A 5cc Twin Shaft diesel engine

Hello Members

It has been a long time since posting regularly on here about a project - not for any untoward reason but simply that of time - a lot of posting has been done elsewhere, mainly on the Model Engine Maker site, and doing it twice or more as some amazingly seem to be able to do has simply not been an option.

The recent discussion on the Nalon Viper thread however has resurected a fairly long held desire to make a 5cc diesel engine with twin shafts suitable for a tethered car so I thought it was time to make amends!

Whilst reasonable experience has been gained over years with model aircraft engines and to a much lesser with model boats the world of tethered cars - indeed any car modelling - is a totally and utterly alien environment.

Some will be aware that several 5cc versions of smaller commercial model aircraft engines have been scaled and successfully made over the last few years but whilst this will no doubt be similar in vein the specific (if there are any of course) requirements for a twin shaft engine are unknown. Hopefully this thread will entice some comment to ensure the right direction is taken.

The first intention is to build the power plant - if successful then it can be taken further. It has to be said from the outset this will not in any way be a quest for outright power nor highest potential speed. Hopefully it will be seen at all times as a model engineering project that will prove of interest and even more hopefully will encourage others to participate in the thread - all input no matter from what skill level will be very much appreciated and help keep momentum.

So, today a start has begun on drawing an engine based on a previously machined crankcase for a 5cc version of the Nalon Viper and already questions have arisen .

Although a lot of engine 'info' has been collected over years there is virtually none on car engines - about the only thing to hand giving any referrence to design layout being the Oliver Story book by John Goodall.

So first my question is - What kind of wheel spacing at the drive end would be considered for a 5cc diesel powered car of the vintage kind. I am thinking about 120mm or so

Second is Tires - that may be a long way off but knowing the width of average tires would assist greatly in establishing the wheel hub width and subsequently crankshaft length.

Thirdly - does the centrifugal action on the car place differing forces on the crankshaft bearings on either side of the engine and if so how would this usually be dealt with - the engine will be fitted with four ball bearings.

There are lots more (questions) but this should get me past the current small hiatus.

So, that's my intent, once designed I'll get to making it and post pics and cover the build - hope this will be of interest to some of you

Regards - Tug

Edited By Ramon Wilson on 30/12/2019 14:48:59

Well I can't offer up much help as the only 4 wheeled use I have any knowledge of is glow motors in buggies but will enjoy following along.

Will you stay with rear disc induction or have to go for a front induction type through the crankshaft due to the second crankdisc and bearings taking up the space where the Vipers disc was?

Edited By JasonB on 30/12/2019 17:02:54

looks like there may have been a class for you to run it in if you had stayed with the original 2.5cc, see part way down page

Edited By JasonB on 30/12/2019 17:23:15

Hello Jason,

No, but I wondered at first if the disc could be incorporated in front of one web much like the 'Atomatic' had but have gone with what the inside of an Oliver looks like from the couple of images in the book. This is an ordinary rotary shaft intake on one shaft.

Drawings are coming on - basic 2D only I'm afraid but enough for purpose. I've been looking at the MEW Nalon Viper liner drawing and the method of transfer porting this afternoon - I think it may be improved with Oliver layout - the inlet timing has been so, increased to 175 degrees from 136 which I guess begs another question - accepted as ideal for T/R aircraft use but would that be an issue in a car?

I can only go as I see it at the mo

Thanks for the link - it's an awful long way off yet but if a car does materialise from this perhaps they'll let me have a run or two - I don't want to go smaller really, much prefer 5cc

Not all my cars are fast the two in the pictures are ones I run at Great Carlton track, they are a simple flat plate chassis with a tinplate toy car fitted these are probably of Chinese origin.

The engine is 2.5cc diesel of Eastern European origin of modern construction ABC liner piston schnuerle porting ball raced crankshaft of normal aircraft construction.

The wheel hubs have been extended to fit the car body.

This is a 2.5cc diesel again but a Russian copy of an Oliver Tiger twinshaft with a bit of work they go well, this one needed the piston lapping to fit the liner way too tight.

The wheels are much closer together on this car, and the plit collets go straight into the wheel hub, same a model aircraft engine.

A Chinese copy of an Oliver Tiger Twinshaft and a Eureka engine same as the one in the Cobra car.

Old School, is the item in the middle of the Cobra some form of fuel shut off that can be operated by catching the vertical rod?

All of this was a completely unknown world to me until the 'Viper thread.. now I find I'm really looking forward to watching things develop, many thanks all.

Jason

Yes it is a shut off, both cars have them operated by hitting the bristles of a brush.

Oliver

Hello Guys - thanks for the pics Oliver - this is all becoming very attractive!

Have just about finished the GA drawing for the twin shaft version of a Nalon Viper - Viperess? There is still a small amount of finishing off to do before making drawings of the individual parts. Hopefully you can pick the bones out of it tomorrow.

Something I did realise today was that I had previously mistaken, and quoted, the inlet timing as 136 degrees - I was thinking that was a bit conservative and had decided to open it to that used on the Oliver (5s) - 140 degrees but then spotted today I was quoting the Transfer period! The Nalon drawings quote a whopping 190 opening at 35 ABDC so shall keep this first engine as close to the the quoted timing specs as possible and see how it goes.

Had a lengthy coversation today with Hugh Blowers, which answered the questions posed re the 'tracking' and width of tires etc. but many thanks for taking the time to take and post the pics - helpful in seeing layout and make up as well.

I've not made a schneurle ported engine to date, my only experience of them has not been good - the only two I've ran (ran ?) was the first PAW 1.49 version and the later CS-09 in Mini Goodyear racing. The former would flood at the drop of a hat if you got it wrong and prove very difficult to start if so and the second - well I don't actually ever remember getting a 'good' run out of it. I do remember some bloody sore fingers trying to though!

Hopefully have a bit to show of the engine layout tomorrow

Regards - Tug

Edited By Ramon Wilson on 31/12/2019 21:46:09

I will also be following this thread with interest its all new to me. I love the look of the tinplate bodies full of character, great stuff.

Edited By Ron Laden on 01/01/2020 07:28:59

Thanks for taking the time to post Ron and Diogenes - hope this lives up to your expectations.

I'm embarrased to say I made another typo on the timing on the last post - despite checking it and re reading it on posting I did not spot it until after it was possible to edit - whoopsy!

So, to be perfectly clear,the inlet timing on the Olivers was set at 175 beginning at 40 degrees ABDC the Nalon calls for 190 starting at 35 ABDC as said and that is what I've made it.

The GA was finished today

and after some enjoyable effort the first two parts drawings done too so a good start has been made

Unfortunately I'm not able to scan so it's photos only at the moment.

Oliver - One thing I hadn't given much thought to, but what sort of wear shows on the secondary crank driven by the crankpin?

All engines to date have had shafts made from En24T running in hard bronze bushed conrods. On the Super Tigre I did locally H&T the crankpin and the drive pick up on the drum valve. H&T isn't an issue but grinding is unfortunately. I'm considering going the bush route on the driven disc rather than H&T at first. I can always replace that with a hardened bush later. Any thoughts ?

That's it for today - time to chill with a tot a bit later

Tug

PS After 'Viperess'  decided to refer to it as Viper - SS

Nooo- not Super Special - Second Shaft 

Edited By Ramon Wilson on 01/01/2020 18:33:30

Ramon, your images seem to be missing again, just the grey no entry sign in chrome and nothing in other browsers.

May be worth putting them into an album on here with the bonus that they will probably come up larger, or e-mail them to me and I'll get them up on the forum for you.

Hi Jason,

I think it should show now - forgot to make the album shared (though it may take a reboot at this end.

Whatever I've added the two images to a new album on here - can I imbed them from there into the text ? Yeh just seen the button

Hows that?

I'll put any images in this folder from here on.

Thanks for the nod

Edited By Ramon Wilson on 01/01/2020 19:30:03

Showing up fine now

One thing that I noticed on all the cars where the engine is laid down flat is that the fins are still orientated as if the engine were upright in the airflow from an aircraft. I would have thought you would get better cooling if the fins ran in the same direction of travel?

I can understand it where aero engines have been converted as they use the same top end but the purpose made car engines could have had the fins designed to suit the application. Looking a current car and heli engines that are not out in the airflow they try and cram as many fins as possible onto the enlarged heads and even the crankcases.

Ramon, if you have the time to post a couple of square on photos of your drawings I would be interested, probably won't make it but may draw it up in 3D.

Are any of these tethered cars 4WD, not needed I guess but just wondered if it has been done, obviously it would need quite a bit more engineering.

I know nothing about the cars but off the top of my head the engine could be turned through 90 degrees and the output shafts connected to front and rear axle diffs.

Edited By Ron Laden on 02/01/2020 08:17:39

That is something that occurred to me Jason as I was laying this out - all that I can see from the limited info available are standard layout so I'll keep to that at this stage but I do think thats a point worth considering in future design (future?) Perhaps others could comment - Oliver? The fact that these (diesel) engines get very hot in this application was mentioned in talking with Hugh but cooling and specifically fins wasn't.

Something you raised before about a rotor disc? I noticed in the Oliver book a break down of an engine using one. It appears the rotor itself is the actual crank web not a separate part as in the 'Ato' - this was driven by the main shaft. Doesn't give any info nor how successful it was - seeing as most after were straight rotary shaft inlet one can only assume it wasn't a worthwhile enterprise commercially but may have merits from a home built outlook

I'll send you it as a PDF later - would be nice to have the skill to do it in 3D but just don't have the inclination to spend the time learning for such little use it would get. Be nice to see you do it though.

Ron, I have no idea but someone will I'm sure - it's an interesting concept though, whether its potentially viable (from a power absorbing perspective) I wouldn't know

Time to get back on the drawing board

Tug

Edited By Ramon Wilson on 02/01/2020 09:47:27

Tug

Tether cars run for a relatively short periods of time, currently the distance they are timed over is 500 metres plus the time to warm up and get to speed at the end of timed run the cars are shut off.

Most of the twinshaft cars are semi scale single seat racing cars grill in the front and vent out of the cockpit, like the Oliver Tiger two five car in the picture. The car is an aluminium casting which the engine is bolted to this works as a heat sink for additional cooling.

i don't think it is necessary to change the fins on the engines, I have never had a problem with any of my twinshaft powered cars and they run for quite long periods.

I will put the pictures up later got to nip to the dentist.

Pictures as promised