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Member postings for Roderick Jenkins

Here is a list of all the postings Roderick Jenkins has made in our forums. Click on a thread name to jump to the thread.

Thread: Another workshop insulation question
20/09/2018 22:03:35

OK. I've done some sums. Celotex/Kingspan is certainly the way forward. Concrete block / 50mm Kingspan / 11mm OSB gives me a U of 0.4 which is poor compared with a new build wall requirement of 0.16 but not too bad compared to a refurbishment which the regs seem to allow to be 0.3 to 0.55 (if I understand it correctly).

I've bought a pallet (25 sheets) of 50mm Kingspan seconds from these people **LINK** for £432 delivered which should do the job. I'll keep you posted.


19/09/2018 20:36:21


No problem at all. My moving situation is very similar to yours. I just managed to take some pics of the garage before the removal guys filled it with my stuff. I'm doing some comparative U value calcs at the moment - I'll report back in due course.



19/09/2018 18:07:37
I was just waiting for someone to spot the missing 'at'. Why am I not surprised it was you 😉
18/09/2018 19:49:42

We have just moved to sunny Christchurch in Dorset. The new workshop is considerably bigger than my last home, being 5m x 5m.





The plan is to replace the up and over door with a 2/3 1/3 side hinged door.. The walls are single skin, mostly concrete block but with a brick front, semi detached on one side - all painted now. Reading the various threads on the forum have led me to plan to batten the walls and infill with 25 mm polystyrene, then use a polythene vapour barrier and line out with OSB painted white. I'm less clear on what to do with the ceiling. I'm currently inclined to go with Celotex (or similar) fastened to the rafters (thus making use of the reflective surface to enhance lighting). I understand that It would be a good idea to ventilate the area between the Celotex and the roof boards - how would I go about this? Any other comments on the scheme would be most welcome.



Thread: Beer and Grapefruit
13/09/2018 23:09:40

I seem to be one of those people who are particularly sensitive to bitter flavours. I find many craft beers (and sprouts!) far too bitter for my taste - there seems to be something of a competition for hipsters to make beers as bitter as possible. A nice , malty pint of best for me. I was brought up on Wadsworth 6X and Brakespear.


Thread: Cyclone Vacuum Separator
12/09/2018 21:47:15

Dyson have made a living from domestic cyclones. Not sure where their various patents came from since the technology is old. They do work though and the filters don't clog like a conventional vacuum cleaner.


Thread: My Digital subscription
06/09/2018 18:10:43
Posted by Neil Wyatt on 06/09/2018 16:51:57:
Posted by JES on 06/09/2018 16:27:38:

I would like to ask a question on this forum. I am trying to read the magazines from the ME site but all I am Getting is a blank grey screen after a message to swipe the screen for page turning. I am using Firefox on a Samsung tablet.

Has anyone got any ideas as to how I can get to the Archive?


You may need to load a flash plugin or enable flash in options.


I use the Puffin browser to read the archive on my Samsung tablet (as recommended by JasonB)


Thread: Centaur engine timing gears
03/09/2018 23:35:38


As you know, ETW was, in fact, very vague about the size of the gears and we can't be sure that he got it right. I made the "correct" skew gears for my Wyvern and still had to relieve the bracket to give clearance for the driven gear to rotate. I still revere the man though and I'm sure you will end up with a splendid engine.

Enjoy the journey,


03/09/2018 18:17:24

I'm not sure that the criticism of Reeves is justified. ETW specified skew (helical) gears that had differing helix angles ( approx 60 and 30 degrees) such that they were the same diameter. This allowed the gears to fit nicely in the space he designed (probably ! ) The only readily available helical gears are 45 degrees so a compromise has to be reached. If you have found 45 degree gears that fit then it is possible that the gears will be too small for the load they have to carry (but I doubt it). Basically, Reeves have offered one solution (perhaps the same DP as the original gears but both 45 degree helix angle rather than a 30/60 pair). You have chosen a different solution - neither is correct according to the original design.



Thread: Good Grief, I Spy Sitting Bulls
30/08/2018 17:02:11

And all worth reading. keep 'em coming...😀


Thread: Cheap chinese Involute gear cutters
29/08/2018 19:26:10

I've had a couple of sets of small Module gear cutters from CTC and have been perfectly happy with them.


29/08/2018 15:10:41

Hi Matt,

Module is the metric way of specifying gears. There is a direct equivalent to DP sizes, just divide 25.4 by the Module. Thus M1 is 25.4DP and M.4 is (25.4/0.4) is 63.5. The tooth form is still involute but if you use Module gears you will need to change the design to cope with the size of gears you will cut although, e.g. 0.8M at 31.75DP is probably close enough to 32DP not to be a problem. You will note also that the cutter number is the other way round from the DP (Brown and Sharpe) notation where a #1 cutter >135.



Way, way too slow - sorry to reiterate the good advice above.

Edited By Roderick Jenkins on 29/08/2018 15:13:15

Thread: Solder..?
23/08/2018 23:36:51


You'll note that I said "suspended" in water. Being an empirical sort of guy I have just measured a cut off a rectangular steel bar and calculated the vol at 94.67 cc and weighed it at 737g. This gives a density of 7.79 which seems reasonably correct for mild steel. I then suspended the bar from a thread and lowered it into a bowl of water that was sat on a tared scale. The indicated weight was 95g which equates, to sufficient accuracy, to 95cc. I'll let you do the algebra, I can't remember how.



23/08/2018 15:39:28

Density should sort it out. 60/40 lead/tin has a density of 9.7 whereas 40/60 lead/tin has a density of 8.9. Weigh the solder in air then weigh it suspended in water. Density is the dry weight divided by the wet weight, all in grams. MEW 251 explains all.



Thread: Metric threads on an ML7
21/08/2018 17:11:19
Posted by John Haine on 21/08/2018 16:54:18:

On my S7 the bolts holding on the LS bearing brackets are I think 4 BA. There's a row of holes on the back of the bed to attach accessories which I was surprised to find were M6 - now I realise they must be 0 BA.

Myford generally favoured 1/4" BSF rather than 0BA but that may depend on the age of the machine.



Thread: shoe sole glue
16/08/2018 11:34:02

Shoe Goo is very good. It will even build up worn heels if you make a dam with some insulating tape.



Thread: What did you do Today 2018
12/08/2018 21:59:16

Posted by Andrew Johnston on 12/08/2018 21:47:43:

... At least I'll be able to say it's me wot made it, instead of buying a casting.

thumbs up That is very important


12/08/2018 18:05:09


I think you are wise to try out on a bit of ally first. My attempts at this sort of thing with a 1mm cutter were a bit disappointing, the lack of sharp corners, particularly on the "N"s showed up rather badly. My thought was to go around again with a pukka engraving cutter but I really run out of the necessary speed on my little CNC mill.

Gòod luck,


Thread: Some beginner questions regarding knurling tools
10/08/2018 16:54:15

The first thing I would do with a small lathe is to put it into back gear, you will need lots of torque. My usual technique with a scissor knurl is to start with only a third of the tool width clamping on the job. I introduce the tool to the job and adjust the wheels so that they are finger tight on the diameter of the job. I then withdraw the tool and tighten the tool by about a quarter turn. Switch on the lathe and then advance the tool with the cross slide. This should produce a good pattern. Once the pattern is set then the tool can be advanced towards the headstock with the leadscrew.



Thread: Issue 269 Temperature Controller Article
10/08/2018 11:02:32

I've given up using the degree symbol. In the context of model engineering or, indeed, everyday life 200C or 300F are unlikely to be confused with 200 Coulombs or 300 Farads.


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