Is anyone interested in developping a new series of model engines?

[JasonBModerator @jasonb]

I think most people would put up with a few minor cosmetic defects provided the part was usable and only needed a reasonable amount of clean up not completely machining all over. The main issues that are not wanted are unmachinable hard castings, excessive mould shift particularly on smaller castings, undersize castings and blow holes where they are not sorted with a bit of filler such as flywheel rims and cylinder bores.

I think what got me into building from scratch was having to create parts for engines where the castings were pants, that group of small ones was from quite early in my building journey but I actually enjoyed the research as to what the parts should look like, designing them at a scale to suit the engine and then making them.

I’m sure some engines get started and then put under the bench when a builder looses heart due to problems. This engine I’m working on at the moment is 2nd or 3rd hand. Originally I was asked to tidy up the cylinder casting and machine the flywheels as the owner could not fit them on their lathe. You can see in the past someone gas tried to get a few flat surfaces so it could be held in the 4-jaw for boring. There is some quite bad shrinkage particularly on teh top right.

Some might be happy to leave it with the wonky cast surface which was 2.5mm low in places but thats not for me so it was machined all over

The bore still has more pock marks than the earlier mentioned spotty teens, the long 3/16″ for the valve steams have wanderd and the pockets for the valve seats are not concentric to those holes, taper, wrong depth and wrong diameter no matter what depth you measure them at. The 4 holes with counterbores are all off too.

Depending on what that casting might have cost if it is going to need so much work externally then there is a good argument for starting with a solid block. Not only can the exterior be made to look half decent you won’t have voids to spoil the bore of deflect the drill when doing the long deep holes. It will also be cheaper based on todays costs for solid and what I would likely pay for a casting and that does not include pattern work.

You will be pleased to know I have worked my magic on it and did a temporary lash up to check there was life in it.

[paulmichael1084Participant @paulmichael1084gmail-com]

@ja quality is definitley more important than cost. 100%.

I’m not interested in competing in a race to the bottom.

[paulmichael1084]

On paulmichael1084 Said:

I’m not interested in competing in a race to the bottom.

It would be a good idea to research your demographic and market areas (UK only or including EU/US for instance) as a first step. There are MEs who understand quality and are prepared to pay for it. But there is also a (possibly larger) group that will not/cannot pay but still expects quality and service.

Until the above is decided arguments about metric/imperial, castings or not and the content of the kits is not important.

I wish you well in your venture but I don’t think you’re going to get rich doing it.

My only experience of buying a ME kit, for a model hit ‘n’ miss engine, wasn’t a happy one. Relatively expensive and alloy castings not great (I binned quite a few of them). Some materials listed as included weren’t, and when they were supplied they were undersize, as were some of the castings. Drawings were CAD produced, but were incomplete and there were quite a few noddy errors in dimensioning and thread call outs.

The drawings for my current engines are old, incomplete and imperial. I use them as a guide and am redesigning the engines in 3D CAD, in imperial as it happens, but I don’t get hung up on measurement styles as they are just numbers. Quite a lot of material is still available as imperial but sheet and plate has gone fully metric so I take account of what I can get in CAD. Threads are a mix of metric, BSF, UNF and BA. Most of the hex sizes for the nuts (I am making most of the studs, bolts and nuts myself) are metric as I have metric hex collets for my repetition lathe. My centre lathe is imperial, but vertical and horizontal mills are metric and I always program the CNC mill in metric, even for imperial parts.

Julie

[paulmichael1084Participant @paulmichael1084gmail-com]

@julieann Thank you for taking the time to write such a detailed reply.
I don’t plan or expect to get rich from this. My motivation is to remove barriers to entry for people like me and younger, and believe me we do see imperial as a barrier. That may well be a filing on our part, but it is a barrier none the less. Other barriersd include not being able to source in one go. See my example above involving a FAG bearing.

“My only experience of buying a ME kit, for a model hit ‘n’ miss engine, wasn’t a happy one. Relatively expensive and alloy castings not great (I binned quite a few of them). Some materials listed as included weren’t, and when they were supplied they were undersize, as were some of the castings”

These problems are high on my list to solve, and I know I can.

I would rather make a bit less money and be proud of the product I supply, than make myself rich by offering a shoddy product. For anyone looking at saving every possible penny then I suspect my product will not be for them. But then again, “Buy cheap buy twice”.

[paulmichael1084Participant @paulmichael1084gmail-com]

@pete41194 Thanks for your input and the tip on the book. I just ordered a copy and will fully digest it’s contents

[paulmichael1084]

On paulmichael1084 Said:

@ja quality is definitley more important than cost. 100%.

I’m not interested in competing in a race to the bottom.

I do still feel there is a maximum price point someone would spend on a first casting kit, yes there are a few who may pay a premium but you still need to get them to buy your engine over a similar offering from an established supplier

You mentioned my engine with the horizontal flywheel. I would put this somewhere between a Stuart single cylinder oscillator and the Progress oscillator if looking a similar kits.

 

So a reasonable retail price might be £120, the only thing you don’t get with the stuarts is a tin of  paint, otherwise they are quite inclusive. Allowing for a reasonable markup that will put your costs per kit at £60 and give you a similar gross profit.

Out of that will come design costs, making prototypes to prove the castings and design, Web site and web shopping. Someone to make up the kits and cut all the barstock, storage of same, someone to process orders and get them in the post, advertising and promotion which could be giving a set for review.

As the castings are going to make up the largest part of your costs it would be worth getting some CAD designs finalised for the patterns, you can then send the images and weight of the castings to a few foundries and see what it is likely to cost for say 5, 10, 50 & 100. No doubt using match boards would get the casting cost down but you would have to pay someone with casting knowledge to do that as it includes gates & runners not just the basic pattern for the parts.

If the sums add up then you can start pricing the materials, etc and then looking into the overheads to see what you may end up with for your efforts.

You would also need to decide what level of beginner you are aiming at. One who has just got a lathe and wants to start off with a kit. Or more likely someone who has had a lathe and possibly mill for a while, built a couple of simple barstock engines and a few tools and is now looking to try a casting kit, they are likely to need a less inclusive kit than a raw beginner and may not want to pay for things they have already aquired along the way.

[paulmichael1084]

On paulmichael1084 Said:

…we do see imperial as a barrier. That may well be a filing on our part, but it is a barrier none the less.

I am old enough to have been taught imperial measures at primary school. But was thankful at secondary school that for science we used SI units. Slugs anyone! I have no problem with metric, almost all my design and machining for clients was metric, except for the US. That is one reason to think about markets up front, the US will mostly likely expect imperial and unified threads.

Julie

 

[John PParticipant @johnp77052]

Hi

I have tried   to send you a PM  but i does  not seem to recognise   your name

perhaps you would  PM me with your email  address

John

[paulmichael1084Participant @paulmichael1084gmail-com]

To everyone why has taken the time to join this conversation, thank you. Every comment has been interesting to read, and there have been many unseful and insightful comments.

I had already started looking for a foundry and now I have some more informtion for that discussion.

To bring the conversation full circle does anyone have any designs they would like to share, or develop in calaboration?

A final very big thank you to everyone who has contributed.

[duncan webster 1Participant @duncanwebster1]

I know of iron foundries in Wigan http://www.jte-castings.co.uk/ and Altrincham (Whiteheads). I’ve dealt with JTE, lovely castings but quite simple (disc wheels). Never found a brass/bronze foundry in this area, if you find one let us know

[paulmichael1084Participant @paulmichael1084gmail-com]

Thank you very much for that @Duncanwebster1, and they are ideally placed near me. I shall make contact on Monday

Much appreciated

[JasonBModerator @jasonb]

Out of curiosity, I modified the parts from my “Orbital” model and emailed the details to East Coast Castings to get a price for 10 of each – Flywheel, cylinder and base column, the latter two cast as one. They said it would be cheaper if two of each pattern were provided which makes sense as they can all be done in one small box which saves time and if one hole to feed then down then just one filter to pay for.

 

I’ll not post the price here as you will all know how much of a Killing Paul will be making😉 but I have emailed it to him.

I does bring up the question of what sort of beginner the kit should be aimed at. I cut the cylinder from a piece of CI bar, to get the distinctive flutes on teh outside would need some form of dividing and ideally a milling machine or at the very least a half decent vertical slide. The base column was turned from round bar but I did make a form tool for the bead and do some hand held turning both of which may put a beginner off but it would be a new skill to learn.

Going the casting route for those two parts is looking like a mimimum of 15 times more costly than what a suitable bit of barstock would cost.

As for the flywheel in the right hands a rotary table would give you something very close but is it expecting too much for a beginner to cut the spokes that way? both in what tooling they have as well as ability. Similar price difference between a cast flywheel or material to cut one from. In both cases the rim is separate from thick wall tube.

Or does Paul really come upto date and provide materials, drawings and .STP files on a stick. Having seen the results John Hinkley got with his desktop Cavera Air CNC you could soon pay for that out of the money saved on a few sets of castings.🙈🙉🙊

[paulmichael1084Participant @paulmichael1084gmail-com]

Firstly thanks @Jasonb for not giving away the trade secret, but I suspect the cat may be out of the bag when I update my profile picture to my nee McLaren!

Your thoughts and analysis on various manufacturing methods are very useful, and much food for thought, thank you.

I have considered laser cut for the flywheel but worry that it won’t give the effect of cast spokes without much fettling or maching. Thoughts anyone?

[paulmichael1084]

On paulmichael1084 Said:

 

I have considered laser cut for the flywheel but worry that it won’t give the effect of cast spokes without much fettling or maching. Thoughts anyone?

Straight from the laser cutters it won’t give the effect of a casting and will look like someone has just milled it out of a piece of plate. It will help a beginner who can’t machine the triangular cutouts due to no rotary table but they could just drill 3 large and two small holes which many are happy to do with other barstock designs but they look just that -something made from barstock.

With the aid of a rotary table and a round over bit a builder could get it looking a bit less angular. A lot of filing would also give a similar look.

But if a builder is going to do the rounding then they may as well do the holes as well. Might even be easier to start with a square plate so you could have some fixings in the corners to hold the metal to the rotary table . Also easier to supply a piece of square material.

At the end of the day it will come down to what you want to supply and to whom. Is it a beginners first casting kit that is different to the traditional subject matter and a step up from bearstock designs. Or is it going to be just a barstock and hardware kit where you ar ejust saving them the job of sourcing items from various suppliers? The latter can be found on ebay for things like the Elmers designs or the likes of Noggin End who do a few materials kits to go with published designs

[Michael GilliganParticipant @michaelgilligan61133]

Just an idea … probably bonkers !

Could the fancy spokes be produced as a plastic 3D print which the builder then fixes into a hefty steel tube ?

MichaelG.

[paulmichael1084Participant @paulmichael1084gmail-com]

That’s a very interesting idea and one I may well prototype.
What material did you have in mind for the print? A strength polymer, or a metal print? After-all the flywheels don’t spin at a very high rate.

Does anyone have any experiance of doing that?

[paulmichael1084]

On paulmichael1084 Said:

That’s a very interesting idea and one I may well prototype.
What material did you have in mind for the print? A strength polymer, or a metal print? After-all the flywheels don’t spin at a very high rate.

Does anyone have any experiance of doing that?

I was assuming a polymer print … hence my casual use of the word “plastic”

… Sorry, I don’t know enough about available filaments to advise.

MichaelG.

[JasonBModerator @jasonb]

A metal print such as Aluminium would be an option. Not sure if you could get the same price from a UK print house but the likes of Craftcloud are approx 40% of the cost of an iron casting based on having 10 done and they would could be printed to the original spoke thickness. It is something I am likely to do on a forthcoming engine – ali spokes and a steel rim.

You can probably do the “plastic” 3D printing yourself but by way of comparison, the C/F reinforced ones from Craftcloud are about 15% the cost of a casting again based on 10 prints and to original sizes.

Both would have the advantage of being able to include the long drilled passage so one less butt clenching job for the beginner.

EDIT. I just ran 10 of the cylinder/column “castings” through Craftcloud and with a bit of modification to make them print friendly in stainless steel they would again be about 40% the cost of an iron casting. Further playing with the way the parts are arranged may see further reductions.  As with the flywheel the flutes could run in the original direction too as they don’t need to be pulled from the sand.

[paulmichael1084Participant @paulmichael1084gmail-com]

@michaelgilligan61133 You did very clearly say “plastic” I missed that, sorry!

[John HaineParticipant @johnhaine32865]

This is an interesting example of what might be done.

https://stirlingengine.co.uk/products/lt3d-3d-print-stirling-engine-kit

Printed plastic flywheel with bearing balls inserted into the rim.

[paulmichael1084]

On paulmichael1084 Said:

@michaelgilligan61133 You did very clearly say “plastic” I missed that, sorry!

No problem at all

MichaelG.

[paulmichael1084Participant @paulmichael1084gmail-com]

@johnhaine32865 Thanks for sending that.
I’ve just ordered 1, and I am quite  excited to get it.

Will post a few pics when I get it

[duncan webster 1Participant @duncanwebster1]

17d sell 5″ g waggon wheels which are a glass reinforced nylon wheel with a steel tyre. Not suitable for passenger cars, and I don’t know whether you can 3d print glass reinforced nylon

[noel shelleyParticipant @noelshelley55608]

Assuming a lathe is used, a bit of bar say 20mmdia and a piece of thick walled tube, say 80mm x8mm wall. Simple dividing to mark out the 6 spoke holes, drill 6 or 8mm and fit spokes of 6 or 8mm rod. Winson thought that loctite 638 would hold it all together ? If this is to be a low cost kit for the beginner would this be a way to go ? Cheap materials and only basic equipment and a passable end result – even if things went wrong the cost of replacement parts is little. Well that’s the flywheel ! Brass or bronze tube for the cylinder avoids the need for a good bored fit – make the piston to fit. Brass bar/strip for the port face and soft solder. A simple overhung crank. A bit of 20mm square  bar and a piece of 30 or 40mm x3mm strip for the base. Throw in a set of drawings and some fasteners and there’s your kit ! Cost ?   Noel.

[noel shelley]

On noel shelley Said:

Assuming a lathe is used, a bit of bar say 20mmdia and a piece of thick walled tube, say 80mm x8mm wall. Simple dividing to mark out the 6 spoke holes, drill 6 or 8mm and fit spokes of 6 or 8mm rod. Winson thought that loctite 638 would hold it all together ? If this is to be a low cost kit for the beginner would this be a way to go ? Cheap materials and only basic equipment and a passable end result

As a beginner I would want a good looking result, not ‘passable’. A cast flywheel would just look SO much better and at about twenty quid worth every penny.

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