Nalon Viper

[John MCParticipant @johnmc39344]

What fuel are you using?

John

[Roy VaughnParticipant @royvaughn26060]

Graham, fit of the first piston sounds fine so long as the liner is not too tapered and the contrapiston doesn't leak. Check the fuel and that you have the compression up high enough. I'm intrigued as to why you made a new piston when you could have simply lapped the original a bit.

Roy

[JasonBModerator @jasonb]

As John MC has hinted they do nor run on diesel that you get at the petrol station

[John MCParticipant @johnmc39344]

Posted by JasonB on 24/01/2020 13:04:59:

As John MC has hinted they do nor run on diesel that you get at the petrol station

I do hope the OP is not thinking I'm suggesting that he is using pump diesel!

The reason I ask is that I'm wondering what the preferred fuel is, its been a while since I bought any. What with the demise of my local model shop, I'm not sure what to buy. to get my latest engine running.

John

[Graham Williams 11Participant @grahamwilliams11]

OK Guys, fuel is 2 maybe 3 year old D2000, again, Missuses car don't run on diesel from the filling station either as she's now found out coz the new one is petrol powered!!! !have got my suspicions about the fuel, nearest supplier of the good???? new stuff is a distance away but do also have the offer of trying some home brew.

Had made another piston to fit the first liner I made out of EN3, consensus was EN1A was better so made one out of that and that's the one in the engine. Depends on feel I know but first piston miked up at 0.56625 and the second (tight) one 0.56655.The lap I made to do the liner had 0.001 taper as near as I can currently measure. Contra-piston was lapped and is a good fit with no perceptible leak round it. In the past how I've tried to set compression is to advance it and rotate engine until contact can be felt near TDC with piston and then back off 1 turn and start from there.

Think I'll rebuild the Velo gearbox for some light relief.

Graham W

[Ramon WilsonParticipant @ramonwilson3]

Hello Graham, just read of your disappointment but don't despair just yet.

First off you say your fuel is a couple of years or more old – that shouldn't be a problem but… if the cap wasn't on really tight the ether content can gradually evaporate away – seen that happen more than once which usually leads to blaming everything bar the fuel. Do you have another engine that you know runs you can test it with? That said John will have some fresh stuff for sure.

Your piston fit 'sounds' okay to me from your description – a good test if you are not too sure is to prime the exhaust with some neat paraffin and just slowly turn the piston up the bore against compression – you should get a degree of bubbling around the exhaust ports but not too excessive – try again with some fuel – if it is excessive then your piston/liner fit may need addressing.

If the compression feels okay it's got to be something really out of kilter not to at least get a fire from a prime unless of course you have it well and truly flooded. In that case if it feels 'wet' close the needle completely, keep flicking and blowing across the exhaust ports until it seems 'dry'. From this point gently adjust the comp on exhaust primes alone until you get a burst. That should happen 'all things being equal' on the build quality. Once you get a couple of bursts from an exhaust prime gradually open the needle a bit at a time until the bursts start to lengthen hopefully finally into a run.

If you can't get it to fire at all then it's rethink time I guess but if anyone can get it to work it'll be Johnny Alcock

Don't give in quite yet

Regards – Tug

[Graham Williams 11Participant @grahamwilliams11]

Hello Tug. Did as you suggested and tried an old AM25 with a port prime and it fired up no probs so fuel looks OK. Tried the Nalon again as you suggested and finally got it to fire on a port prime but noticed that fuel or gas? was blowing out the Venturi. So took it apart once again and I think I may have misread the drgs as to rotor layout, ie centre pin and rotor drive hole are on the wrong side, nothing to lose so out comes the Tufnol for another try. John is going to run his eye over it and a Mills that always runs backwards next week so hopefully it'll be fixed. Thanks again for your continued input.

Cheers

Graham W

[Ramon WilsonParticipant @ramonwilson3]

Good news Graham – if it will fire on a prime then it should run providing all the parameters are right – that includes the rotor of course .

You won't be the first to make that mistake though and you'll soon have another done.

I had a real issue with one of my Etas at an Old Warden do – it had performed well before but it simply would not run other than firing on a prime and immediately stopping. The symptoms were of flooding but strangely there didn't appear to be an excess of fuel in the cylinder. Finally gave up, concluding something was wrong inside rather than the engine itself, and left it till I got home. Turned out I had been rather over enthusiastic with the after run oil when putting it away previously – taking the backplate off revealed the case was virtually full of oil – soon as it had fired it had stopped itself. Poured the oil out and it was away with no problems.

Another flooding issue was on the second Hunter – I had only run one of them previously – opened the needle the usual amount, exhaust prime and a couple of chokes and immediately went into a flooded situation. Did as I recommended to you – closed the needle off and kept flicking till it fired – it then broke into a lovely consistent run with the needle fully closed! I hadn't seated the needle all the way home when soldering it to the thimble so open 2 1/2 turns was more like 5!

All the fun of making these fascinating little engines – getting a sore set of fingers that is

Keep on trying – Tug

[Graham Williams 11Participant @grahamwilliams11]

Well after 2 new rotors, 2 new rotor pins, 2 liners, 2 cylinder jackets, 2 pistons and 2 prop driver+ collets it runs. Needle is right out so think I need to open out the holes a tad, It's loud, don't know the revs but spinning well on a 9×4.

Tug. When I assembled it initially used liberal amounts of after run oil and am wondering if that was the problem you indicated with your ETA. Thanks for all your input Guys and the merry quips.

Cheers

Graham W

[Ramon WilsonParticipant @ramonwilson3]

Well done Graham – knew you'd get there in the end, I bet that brought a big grin to your face well worth the persistence eh?

If the needle is right out sounds like you may be metering at the cross hole – possibly the jet hole is a little deep past the cross hole in the spray bar, a finer taper might help or make a new spray bar with the jet hole a mil or so deeper than the cross hole.

Sounds like you have near enough for a second engine too. Any thoughts on another (different) engine or is it time to rebuild those AM's etc

Great result mate – congratulations all round on a super effort

 

Regards – Tug

 

Edited By Ramon Wilson on 26/01/2020 13:44:38

[Graham Williams 11Participant @grahamwilliams11]

Thanks Tug, am well chuffed .Will check the relative positions of the jet and cross holes, needle is at 7 deg. taper which is what I've used since reading an article about Gordon Burford, cross holes are smaller than I've made in the past which have been 1mm so thought it may have been that. As to what to do next, will have to be the AM25s, simple engines but I like them. Was also thinking of a FRV such as the Holly Buddy which I have the plans for and even modding the Nalon design with a longer crankshaft and front housing so I can use a sealed (1side) front bearing, sealed ones only available 1/32" wider than original spec.

Looking forward to your tether engine build, hope the plans are coming together well.

Regards

Graham W

[John MCParticipant @johnmc39344]

Great to see the engine running Graham. I'm presently building two engines, close to completion now. One of them has had two pistons already, I use an external hone to finish a piston and neglected to true the hone before sizing the piston!

[Old SchoolParticipant @oldschool]

It's great when they run for the time, well done. Now onto the next one.

[Graham Williams 11Participant @grahamwilliams11]

John MC. What engines are you making, are they Nalons? if yes MK1 or 2 or something completely different? Been shown a different method to lap how I did my pistons using a hand held external lap with piston mounted in the lathe on a jig for want of another term, the method is more like a split collet held in a 3 jaw chuck of a Hobbymat and adjusted by closing the jaws , piston is held on an old conrod and entered into the collet, engineer who uses this method has done many many performance engines and has a wealth of knowledge so will try this next time around

[John MCParticipant @johnmc39344]

I hone both cylinder and piston using Delapena equipment, one photo show a small cylinder being honed while the other two photos show the external honing equipment, one is with the hone on a truing mandrel. To fit a piston (and contra piston) I turn a length of suitable bar to ~0,002" then hone to size, I make the contra piston quite tight compared with the piston. I've "rebored" many more cylinders for others than I've finished cylinders for myself!

Earlier on in this thread I commented the mounting of the crankshaft bearings being poor so I thought I would have a go at doing the job properly with the Nalon Viper, I've modified the "cooling system as well, the cylinder in the photo is for the Viper. Thats one of the engines I'm building, the other is another diesel of my own design, more or less, again with rolling element crankshaft bearing but with a different arrangement from what I have seen in many years.

John

[Graham Williams 11Participant @grahamwilliams11]

Hello John, was turned away from going the speedhone route as I was informed that it was impossible to get the required 'pinch' near TDC in the liner using one, do you not bother with trying to get that slight taper or is there a way of doing it using a Delapena type? I have something similar to your second photo, built from a kit supplied by a company near Long Eaton whose name eludes me but it doesn't go down small enough to do these small pistons. Up to now have made a circular hand held external hone to a design I found on the web for each piston which is time consuming, using an Alum split collet type would appear to be much quicker and so bought a mini lathe to do all the lapping on

More pictures would be good.

Cheers

Graham W

[Ramon WilsonParticipant @ramonwilson3]

Hello John, Graham,

It looks like I may have the same bench mounted Delapena as you have John. Thing is I have never used it. I bought it off Polly Models at an exhibition quite some time ago. It was quite grotty with a damaged pulley and though near done I'm afraid it's still in a state of rebuild. I have managed to get some tooling for it but I have to say that because lapping has proved successful I've never really been motivated enough to finish it. Like wise the external hones. I was lucky enough to get two brand new sets off Ebay and though have used them still prefer to lap pistons with a home made lap

As you can see these are quickly made and do work very efficiently.

Achieving a tapered bore as Graham asks is quite easily achieved by lapping simply by dwelling at the bottom end of the liner – is this possible when honing on such a hone?

Good to hear you are making a Nalon – I look forwards to seeing your method on the bearing set up. Whilst I disagreed with your suggestion earlier it did cause me to look into bearing set up further and can see your argument from a preloaded perspective. It doesn't change my thoughts on all that has been seen before but has given rise to rethinking how preloading could be achieved without a spacer.

Graham – all the drawings are done and material now in hand.

I have another modelling project I need to finish first but hope to be starting this beginning March at latest.

Regards – Tug

[Graham Williams 11Participant @grahamwilliams11]

This is the cylinder lap that I used as recommended by John A, Piston lap is similar to that I used Tug but will try John's suggested method with an AM25 piston this time around. Needle valve jet hole was to deep, almost 0.090 past cross holes so will make another one tomorrow.. Wish my drgs looked that good Tug, foolscap and sometimes a ruler is the best I can do LoL

Cheers

Graham W

[John MCParticipant @johnmc39344]

Graham, never bothered with a tapered bore, I've always taken great care to get the bore (and piston) parallel in these small sizes. I think that the amount of taper required in these small cylinders with piston and cylinder made from the same (or very similar) metal is so small that it would be difficult to measure and I don't like the idea of guessing! I've always tried to arrange effective cooling of the cylinder to try and keep it parallel and round. Screwed on or "slip fit" fins doesn't do that.

Tug, I don't understand your point about preloading. Preloading of the bearings is to be avoided in this type of use, your design will, most definitely, preload the bearings when the engine warms up, assuming they are not when cold.

John

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