Member postings for Roger B

This is the vertical slide setup I used on my minilathe. I think that the vertical slide was a Machine Mart one and I drilled and tapped the cross slide to fit it. The first picture is milling a cavity in an oil reservoir. The second one is the set up I used for milling camshafts. The depth for each cut is set using the DTI and the G cramp keeps everything a bit more rigid.

Both the fixed steadies seem to be Cast Iron. I think that the Minilathe one could be modified but for my purposes a bore of less than 50mm would not work.

As you can tell by the discolouration I make quite a lot of use of the fixed steady very little of the travelling steady.

Unfortunately the same applies to music reproduction systems (gramophones). Some people listen to the music, others listen to the equipment. Both are valid hobbies.

You probably have as much equipment as the designer had. Give it a go, there will be plenty of help available on here if you are not sure of some operations.

The possible issue with castings is that replacements can be expensive if you make a bad mistake. With a bar stock engine you just cut off another piece and start again. Most of the loss is just your time.

I have found the box with the lathe accessories in so here are a couple of pictures of the Hobbymat fixed steady compared to a Minilathe fixed steady.

The Minilathe steady won't accept a 50mm bar whereas 60mm fits easily in the Hobbymat one.

Finally a picture of the Hobbymat fixed and travelling steadies. There are tapped holes in the carriage for the travelling steady.

Teco were somewhat slow to respond but delivered what I expected to receive. I bought directly from Teco as it didn't make sense to ship the milling head to England and then back to Switzerland. They were also as expected cheaper.

The Teco head is ike the later Prazi ones with belt drive and MT2. The earlier ones had a geared drive and MT1.

Teco don't offer the option of a combined lathe and mill only the two separate machines so they don't have the adaptor block that bolts to the back of the lathe.

The T slotted table is only fitted for milling. I the picture above it is just resting on the cross slide (the picture was taken to explain to Teco what I had and what parts of the milling head I needed to order).

As far as I can see my toolpost is identical. I works without any problems and allows easy adjustment of centre height. I tend to use it when boring or screw cutting with HSS tools. The tool holders are rigid when clamped but do not always go back in exactly the same place when removed (the larger more expensive versions are more reproducable).

The benefit of indexable tools is that by design the tool tip is the stated dimension above the bottom of the tool. If I put a 10mm tool holder in the standard toolpost it will be on centre. The tips are not cheap and when they get blunt or chipped you just throw them away. I have a selection of 6mm, 8mm and 10mm tools. The smaller ones are set to height with 2mm thick packing pieces. I started out with a Proxxon set

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I have additional holders from Glanze (Chronos) and CTC.

The additional hole in the top slide is to allow the yellow vice to be fitted in milling mode.

The quick change toolholder was comercial item. I also have one and find it useful for setting the tool to centre height for non indexable tip tools.

I have not had to dismantle mine so I can't help there. I don't have a tommy bar, I just use a convenient sized allen key.

Most of the time I use the original tool post with indexable tip tools so the certre height is automatically correct. I believe that the cutaway parts of the fixing bolts are to limit the forca that can be applied to the rather thin top slide.

I think that this key should fit your lathe chucks:

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I guess you already know of RC.

A Hobbymat milling table does exist and appears sometimes on Ebay. The one in my picture is a Unimat one in which I drilled new fixing holes to match the Hobbymat cross slide.

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I like you have very limited space for a workshop and have the milling head on my MD65. This was purchased new from TECO, my secondhand lathe already had the adaptor block.

It is not as rigid as a dedicated milling machine however I have made several working IC engines with it.

I believe that this is a Prazi fixed steady. Not the best of pictures but the real thing is inaccessable at the moment due to a workshop move.

Some thoughts:

The lathe is still in production in the Czech Republic and Pro Machine Tools are the UK agents;

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They may be able to help with change wheels.

If you can manage German this company also claims to offer spare parts;

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I bought my milling head directly from Teco a few years ago I have not used the other two suppliers.

The normal milling set up is to remove the topslide, fix the angle plate to the crossslide, fix the topslide to the angle plate and then fix the vice to the topslide.

The plate is usually used with the milling head that bolts to the back of the lathe base (I believe that the original was aluminium)

The RCexl screened cable and plug cap are probably necessary if you are flying the engine in an RC aircraft but as you say otherwise somewhat bulky.

Best regards

Roger

The RCexl systems will work but the sensor needs to be on the crankshaft, not on the camshaft, as these are designed for 2 stoke engines. The wasted spark on the other TDC is not a problem as there is no combusible mixture.

They start with full advance, 28°, which drops to 4° at around 400rpm and then starts rising at 1000rpm reaching full advance again at 4000rpm. This should be ok for a Lynx but is not suitable for low speed hit and miss type engines.

1/4-32 versions are available from Just Engines and I assume other suppliers.

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Best regards

Roger

They are still available, but not cheap.

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Best regards

Roger

The Dutch engine builder Jan Ridders has produced several designs with glass cylinders and graphite pistons. This is a flame licker:

https://www.vth.de/maschinen-im-modellbau/unsere-beitraege/flammenfresser-mit-glaszylinder-mit-bauplan

And this is a 4 stroke spark ignition version ( the article did carry a warning to run it behind a protective shield):

https://www.vth.de/maschinen-im-modellbau/unsere-beitraege/viertaktmotor-mit-zylinder-aus-glas-mit-bauplan

Best regards

Roger

A couple of thoughts:

Why silver steel for the piston? It tends to rust quite easily unless you have dry air and good lubrication this may be a problem. Precision ground stainless steel is available.

Piston fit? This will depend on the pressure you intend to run the engine at and the friction/load on the system. I reamed the bore 6mm and turnêd the piston to a close fit so without lubrication (other than residual cutting fluid) it would fall under it's own weight with an open cylinder and fall in about 10 seconds with a closed cylinder. With light out applied the piston just stayed where it was.

If this link works this is the piston sinking in a closed cylinder:

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and this is the engine running:

**LINK**

Best regards

Roger

I have built a metric version of Phil Duclos' Huff and Puff breath powered engine with 6mm bore and 6.3mm stroke. The cylinder and piston are brass and the piston rod and piston valve are ground stainless steel. The build log is on the Model Engine Maker Forum but you need to be a member to see the pictures.

Thank you