc version? Did it have a gold anodised head? Do they have a better hp than the 1.3cc version?
thanks

ffkiwi

Yes to both questions. They are not especially common compared to the normal sized versions, but offer a slight power increase-likewise the 1cc version of the 75. Given that they are only 15% larger in displacement-(in the case of the 1.5 version)-you're not going to see much of an increase-and I would not be surprised if the generally variation in output you get with small engines would potentially obscure it-ie a 'good' 1.3 might well outperform an 'average' 1.5 variant...but the converse also applies...whereas I would expect to see a greater difference in output between a '75' and the 1cc version of the 75. The same arguments about variability however still apply.

ChrisM
'ffkiwi'

WeeTed

Thanks for this explanation. I am building a "Tomboy Senior" 48" and the plans call for a 1.3 Mills. From what I read it might be a bit under-powered using an early Mills (I have just picked up a Mark 1 series 2 )and whilst a good series II would be better, I thought a 1.5 might be the answer.
There is an Irvine Mills 1.3 on eBay and that might be an answer (but its very expensive). I could just use a PAW 1.5 but was trying to keep it as "vintage" as I could.
Any advice?

ffkiwi

Build the back end light-as light as you dare....the Tomboy has a very short nose-and even more so when enlarged from the original size since the tail moment works to your detriment with any enlargement....ie a gram heavy on the tail might take 10g in the nose to compensate. Anecdotal evidence on other fora indicates a tendency to tail heaviness in the Senior variant unless very careful weight control is used during building. Result a lot of lead in the nose and a sluggish model.... This is one case (the other being the very popular 'Simplex) where a heavy engine is a godsend....though the Mills 1.3 and the TB Snr seem like a perfect combination for relaxed flying. My experience of 1.3s (and I have quite a few of them) is the MkIIs run very well on a Topflite 10x3-1/2 nylon-though for max power you want a 9x4... On the 10x3-1/2 they're well below the BHP peak-but sound very happy and run very sweetly-and of course you move quite a bit more air with the 10" diameter compared to the 9" one....for identical reasons I prefer an 8x4 on the 75 rather than a 7x4

ChrisM
'ffkiwi'

PS Give some thought to what you're going to use for control linkages....since weight is an issue down the back, you can't get any lighter than a push-pull cable setup....though its a bit more work installing and tensioning.

WeeTed

Thank you for this insight Chris. I understand the concern regarding the Tomboy being tail heavy. I watched the Mark Robinson videos and he used carbon fibre control rods on his version to keep the tail weight down. Please can you shed some light on the engine choice? I could try to find an Irvine Mills 1.3 and use a big prop like the 10 x 3-1/2 or a 9 x 4. or for a bit less buy a new PAW double ball race R/C and have throttle control. The Mills would keep it vintage which is what i wanted to do, but if it is not able to power it then a more powerful engine is needed. That was why I was considering the Aurora Indian Mills 1.5. I tend to agree with you that a 15% increase of "not a lot" will be pointless, especially if a decent Irvine 1.3 might be as good.

ffkiwi

There is no right or wrong answer here-the TB Snr is a reasonably popular and proven design and it is known to fly more than adequately on a Mills 1.3...in fact Boddo specifically scaled the original to a size he considered appropriate to the power of the 1.3. ...that being said the original designer has no control over how other builders build it and their choice of wood, covering and fittings....bad choices or inexperience there...lead to poor outcomes-ie tail heavy as built-requiring a lot of lead to get the CG correct. A Mills will give relaxed flying, a PAW 149 far more power...on much smaller props-but the advantage of throttling-though with a bit of effort you can find throttles for Mills 1.3s....either original or aftermarket units-I have both types on some of mine. If you plan on other models -especially non vintage sport types-then the PAW 149 might be a little more useful than the 1.3. A lot would depend on the quality of the Indian 1.5-the 75s and 1.3s are known to be quite variable in fits and machining-though I would expect the 1.5 and 1cc versions-which came along towards the end of production-to be a bit more consistent between examples. But I would certainly take an Irvine over an Indian any day. The PAW of course you have the advantage of being UK produced and well supported by the manufacturer, whereas the Indian offerings are out of production now.

CF pushrods as used by Mark Robinson are fine-and less fiddly than pull pull cables-though the latter probably have a slight edge when it comes to the weight of the control system...I know Boddo liked them and used the setup quite a lot on some of his later designs-especially for rudder control.

....I've just pulled out an 'Old School Model Aeroplane Factory' short kit of the Tomboy 48.....which AFAIK is the same ass the Tomboy Senior....looking at the plan in detail with a critical eye I can only reiterate my earlier advice to build the back end light-that means the fin and rudder, tailplane and elevator and any sheet parts like the subfin and sheet infill areas-choose good light wood.....and go for a light covering as well...depending on preference...tissue, silk or a lightweight iron on like Oracover light. At the end of the day I'd still go for a Mills up front...purely because it looks right, if nothing else.

ChrisM
'ffkiwi'

WeeTed

Thanks again Chris, wise words! I shall most likely go for the Irvine Mills. As they are hard to find on the web, do you have any idea on what I should pay for a decent one?

ffkiwi

Irvine 1.3's?...They tend to be pricey-you probably have a better chance of picking up an original on Ebay-where they appear reasonably frequently-as do Indian ones....use that, in the model, and keep a weather eye out for an Irvine popping up somewhere by chance (most are in collections....!)-they weren't made for that long and in my opinion way overpriced when new-about 90 pounds-when you could buy an Irvine 40 for about 50 pounds at the time. A classic case of killing the goose that laid the golden egg-had the price been more reasonable, they would have sold a lot more.

ChrisM

WeeTed

Hi Chris, I picked up a nice Irvine Mills 1.3. It was pretty expensive, but when compared to a brand new PAW or a Redfin 125 it was about equal. It was one from a collection (Jack Law) so does not look like its seen much use. So I shall use it and keep things light on the build.

I have another question.....all my old RC equipment is outdated and having dusted it off I have decided to replace it with something more modern. I really only need three channels and a way of having a "dual throw" rudder (i.e more rudder throw when engine has stopped). Should I just look for an older Futaba T6EX on ebay or should I get something new from Spektrum, flysky or radiolink?

ffkiwi

Look after the Irvine -take care with the running in phase- and you should have no issues with a long and useful engine life. As for the R/C gear-its probably best to go for new-depending on how old the unit is-but all you need is dual rates on your rudder...which is usually an option on all but the lowest specced gear. A 6EX -assuming it is 2.4-should be more than adequate for the type of flying you'd be doing with the Tomboy Sr. I'm not a Futaba user, so not familiar with the T6EX-but if the unit is 2.4 GHz (and not on one of the earlier R/C MHz bands) then you should have no trouble with it-though with a second hand unit you should probably get it checked over by a competent service agent. I'd ask around locally-there's a degree of merit in having similar gear-or the same-as the the majority of your local fliers-that way if there are any issues, someone else may know or have experienced them. If most of the locals use Spektrum, or FrSky, or Futaba, JR or whatever then it doesn't make a lot of sense-other than expressing your own individuality-in buying another brand just to be different....

ChrisM
'ffkiwi'