Author Topic: Metric Hoglet - plans ?  (Read 844 times)

Offline GSherwood

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Metric Hoglet - plans ?
« on: February 05, 2022, 03:15:31 PM »
I am looking to build a Hoglet, but being in the UK and with mostly metric gear would prefer to work metric largely for cost reasons.
I see occasional mentions of metric Hoglet builds - anyone know if there are there metric drawings available I could purchase?
Or a list of changes done to make it metric I could follow ?
I have purchased the MEB plans, but at my skill level would rather follow someone's lead rather than try to convert the plans.

Thanks

Offline Jasonb

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Re: Metric Hoglet - plans ?
« Reply #1 on: February 05, 2022, 05:03:51 PM »
When I built mine I only changed the fasteners to metric but if I were doing it now I would go further. It's fairly easy to substitute shaft and hole sizes to the nearest metric, for example the 3/8" crankshaft can be done with 10mm stock, 1/4" pins rounded down to 6mm.

You could go further bringing the bore down to 25mm without too much hard work but if you go as far as using metric MOD gears then some more careful calculations are needed.

Some people simply express the imperial sizes as metric but that won't be much help to use as you want to use existing metric tools and materials and I don't tend to consider that a proper conversion as it's simply working in different units.

I've had a Hoglet Facebook group pop up a few times, may be worth asking there too
https://www.facebook.com/groups/849305792539898

Offline Roger B

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Re: Metric Hoglet - plans ?
« Reply #2 on: February 05, 2022, 05:06:32 PM »
Achim (fumopuc) did a metric version here:

https://www.modelenginemaker.com/index.php/topic,6835.0.html

I expect he will comment later
Best regards

Roger

Offline Jo

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Re: Metric Hoglet - plans ?
« Reply #3 on: February 05, 2022, 05:50:23 PM »
Some people simply express the imperial sizes as metric but that won't be much help to use as you want to use existing metric tools and materials and I don't tend to consider that a proper conversion as it's simply working in different units.

Yes JB is referring to the fact that I convert all of those weird fractional  :headscratch: measurements, or those Imperialistic decimal measurements, into standard engineering dimensions for machining in my workshop. My old ex-industrial machine tools are imperial but they are fitted with DROs so you can just press the inch -> mm button they all work in metric measurements  :whoohoo:


Rule of thumb with model making you make things so that they fit together, so unless you are going into production it matters little what the actual measurement is so long as the machined measurement overall does not have any wider impacts. Unless you are using ground stock, you are going to be machining most if not all surfaces so why start an avalanche by trying to change to "standard" whole measurements and risk messing things up by missing one or getting your maths wrong? When I worked in engineering we worked to appropriate measurements and never tried to constrain ourselves to trying to keep to whole numbers.

Just get your calculator out and convert the legacy measurements into mms, it is easier to leave the gears as 32DP.

Jo

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Offline Jasonb

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Re: Metric Hoglet - plans ?
« Reply #4 on: February 05, 2022, 06:39:50 PM »
Jo, did you miss the point about wanting to use his existing metric tools? There are a few items, the two I mention for example that would be PGMS or silver steel into reamed holes.

As the OP says he already has metric tooling then surely it is better to use stock that fits into a hole formed with a 10mm reamer he  has than buying in a 3/8" one

Or why turn down readily available 5mm nonimal stock to 0.190" to put a #10-24 thread onto it with dies he does not have when using readily available 5mm stock and M5 die that he has will do

As for DRO's bear in mind that many who have to ask about conversion will like the OP have limited experience and quite probably new to the hobby so may not yet have DROs fitted to their machines which may well also be modern metric leadscrew ones so having whole measurements makes it a lot easier when trying to keep track of handwheel turns and compensate for backlash
« Last Edit: February 05, 2022, 07:02:18 PM by Jasonb »

Offline Jo

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Re: Metric Hoglet - plans ?
« Reply #5 on: February 05, 2022, 07:41:20 PM »
Jo, did you miss the point about wanting to use his existing metric tools? There are a few items, the two I mention for example that would be PGMS or silver steel into reamed holes.

As the OP says he already has metric tooling then surely it is better to use stock that fits into a hole formed with a 10mm reamer he  has than buying in a 3/8" one

You are assuming he has a 10mm reamer... it all depends what tools he has, wrt reamers he makes do with what he has or bores/turns it to an appropriate size.

Quote

Or why turn down readily available 5mm nonimal stock to 0.190" to put a #10-24 thread onto it with dies he does not have when using readily available 5mm stock and M5 die that he has will do

5mm is not a standard stock size, 4mm or 6mm is. Metric threading tooling is are easy to come by as is BA, rather than foreign threads which are not as cheap or easy to come by in the UK.

Selecting an appropriate size is just a case of applying a bit of "common sense"  ::)

Jo
« Last Edit: February 06, 2022, 10:34:38 AM by Jo »
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Offline Jasonb

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Re: Metric Hoglet - plans ?
« Reply #6 on: February 05, 2022, 08:00:25 PM »

5mm is not a standard stock size, 4mm or 6mm is. Metric threading tooling is are easy to come by as is BA rather than foreign ones which in the UK you can't get easily.

Really, never had a problem getting most things in 5mm dia and thickness, 4mm choices are more limited. Can't get  flat bar in 4mm. It's all these old imperial sizes that you choose to use  that are becoming harder to get, still no easier if you describe them in metric measure. As you say metric threading tackle is easy to get and probably why the OP has it, so why would he want to get BA that he may not have? , plenty in 5mm.

It's no different from you saying in the Baily thread you will use BA because you have the taps & dies, if the OP has the metric gear then lets help him use it. Unlike you having to then use imperial stock to suite your 2 and 5BA threads he can use readily available 5mm and 3mm stock to suite M5 & M3 dies. Be that Silver steel, PGMS ort stainless which will use the supplied surface sor shafts and rods or BMS for things like studs.

Offline Jasonb

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Re: Metric Hoglet - plans ?
« Reply #7 on: February 05, 2022, 08:17:41 PM »
just seen your edit, so where did you get that 4mm was standard, can't see that on your examples. As for the PGMS it's more a case of 6mm or 1/4" is the smallest they stock. if a ground surface was needed then in either case you would pick 3/16 or 5mm silver steel depending on what system you work to

If you look at the current 2022 catalogue not the old one you have you will see that there is more choice in 5mm as they also do EN1A in leaded unlike the 4mm, and also available in EN3

Offline fumopuc

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Re: Metric Hoglet - plans ?
« Reply #8 on: February 06, 2022, 08:36:02 AM »
Achim (fumopuc) did a metric version here:

https://www.modelenginemaker.com/index.php/topic,6835.0.html

I expect he will comment later


A lot of information already given here.
I can add only, that I have gone the very easy way also.
The imperial gears has been purchased at HPC in the UK if I remember well, so should be possible today also.
Shafts, bearing bushes and bolts has been modified to metric dimensions.
My bore was made to the original design dimensions and the relevant O-Ring, used there as a piston ring, an Amazon buy.
Basic was the plan set of MEB with some hand written notes.
Later, as the engine was nearly finished, when I have started my Fusion360 adventure, I have played around a bit with a CAD model.
But that was not relevant for the build.


 
Kind Regards
Achim