Nalon Viper

Hi John MC

That`s pretty well how all high performance engines are made although the circlip is often replaced by a threaded locking ring.

John Feeney

It's one way of doing it but not would not be my choice. Just make the crankshaft 10 thou longer and then you can clamp up the rear part of the crank against the centre of the front bearing .The the expansion of the front housing is taken up by the crankshaft moving in rear bearing. The front bearing can be held in with a circlip but I have found it uneccesary, I have clamped the front bearing in one engine I modified but used a clamp ring ring with a left hand thread so if the bearing did rotate it tightened up the ring.

The easiest solution is to make the front housing out of steel as is current practice in modern tether car engines press fit bearings C3 or 4 tolerance and the expansion problems almost disappear.

Thanks for your contribution John - your set up is exactly as I described before only reversed. The float of one of the bearings is usually at the front end

I have to say that I have never seen this set up as you have drawn in any small single cylinder engine I have been involved with over many years and never ever have I seen a front (or rear) bearing in one held in with a circlip.

Whilst I accept it is just a sketch it also implies there is a considerable gap between what appears to be a bearing 'spacer' and the crankcase bore. Again I have never seen any engine fitted with such a spacer only the crankshaft acting as 'one piece' This gap (and there should be one for lubrication) should only be in the order of a thou or so otherwise crankcase compression will be lost. This may be okay for spindles etc but it certainly isn't the norm for small IC engines that I have had experience of.

Like all matters there is always several ways to skin a cat but for the type of engines being discussed here this isn't one I would consider as neccessary.

The above not intended to be dismissive of your input which is well meant I'm sure but I don't think this is the right advice for anyone attempting to make one of these small engines

Regards - Tug

Johm Feeny I cannot say I have seen a modern engine like that who made them would like to have a look. My interest is going fast so anything new is of interest.

Have a read of this it's very interesting approach to the problem of bearings in aluminium crankcases. I have built a 10cc tether car engine designed Mats Bohlin using the front end as described in the article it requires great accuracy to make it work.

Its interesting at the time Mats built this engine Picco was also racing, his engine was conventional design pressed in bearings in aluminium crankcase, Picco set the World record for a 10cc tether car at a fraction under 345kph Mats engine was 0.1kph slower.

http://bmpra.bmfa.org/wp-content/uploads/2016/12/FMV-Engine-history.pdf

On the UK Combat fliers FB page there is a modern combat engine ( think 20-23K rpm), probably Ukraine in origin, shown in all its glory and no spacer or circlip, what I would call ordinary design, should expect the Viper to be an order of magnitude less in the RPM range! If mine runs and starts easily will be well chuffed as I'm not a trained toolmaker/engineer and it is a complicated engine compared with what I've made before.

Cheers

Graham W

The definitive source on high performance model engine design is the FMV Story. Although it is 40 years old the principles don't change. They include a detailed description of the main bearing design referencing most of the techniques discussed above.

Roy

http://bmpra.bmfa.org/wp-content/uploads/2016/12/FMV-Engine-history.pdf

Reading all these latest posts, particularly on hi-po engines it comes to mind what sort/class of machinery is being used.......... are they outside the normal 'run of the mill' used by the what I believe is the majority of model makers?

Yes of course Jason, must look more carefully at these details.

Emgee

Graham

My interest is racing tether cars the smaller classes1.5, 2.5 and 3.5cc these rev around 40,000 their life is short.

Most of my work is modifying existing engines, making new pistons out of high silicon content aluminium etc.Crankshafts I have made in Hungary and liners chromed and ground in Russia.

My workdhop is fairly standard model engineers one Myford 254 lathe, Seig X3 milling machine and drilling machine bench grinder plus a tool cutter grinder. The latest addition is a Seig KX1 cnc mill.

Hello John,

I am most interested to see your confirmation of John (MC's) assertion that this is how the make up should be. What area of high performance engine would you be referring too here for though as previously said I have not operated engines at a high end competitive level I would say that I have operated, stripped and rebuilt what would be considered high performance diesel and glow motors over time - SuperTigre, Rossi Ops etc. I have never seen such a set up as described by John in any of these engines so would be very interested to learn more.

Have you set the bearings in your diesel in this fashion as from it's appearance I would guess at a high revving scheurle ported 1.5 with good perforrmance in mind from the outset. You may have missed my previous post but again would like to say you have made a superb job of it and I would certainly like to know more about it.

With regard to Johns drawing the other thing to note is that a flywheel is shown and not a propeller. Obviously a prop would create forward forces that would all be taken on the front bearing as drawn. In a marine situation of course it would be the other way round. How those forces act within a tethered car I have no idea - I assume if a twin shaft engine is used then the forces on each wheel act on the engine laterally pushing on one end and pulling on the other?

I'm afraid I can't quite agree though with Johns assertion that most of these engines bearings are set up incorrectly - yes drawings sometimes do not meet expectation but overal I feel its a bit misleading. That said I'm always willing to learn so all input is always of interest.

Here are my latest engines - 5cc versions of the Mk 3 Oliver Tiger

Hope this will be seen as a post of interest in the subject matter and to further Grahams interest in producing a worthy runner

Regards - Ramon - aka 'Tug'

Edited By JasonB on 19/12/2019 15:48:56

I suppose things may have moved on a bit with time, a high performance engine from the 50s and 60s like Ramon bases his scratch builds on is probably a bit behind current day thinking.

Ramon, your images are not showing on the forum

Edited By JasonB on 19/12/2019 13:26:59

Hello Jason, yes I guess they are but if commercial engines have moved on it would be interesting to hear about them. My last high performance engine was an OPS 90 marine - I didn't strip it down however but would never imagined it had the set up as described above - maybe it did - anyone know? Do these small 'nitro' engines fitted to R/C cars have such a lower end - I'd certainly like to see their make up if so.

Can't explain the image situation Jason I pasted the URL in the box and set the image size - it appears on my PC okay.

The full build and images can of course be seen on MEM here

Regards and Seasons greetings - Ramon

Ramon

The current top performing pylon racing engine used in the FAI Class F3D 6.5cc 2 stroke glow ignition powered models is from MBProfi in Holland, the earlier articles describe his engine development for c/l team race engines.

The crankshaft on these engines is supported at the front by a ceramic ballrace and secured by a locking ring, the bearing is shimmed to achieve the required shaft endfloat.
The rear is supported by ceramic balls running in a groove ground into the shaft and an outer race, the cage is a phenolic material.

The builder is currently experimenting with fit of the rear race and has found less problems are encountered if there is good clearance within the bearing arrangement.

Rob is still making team race engines from solid and competing in most European control line contests, he also flies in F3D class using his own engines.

Emgee

Dismantled engines to give some idea of design,

Edited By Emgee on 19/12/2019 14:31:04

Edited By Emgee on 19/12/2019 14:37:14

Ramon, they are not sowing on MEM either as I looked earlier and would have pasted an image from there.

Well that is something really special Emgee but I'm sure you would consider that it's far from the average home model engine builders scope Ceramic balls running in a ground shaft and steel housing is not going to be carried out on the average Myford I guess. Awesome looking product though what kind of rpm and power output are these engines producing ?

I well remember the original article in Aeromodeller by the Meketmeyer brothers but that was long before I took any interest in making engines myself.

Looks like Jason is right, things have moved on but I still think that what I do and what Graham and any others with similar interest in making a small diesel require is far more basic. As I read it the inference of John MCs initial post was to suggest such is required for the kind of engines like the Nalon Viper. I find myself at odds with that view - I simply can't see the need.

In answer to Grahams question about kit all my engines have been made on a Super 7 and an old Linley mill. All bores are lapped not ground which has proved immensely successful - for what I want of it - but the engines you show there are a completely different level and world away from anywhere I have been or indeed from the Nalon Viper that began this interesting foray into modern engine techniques.

Thanks for sharing the pics and info though - the engineering is indeed very impressive

Tug

Hi Jason - I can see all images posted on MEM on opening however I have just called a friend who tells me all he can see is the no image logo. (On the Oliver thread)

I simply can't explain it - all my images are, and have been for years, stored on Google Photos (previously Picasa) and they are all in order as far as I can see.

I do notice that some folders say shared and others not - I cant find anything so far that lets me 'share' those that aren't but I'm ceratain that this is not something that I have done in the past ie make them 'shared' in order to post.

Any suggestions welcome as whatever it is has ruined an awful lot of posting if it is elsewhere too - can you see anything on the wide a wake thread?

Many thanks - Ramon

It's that same issue you had once before where people just see a no entry sign, Wide Awake is OK. the shared option may be the issue as it is a bit like you have them set to private.

You could always upload a couple of pics to your album here for the purpose of this thread.

Thanks Jason - I'll look into it - back later, hopefully with a couple of pics

Thinking about it a bit more even the Viper design had moved on from earlier engines, just look back at some of the other engines Ron drew up and put into the Motorboy's books - some had the shaft running in nothing more than a hole in the alloy casting and then plenty more with just a plain bronze bush, it is not until the later ones that we start to see ballraces. The Lightweight tether boat engine that I made a few years ago just had plain bearings yet the Stuart literature at the time touted it as "one of the crack engines in speed boat racing" and it probably was back in 1935 and is a world away from the engines that Jim Allen documents on MEM.

As Ramon says a lot of hobbists who want to make a small IC engine are not looking for performance, most would be more than happy to just have an engine that runs at the end of the construction. Yet others build with the aim to get the best possible performance from an engine and are constantly looking for ways to squeeze that last little bit out. An engine like the Viper is ideal for them as it's not too complicated and not requiring castings also makes it attractive to those doing their first engine or two. Maybe some will get the bug and want to start to develope higher performing engines others may not.

I certainly fall into the first group and won't really run an engine after I know it actually works, maybe just the odd run with friends and like minded people and at the odd show, putting any of the engines into an airframe, hull or chassis has no appeal to me personally.. In fact on the recent Midget which was again a tether boat engine I even altered the cams and timing to get a slower revving engine as I wanted a nice sound rather than an all out screamer and for that there is really no point in altering the design from the same plain bronze bearings.

So long as you enjoy your way of doing it that's all that matters.