Nalon Viper

[Roy VaughnParticipant @royvaughn26060]

John, you seem to be suggesting that the rear outer race should be free to move in the housing. This is exactly the condition that must be avoided at all costs with this type of motor. As Rob M says in his article, the hammering the rear bearing gets will eventually loosen the outer race if it not securely fitted, friction will build up and performance will be lost. High performance motors which use standard ball races often use a nut to secure the inner to the shaft. The philosophy nowadays is to clamp everything up so it can't move. The expense of shimming is the price to be paid.

Tug, thanks for the tip, plenty of C3s to choose from. As to the spelling of Metkemeijer, I recommend copy-and paste!

[Ramon WilsonParticipant @ramonwilson3]

Roy, as said it was quite a while back so pleased to hear they're still available.

I checked the drawings I have – dated 2007 they are for an MB 7ccc motor for aerobatic use. They are copies of Robs initial pen drawings done on squared paper. The crankshaft bearing set up is as most – 6mm width rear bearing 5mm front both push fitted with no retainer.

I was shown an original MB engine to these drawings at the Nationals – 2014/5 I think – and was sent these copies by Roger Ladds. I was at the time laying out a similar motor hence the interest but with other interests in the way never got round to making it. Unfortunately I don't have a full set – just for the crankcase and cylinder as at the time I was just interested to see how he had created such a lightweight crankcase.

I had a quick check in Gordon Cornells book to see what he says about bearing mounting. The only reference he makes to a 'spacer' is an experiment to enable a bore through the engine to take both bearings (of the same diameter) to ensure concentricity and squareness. He comments that is inadisable due to extra components for no real gain

I'm not able to scan but could take pics if required.

Regards – Tug

[John MCParticipant @johnmc39344]

Posted by Roy Vaughn on 23/12/2019 11:02:23:

John, you seem to be suggesting that the rear outer race should be free to move in the housing. This is exactly the condition that must be avoided at all costs with this type of motor. As Rob M says in his article, the hammering the rear bearing gets will eventually loosen the outer race if it not securely fitted, friction will build up and performance will be lost. High performance motors which use standard ball races often use a nut to secure the inner to the shaft. The philosophy nowadays is to clamp everything up so it can't move. The expense of shimming is the price to be paid.

So, the recommendation is to impose a preload on the bearing to try and stop them moving in the case? Looking at the lengths these guys go to extract the last few watts of power from these engines it seems to me to be counter productive.

Frankly, it looks like some engine designers have gone down a non-productive alley with design. While some of what they do is impressive in terms of power to weight ratio, the designs are not so good. Time for a rethink perhaps.

[Old SchoolParticipant @oldschool]

John MC

The crankshaft and front bearing housing has not really changed from the Nalon Viper. The performance from the engines has significantly improved over the years. In the tether car world the crankcase is still aluminium but the front housings are steel with press fit bearings C3 or 4 clearance with ceramic balls.

Various designings of front housing are in use but they all seem to have a very similar performance. I am looking forward to seeing your engine design anything new is worth a try, I will build your front end and put it one my engines and run it on the test rig to see how it compares to what I am currently using.

[John MCParticipant @johnmc39344]

Old School, as you say, design of the bearing housing doesn't seem to have changed much in a long time. I cannot help but think that some of that is due to a lack of understanding of the principles of rolling element mounting.

I would like to know why wide clearance (hybrid?) bearings are being used?

Please don't call it my design, I claim no originality for the design, its good bearing mounting practice and I've seen it used on several engines.

My current project is using a bearing arrangement copied from an engine that was designed and built some 40+ years ago. If memory serves the aim was to get 1bhp from 5cc's, (may have been 10cc's), I think the aim was achieved. I'm no longer interested in sharing this design. I may incorporate it in to a Nalon Viper in the future as there are some aspects of the engine that seem to be good.

The pleasure I derive from occasionally dipping in to the world of small I/C engines comes from the design, manufacture and getting it to run aspects. My aero modeler friends mount them in aircraft to see if they make the power to fly. My present project is going to be tried in a tether car. The engine is not a high performance job, never the less it will be satisfying to see it do a few laps.

John

[Ramon WilsonParticipant @ramonwilson3]

Graham,

I really don't wish to encroach on on your Nalon thread any further than all of us have so far already but given that this will have some relationship, albeit slight, hope you wont mind too much

'Old School'

I have for quite some time wanted to make a twin shaft (diesel) engine of 5cc capacity. This has always been seen as an 'own thought' engine rather than a scaled up version of any commercial product as most of the previous engines have been. At this stage it would, to be perfectly honest, be more for the pleasure of the 'making of' rather than any real intent to put it to the use it should really get. That said however I would very much want it to work at the very best that it's make up that I could provide could do – it may therefore be worth taking it further forward once built and proved successful.

Is there a class for such an engine? I notice in your album the two cars – the one in the foreground more of interest as it appears to be an Oliver Tiger diesel powered through a gearbox – is there any advantage of this layout over a twin shaft arrangement?

I have two finish machined cases for a 5cc version of said Nalon Viper languishing and awaiting a resurgence of interest. One of these (or both) would be ideal as a basis for this thought.

I wonder, if there is any interest, would it be worth starting a new thread on this subject regarding the build of such an engine with your knowlegeable input on it's layout – your thoughts would be most appreciated.

Regards – Tug

[Graham Williams 11Participant @grahamwilliams11]

Tug. Have been fascinated by the amount of information/comment that has been generated and have no problem that a 'slight' deviation to my post has happened, live and learn I say but one thing I'm in awe of is the amount of skill/knowledge displayed by those using the forum, I'm moving along slowly now as made two off cylinder jackets using 2 different methods so getting there. Also sourced another mini lathe at last so I can get on with the lapping though have to make the laps as yet.

Power to your elbow I say.

Cheers

Graham W

[Old SchoolParticipant @oldschool]

Tug

The car in the foreground is a replica of Ian Moore,s Shadow it is powered by a mk3 Oliver Tiger minus the mounting lugs.

The advantage that the gearbox gives you over a twin shaft engine is that you can run much bigger tyres for example on a twinshaft diesel 58mm diameter and on the shadow 70mm diameter. Gives you more freedom in designing the car and easier push starting of the car.

The only classes that exist at the moment are for the modern cars and they are restricted to a fuel with 80% methanol and 20% castor oil, so no diesels.

All is not lost a track is being built at the BMFA,s Buckminster site, it's being funded by tether car enthusiasts, the outer running track concrete has been poured and the apron and centre will be poured in the new year. SAM 35 has been involved and it is planned that initially old timer cars will be run, diesel, spark and glow engines classes 1.5cc, 2.5cc, 5cc and 10cc.

A new thread might be a good idea.

Oliver

 

Edited By Old School on 29/12/2019 18:57:52

Edited By Old School on 29/12/2019 18:58:49

[Ramon WilsonParticipant @ramonwilson3]

Thanks for your tolerance Graham – good to hear things are moving along in the right direction – as said before you're in good hands with John but if I can be of any secondary help on the lapping just say.

Oliver – a little disappointed to hear that its glows only for 5cc but the vintage side of things sounds potentially attractive – I'll look into it further via SAM (I'm a well lapsed member I'm afraid) – I don't know much about Buckminster save that is more or less the same distance as Barkston which is about as far as I want to travel these days. Definitely 'doable' though.

Interesting to hear about the difference in potential using gears but that really ought to be elsewhere so I guess you are right …

I have examined the two cases this afternoon, I'm sure they will be suitable so  will begin on some drawings tomorrow

A new thread it is then – back soon with lots more questions

Regards – Tug

Edited By Ramon Wilson on 29/12/2019 20:22:10

[Old SchoolParticipant @oldschool]

Tug

A 2.5 cc diesel would not be competitive in today's tether car racing they were capable of around 100 mph the current world record for a modern 2.5cc tether car is around 177 mph. The car and engine were built by by Torbjorn in his workshop at home a very skilled engineer.

Oliver

[Ramon WilsonParticipant @ramonwilson3]

Hello Oliver,

Having watched some video yesteday I can well understand that, simply awesome speeds and rpm and obiously all glow powered. It really is amazing how such engine internals cope with the speed of surface movement and reciprocating forces involved.

At this stage thoughts are very low key in any direction save making an engine – what transpires in the future – well who knows?

I've just fired my old computer up which I use for drawing so back in a day or so for some thoughts on the ideas and no doubt plenty of queries

Tug

[Roy VaughnParticipant @royvaughn26060]

Tug, thanks for the offer of drawings for Rob M's stunt motor but that would be far beyond my capabilities! So far I have managed an ML Midge and an Atom Minor. My plan is to build a standard Nalon Viper next and then an update on its design with more modern porting. I like to fly my motors so something like a C/L Weatherman should do as a testbed.

One new to me feature of the Viper is the broached transfer porting. My impression is that broaches are expensive and fragile. Is it worth a try or might I be better off just filing the ports out?

Looking forward to the tether car thread.

Roy

[JasonBModerator @jasonb]

New Twin shaft 5cc engine thread here

[Ramon WilsonParticipant @ramonwilson3]

Thanks Jason

Roy, Sorry for any confusion – I wasn't intending to offer them but of course would have done so had you required them. I very much doubt I will go that route now even having just started to fly C/L again.

I have literally just come in from the workshop having been looking at the Viper liner layout. I haven't broached any ports as yet the angled porting has so far been done with a tool post milling spindle using FC3 cutters. These sometimes have to be ground well back up the shank to get the depth of cut but so far have done the job very well. I expect I'll be doing this with this new project too.

On the Etas I filed the inner tops square to the bore similar to the originals – I believe they were actually investment cast at the Royal Armament Factory at Enfield

Tug

[Ramon WilsonParticipant @ramonwilson3]

Graham – I don't know if you have cut the exhausts ports on your liner yet but I have just noticed that the section drawing quotes to use a 3/16 sltting saw to do so. I'm certain this is a typo and should read 3/32 – the porting as drawn is such. 3/16 is far too wide even if the top edge is set correct.

Hope you've found this already but if not hope this is not too late

Tug

Just looked at your images – looks like you have. Providing the top edge is in the right place it won't affect the timing but if I'm right will give a massive amount of sub piston induction – you may be able to lengthen the piston skirt some to alleviate this.

I'm just drawing out the liner for mine and spotted this – sorry to bring discord to your build!

Edited By Ramon Wilson on 02/01/2020 09:46:36

[JasonBModerator @jasonb]

Ramon, the drawing I have says use a 3/32" x 1" dia saw and cut until the slot is 3/16" wide on the inside of the liner so all may not be lost.

Though the top heights for the one piece and two piece cylinders are different by 23thou as well as the one piece having a smaller height to the slot?

Edited By JasonB on 02/01/2020 10:19:00

[Graham Williams 11Participant @grahamwilliams11]

Tug, both liners have the ports cut, my drg, as Jason's, shows to use a 1" x3/32" slitting saw plunged to 0.134" deep. Managed to find the right size saw at Castle Hardware? in Sheffield, last one they had and made both liners using that, hope the drg is right or it'll mean starting over.

Cheers

Graham W

[Ramon WilsonParticipant @ramonwilson3]

Ah that's great guys – no problems then Graham – my drawing definitely states use 1" x 3/16 thick slitting saw but shows .0935 port width.

These were the early drawings from the site as soon as they were posted – I guess Ron updated them

Whatever – glad you don't have any problems.

I haven't checked the second one piece cylinder Jason – that would give a differing timing all other things being equal at the case – possibly the thinking behind it.

Tug

[Graham Williams 11Participant @grahamwilliams11]

Just a quick question. Made all the parts for the Nalon (though piston might need a nats nuts more taken off as think it's a bit tight) and have now to finish off the NVA. What's the thoughts on that as per drg with a 0.016 cut across it at an angle with a blunt needle or, as I normally make, a cross drilled 0.040 hole with a tapered needle, any advantage either way?

Cheers

Graham W

[Ramon WilsonParticipant @ramonwilson3]

Hi Graham,

I've not seen the design as drawn, on a spray bar before and don't know the reasoning behind it – my thoughts are as yours – just make it a conventional one with one or two cross holes about 0.8mm dia.

It should be made such that the needle meters the fuel at the seat and not at the outlet point.

If its one cross hole set it such that the hole points down the bore very slightly offset from dead centre, if two then on opposite sides across the venturi – not in line down the bore.

There has been quite a few variations on the basic needle design over the years but I don't feel that theres any real advantage over the conventional tapered needle set up at this kind of level.

Not long now before theres a whiff of diesel in the air eh

My drawings are finished and I now have the material but it will be a few weeks yet before I can make a start

Looking forwards to hearing how yours run

Regards – Tug

Edited By Ramon Wilson on 13/01/2020 09:07:22

[Graham Williams 11Participant @grahamwilliams11]

Hello Tug. Gone the tapered needle route as I'm set up for grinding the taper on 1 /16" silver steel, done a few whilst set up as need a new NVA for an AM25, saves making a jig to make to Nalon drg. Hadn't got a 0.8mm drill left, usually drill at 1mm anyway so waltzed off to the local engineers emporium, no 0.8mm to be had so had to settle for 1/32", must be old stock lol. Start to assemble now and see how it goes.

Looking forward to your build on the tether car engine.

Cheers

Graham W

[Ramon WilsonParticipant @ramonwilson3]

'Waltzed off to local engineers emporium' eh Graham – coo I wish. Time was there was a choice of several – all sadly gone but one and that ain't like it used to be.

Hope your assembly goes well, as said it will be a few weeks before I get going on mine but everythings ready to make a start – 'cept time!

Tug

[Graham Williams 11Participant @grahamwilliams11]

Same here as to engineer merchants Tug, only one left where there used to be 4 and usually it's we don't have it but I can get it in a couple of days. Assembly didn't go well as the rotor and drive peg didn't match. Made the rotor using a template filed up from 3/16" bar marking out the centre to drive peg hole and centre popping for the holes which I thought was cock on. Decided to start again and filed up another template with holes distanced using my DRO on my small mill/drill. When I then mounted the tufnol blank to the template saw then that the holding pin, 2BA, was a really poor fit in the hole (3/16" dia) allowing fhe centre hole to drive hole distance to be off so turned up a complete tight fitting pin in the template. Filed the Tufnol, after turning it to dia and centre hole to drg., and fitted it to the backplate and tried assembly again. You live and learn as this time lined up perfectly and bottom end rotated freely so well chuffed. Decided now that I don't like the fit of the prop driver parts so will re-make them and see how it looks.

Cheers

Graham W

[Ramon WilsonParticipant @ramonwilson3]

Yep, sometimes it has to go wrong to learn from it Graham. I usually put the drive hole in the rotor on the mill and then very slightly elongate it to compensate for any deviation. This is something that has got to be right for the car engine – Hugh suggested just a slot on the driven side but I'd prefer to have it aligning if possible.

You can't be far off a run now – anticipation at this end is steadilly growing

Regards – Tug

[Graham Williams 11Participant @grahamwilliams11]

Well that's a disappointment Tried all day yesterday to see if I could get the engine to fire………. nothing. Took it all apart to check if I'd made something wrong but it checked out. Thought the piston fit was a bit tight though as it loaded up the con-rod close to TDC so made another piston 0.0003 smaller (according to my digital mic) which seemed better to rotate easier. Tried again but still no go even on a prime, zilch!. Think it's time to go see John for him to have a look see, if he can't find the problem will have an expensive paperweight LoL.

Graham W

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