Here is a list of all the postings Roger B has made in our forums. Click on a thread name to jump to the thread.
|Thread: Hobbymat lathe - couple of questions|
The lathe is still in production in the Czech Republic and Pro Machine Tools are the UK agents;
They may be able to help with change wheels.
If you can manage German this company also claims to offer spare parts;
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)
|Thread: Which ignition system for 1/4 x 32 spark plug|
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.
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.
|Thread: Unimat milling tables|
They are still available, but not cheap.
|Thread: Piston/Cylinder Materials|
The Dutch engine builder Jan Ridders has produced several designs with glass cylinders and graphite pistons. This is a flame licker:
And this is a 4 stroke spark ignition version ( the article did carry a warning to run it behind a protective shield):
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:
and this is the engine running:
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.
|Thread: Hobbymat tumbler gear instructions|
I have put some pictures in an album called Hobbymat. The reverser was fitted to the lathe when I bought it. It appears to offer a reversible fine feed but for screwcutting I have always gone back to the original pieces.
If this is what you have I am happy to dismantle things and take more pictures/measurements.
I have a Hobbymat fitted with the tumbler reverse so I can supply pictures and measurements if this is of any help.
|Thread: Crystal Ball Gazing|
A few graphs have been posted on here which deserve some comment. As others have already noted how valid is this data?
Dave (SOD) posted global sea temperatures going back to 1870. Using Hadcet as a reference the time around 1870-80 looks to have been cold so choosing this start point will accentuate the temperature rise. The other question is how valid is the old global sea temperature data? This was taken from ships so would tend to be surface or close to surface data. There would have been significantly more measurements in the North Atlantic than in southern seas at this time which may also bias the results. Searching the NOAA website I couldn’t find any more details. Maybe Dave has some.
Not Done it Yet linked a NASA graph on CO2 levels, once again with no real details. The historic values in the graph probably come from ice core samples as they look similar to the Vostok ones:
More details are here:
The recent data is probably taken from the Mauna Loa series. Is it reasonable to fuse two separate sets of data for CO2, one taken from Antarctic ice and one taken by an active volcano in the tropics? How have the two sets been equalised?
Neil’s graph, as others have noted, has no validation at all. It looks similar to Michael Mann’s original ‘Hockey stick’ which was quite controversial. Skeptical Science attempts to defend it here:
How many on here actually look at the data behind the Climate/Fossil Fuels problem rather than just following the media?
Here is the Central England Temperature series (HADCET) held by the Met Office:
This is the longest existing measured temperature series and shows some interesting points. The temperature rose by more than 1.5°C between about 1700 and 1730. The temperature rose around 1°C between about 1975 and 2000. Were those both man made, both natural or what? Since 2000 the temperature has been fairly stable but at a higher level than before. No sign of the catastrophic rise that that the ‘people on the streets’ are protesting about.
The next graphs are of the Global Temperature series (HADCRUT):
The various temperature series gathered on these graphs are in reasonable agreement but they only go back to 1900. If you look at the Central England series quite a lot happened before then. There is also a significant difference between the north and south hemispheres. For the northern hemisphere there is somewhat dubious attempt to show an increasing rate of temperature rise by starting from a cool spell in the 1970s. Ignoring that the average temperature rise is around 1°C per century. The steeper slope from 1980 is around 2°C per century, but only for the northern hemisphere. There is no sign of any correlation with the CO2 levels, which have also only been measured from 1958.
Once again no signs of the impending catastrophes.
I fully believe that we should minimise our consumption of finite resources and reduce our impact on the planet but it should be done in the right way and for the right reasons, not being controlled by a global circus as it is today. The IPCC’s science is OK but there is none of left once you move into the political scene.
|Thread: hobbymat lathe md 65|
I described the adjustment procedure here:
Getting the optimum setting of all three screws can take a little patience. Does the tailstock move smoothly with very little play? Is there obvious wear on the top of the bed?
|Thread: A close shave or why safety glasses are a must|
Hopper, they are in stock at my supplier but P+P may be a problem
As a glasses wearer I can recomend the Uvex Super OTG.
I often forget I am wearing them when I leave the cellar.
|Thread: edm machines|
There is also some information on Ron's Model Engineering web site:
If you choose 'Resources' on the left hand side followed by 'How to?' You will see a list of topics. 'Remove a Broken Tap' takes you to the pages on 'Making and Using a Basic EDM'
|Thread: Testing for isolation|
If you beleive you have isolated correctly and are prepared to touch it with your hand a short circuit with a screwdriver will be no problem. If you have made a mistake it may save your life. Belt and braces.
|Thread: Proxxon MF70 went bang|
There was apparently a design change in the MF 70 motor so the detail of the part number may be important.
This company offers a possibility:
The parts list is here if you don't already have it:
I have removed the motor from my (probably newer) MF 70. There is a screw either side of the motor and then you have to pull the motor out of the coupling. The older version appears to be more like a gear.
|Thread: Form tool to cut big end / main crank bearings.|
Is the crankshaft cut from solid or a casting?
Are you doing all the turning between centers?
Is it possible to support one end in a 4 jaw chuck to improve ridigity?
|Thread: Siezed Drill Chuck in a Tailstock|
This is going back a long time but I think it was quite deep, 25-30mm. If you have a MT1 something with a tang on it it will give you an idea of how deep the taper in the quill is.
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