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Model Forum / General / Models / August 2010Tiny diesels question
Hi folks, A bit of a long shot, but does anyone know the smallest practical bore x stroke for a working diesel engine? There are issues with atomising (injecting) diesel into a really small space, let alone getting it to combust... I was just wondering if anyone has any info or has perhaps built a miniature diesel engine in the past? Thanks in advance...!  SignatureRegards, Jim M - - - - - - - - - - - - - - - - - - - - - - - - - - - - - NEW e-mail address: railpics at flywheelnetwork . co . uk > Hi folks, > [quoted text clipped - 7 lines] > > Thanks in advance...! I remember seeing small model Diesel aero-engines of around 1cc displacement, these were, of course, 2 stroke with crankcase compression and run on a paraffin / castor oil / ether mix and use a carburettor. I guess from the phrasing of the question you are talking about 4 stroke direct injected Diesels (by direct I mean either into the main cylinder or into a swirl chamber). Martin Signaturemartin<dot here>whybrow<at here>ntlworld<dot here>com > I remember seeing small model Diesel aero-engines of around 1cc > displacement, these were, of course, 2 stroke with crankcase compression and > run on a paraffin / castor oil / ether mix and use a carburettor. I guess > from the phrasing of the question you are talking about 4 stroke direct > injected Diesels (by direct I mean either into the main cylinder or into a > swirl chamber). Indeed I am talking about multiple-cyclinder 4-stroke with direct cyclinder injection. I imagine it would be a bugger to make HP injectors for anything smaller than 0.75cc...! I should have mentioned that! ^_^ SignatureRegards, Jim M - - - - - - - - - - - - - - - - - - - - - - - - - - - - - NEW e-mail address: railpics at flywheelnetwork . co . uk > Hi folks, > [quoted text clipped - 7 lines] > > Thanks in advance...! The smallest one I know about is the Dux designed and built by Martin Alewijn from Holland. The full plans were published in Strictly IC. Although Strictly IC is no longer published, all back issues are still available. I started to build the Dux, but haven't had time to do much to it recently. If you goto my website www.mymodelengines.co.uk there is a page showing what I've done to the dux far, and on the links page there is links to Strictly IC and Min_Int_Comb_Eng yahoo groups which contains some information. Moray > The smallest one I know about is the Dux designed and built by Martin > Alewijn from Holland. The full plans were published in Strictly IC. Although [quoted text clipped - 3 lines] > I've done to the dux far, and on the links page there is links to Strictly > IC and Min_Int_Comb_Eng yahoo groups which contains some information. Thanks for the info. 9.5cc is bigger than I had anticipated. What is the bore x stroke, about 1" x 0.75" ? SignatureRegards, Jim M - - - - - - - - - - - - - - - - - - - - - - - - - - - - - NEW e-mail address: railpics at flywheelnetwork . co . uk >> The smallest one I know about is the Dux designed and built by Martin >> Alewijn from Holland. The full plans were published in Strictly IC. [quoted text clipped - 12 lines] > 9.5cc is bigger than I had anticipated. What is the bore x stroke, > about 1" x 0.75" ? The bore is 22mm with a stroke of 24mm. The problem with diesel injections engines this small, is the fuel supply. The main problem being getting an injector with a small enough hole. Martin Alewijn solved this by not having any moving parts in the injector. His nozzle was created by having the end consist of two cones that screwed together. A scratch is then made on the inner cone before assembly, which provides a suitable sized orifice to atomize the minute amount of fuel needed for the engine to run. The injection pump is made by reaming a 2mm bore into the steel injection pump body. The piston is made by taking a piece off 2mm silver steel, and slitting the end off, which helps create a better seal for pumping the fuel. moray > The bore is 22mm with a stroke of 24mm. > [quoted text clipped - 8 lines] > pump body. The piston is made by taking a piece off 2mm silver steel, and > slitting the end off, which helps create a better seal for pumping the fuel. That is very ingenius! SignatureRegards, Jim M - - - - - - - - - - - - - - - - - - - - - - - - - - - - - NEW e-mail address: railpics at flywheelnetwork . co . uk > > Hi folks, > > [quoted text clipped - 17 lines] > > Moray I think most of the engines used by model aircraft are technically diesels... SignatureJonathan Barnes's theorem; for every foolproof device there is a fool greater than the proof. To reply remove AT > Hi folks, > [quoted text clipped - 7 lines] > > Thanks in advance...! Look back to last October to the thread entitled "Deltic model". Cliff Coggin Kent UK > Look back to last October to the thread entitled "Deltic model". Okay, will-do. SignatureRegards, Jim M - - - - - - - - - - - - - - - - - - - - - - - - - - - - - NEW e-mail address: railpics at flywheelnetwork . co . uk >> Look back to last October to the thread entitled "Deltic model". Wasn't that actually spark ignition? (Incredible bit of modelling though) > >> Look back to last October to the thread entitled "Deltic model". > > > Wasn't that actually spark ignition? (Incredible bit of modelling though) Indeed it is. I wonder if he's completed the 180,000 sparks/min mechanism he required?! Getting back to the thread though, one cyclinder in that mini-Deltic equates to around 8cc, which is still a bit large for what I'm envisaging (if there is such a word). I know you can build miniscule working steam plants (Tubal Cain springs to mind!), but that's a different principal and I'm beginning to think that the reason no-one has seen *really* small diesel engines is because there aren't any! Ah well, 'twas worth a try. Thanks for your help folks. :¬) SignatureRegards, Jim M - - - - - - - - - - - - - - - - - - - - - - - - - - - - - NEW e-mail address: railpics at flywheelnetwork . co . uk >> >> Look back to last October to the thread entitled "Deltic model". >> > [quoted text clipped - 13 lines] > > Ah well, 'twas worth a try. Thanks for your help folks. :¬) Main reason there isn't any that small is because they quite simply wouldn't run. The smaller you make the cylinder, the harder it becomes to heat the compressed air enough, so that the injected diesel will self ignite. This is all explained in the Dux article in Strictly IC. Even if you don't build an engine, it is still a very good article to read, as it shows how a bit ingenuity can solve problems (such as the injector design). moray > Main reason there isn't any that small is because they quite simply wouldn't > run. [quoted text clipped - 3 lines] > engine, it is still a very good article to read, as it shows how a bit > ingenuity can solve problems (such as the injector design). It does indeed sound a good article and I'll read practically anything involving IC engines anyway! So I'll try to get a copy... Thanks for your help on this, folks. SignatureRegards, Jim M - - - - - - - - - - - - - - - - - - - - - - - - - - - - - NEW e-mail address: railpics at flywheelnetwork . co . uk the smallest compression ignition diesel i have seen is the davies charlton bambi which was .15cc.a friend of mine regularly flies models with a scaled down mills engine which is .25cc Signaturebolmas Although compression ignition engines they're not 'diesels'. A 'diesel' injects the fuel into the hot compressed air in the cylinder to initiate ignition. The miniature compression ignition engines take in the fuel mixed with the air and compress both together to get the ignition. > the smallest compression ignition diesel i have seen is the davies > charlton bambi which was .15cc.a friend of mine regularly flies models [quoted text clipped - 5 lines] > bolmas's Profile: http://www.rcgroups.com/forums/member.php?action=getinfo&userid=29260 > View this thread: http://www.rcgroups.com/forums/showthread.php?threadid=317997 thanks for the correction, so what are they called then -- bolma Not necessarily have to inject into the cylinder you are wrong! >Not necessarily have to inject into the cylinder you are wrong! Well...the injection of fuel into a cylinder that has already compressed (and therefore heated) a volume of air is (as I understand it - please correct me if I am mistaken here) an essential feature of the Diesel patent. The point being that the superior efficiency of a Diesel engine is in part related to the high compression ratios that can be used if you inject the fuel into a compressed volume of hot air. If you mix the fuel/air first & then compress it (as is done in the model compression ignition engines), then you cannot use such high compression ratios without the mixture igniting prematurely & resulting in "knocking" or even worse, misfiring and the engine not running at all. So the model CI engines are not Diesels in that sense, although they are often referred to (incorrectly, it would seem) as Diesels. Its a bit like all vacuum cleaners being known colloquially as Hoovers; clearly, a Dyson is a vacuum cleaner, but it isn't a Hoover (although sometimes, both Hoovers and Dysons are washing machines...). But when all's said & done, Hoover hell cares?? Regards, Tony >>Not necessarily have to inject into the cylinder you are wrong! > [quoted text clipped - 6 lines] > Regards, > Tony On the topic of Dyson's did you see the article in the paper where a chap had sucessfully sued Dyson, because his vacuum cleaner had thrown him down the stairs? Steve What's the difference between a worn-out Dyson and a wife? One whines all the time and is increasingly reluctant to give a good suck, but the other is a vacuum cleaner. > On the topic of Dyson's did you see the article in the paper where a chap > had sucessfully sued Dyson, because his vacuum cleaner had thrown him down > the stairs? >>Not necessarily have to inject into the cylinder you are wrong! >> [quoted text clipped - 12 lines] >So the model CI engines are not Diesels in that sense, although they >are often referred to (incorrectly, it would seem) as Diesels. The very specific difference between the Diesel Cycle and the Otto Cycle is that in the Otto Cycle, ignition occurs at constant volume (all at once), whereas in the Diesel Cycle, ignition occurs at constant pressure. with a Diesel engine, as the output increases, fuel is injected for longer rather than faster. This means that carbureted compression ignition aero engines are, in fact Otto Cycle engines (like wot you sed) Mark Rand RTFM > >>Not necessarily have to inject into the cylinder you are wrong! > >> [quoted text clipped - 24 lines] > Mark Rand > RTFM I do apologise for being a pedant but the reason for my remark was that a considerable number of commercial "Diesel" engines had antechambers into which the fuel was injected prior to it entering the cylinder proper. Indirect injection as opposed to direct injection. Still a true diesel. Up until quite recently most light diesel engines fitted to cars had indirect injection. Now it's the opposite with computer controlled injection from a common high pressure rail. snip > I do apologise for being a pedant but the reason for my remark was that a > considerable number of commercial "Diesel" engines had antechambers into > which the fuel was injected prior to it entering the cylinder proper. Good day, I am not much of an RC modeler but do want to build a smal diesel engine for a moped. The plans on Strictly IC are the only ones have found thusfar. Of those plans "The Dux" would seem to lend itsel to upsizing to 49cc and moped use. My concerns before laying down $40 of my hard earned for the plans, ar whether the moving boucing of a moped would kill this engine and wil much diversion from the plans be necessary to upsize from the 10cc moto in the plans to a 50cc motor for a moped. I understand how to make i bigger and maintain tolerances but I wonder if this will undermine th process of how the engine will operate. Ideas? Thank you to whomever takes the time, PS--I have access to a full machine shop and would rather carve tha cast -- dieselquestio >Good day, I am not much of an RC modeler but do want to build a small >diesel engine for a moped. The plans on Strictly IC are the only ones I [quoted text clipped - 10 lines] >PS--I have access to a full machine shop and would rather carve than >cast. I am not familiar with that specific model engine you quote from SI, although I do know of the publication, but all the model engines I have ever come across that are referred to as 'diesel' are not strictly so. They are compression ignition engines, but are carburated with no injection system and run on a fuel that is a mix of paraffin (kerosene), diethyl ether and castor oil, plus a bit of nitrate to help it go pop. You will not be buying this stuff and a normal petrol station and if you buy it from a model shop it's going to be a damned expensive way to get down to the shops. 'though it would smell nice as you pass the bus queue :-) Making a model engine run on diesel fuel is most unlikely and even at 50cc a pretty long shot. I have no idea where you would get a suitably small injector pump and making one would be an interesing challenge. Rgds Richard --- news://freenews.netfront.net/ - complaints: news@netfront.net --- Thank you for the response. I do not get to the computer often and so my replies may not be timely. You answered my question. Before posting this question I had been researching small diesels and found exactly what you expressed. --It would be a bugger-- My hope was that someone at SI site had already worked out the details but such is not the case. There is a fellow on youtube who built a small two cylinder diesel using modified automoblie injectors, but he is a diesel expert and never uses plans or writes anything down. Thanks again Signaturedieselquestion Hi All, Please I am new to all this so I make my apologies first. The Dux Engine is a true Diesel engine, in that it injects regular pump diesel fuel into the cylinder. I obtained the plans from Strictly I C some while ago, make no mistake this is a prototype test rig. It is totally unsuitable for putting in a Moped in a scaled up form. The drawings are a little incomplete and I do wonder if the engine is running full time on the home made glow plug, there is an enormous amount of wire in this small plug. I have been working away quietly for the past few months designing a 10cc "True Diesel", the injector is not a problem 40 years as a Toolmaker gives me the experience to do this. What is a problem is metering a very small amount of diesel, but thanks to a friend at Woodward Diesels this has now been solved and it is just a matter of making the parts small enough. I hope this will help those on the quest for small True Diesels. Regards Graham. PS Those interested in my Petrol Engine endeavours can see my latest effort in the October issue of "Engineering in Miniature", some time back I wrote an article here on" Cams made easy", this was also published on Ron Chernick's model engine site, sadly to those who know Ron he is not very well. >>Good day, I am not much of an RC modeler but do want to build a small >>diesel engine for a moped. The plans on Strictly IC are the only ones I [quoted text clipped - 22 lines] > >--- news://freenews.netfront.net/ - complaints: news@netfront.net --- >> I know you can build miniscule working steam plants (Tubal Cain springs >> to mind!), but that's a different principal and I'm beginning to think [quoted text clipped - 8 lines] >engine, it is still a very good article to read, as it shows how a bit >ingenuity can solve problems (such as the injector design). Might be a suitable role for machinable ceramics, to reduce cooling. (Though you still have to solve the fuel injection problem) - Brian I had a 0.8cc Frog diesel when I was young in an aircraft. It was an absolute b***h. I wouldn't suggest going below 2cc for reliability > Hi folks, > [quoted text clipped - 7 lines] > > Thanks in advance...! dieselquestion Wrote: > Thank you for the response. I do not get to the computer often and so m > replies may not be timely. [quoted text clipped - 8 lines] > > Thanks again These are as small as it get! http://www.ronald-valentine-engines.com/Home_Page.htm -- coriola |
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