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Member postings for Paul Kemp

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

Thread: How not to use a clamp
24/01/2021 11:56:41

Lol I rest my case. Now not only is the bloke being lambasted for poor practice and leading novices astray but now his motives are being questioned as to why he decided to do the job that way in the first place! I am surprised this has not been closed down by the "authorities" early on as it potentially encourages viewing of associated content with reviews of equipment from banned (on this forum) suppliers!

Paul.

23/01/2021 20:42:45

Sometimes I despair at this forum. Undoubtably there is a lot of good stuff but equally there is a lot of pointless bitching, point scoring and willy waving! Ramon, sadly you were lead into a trap here by not having the advantage of knowing what was being done or the purpose of the clamp. I don't see there is critiscm of your postings for actual machining set ups where higher forces are involved but for drilling a 3mm hole if he could have held it steady enough in the right place he could have held it with his hand! Now wait for the rush of critiscm on that last statement!

Clearly I am not alone in thinking the OP posted an extract picture with commentary that was completely out of context to the operation being carried out. For the purpose of what he was doing only a very light clamping force was required and to horse a heavy clamp down hard would have been detrimental to the casting! By all means use a valid example such as where someone is milling something held to the table with chewing gum and sellotape with a 4" face mill that clearly presents a danger to operator and machine but this example does not fit that category!

This whole thread is pointless, the video maker wasn't giving any instruction on how to use a milling machine he was merely showing how he was intending to hold an irregular shaped casting to a plate which could hold it for future ops. At no point did he advise or infer anyone else should follow his approach that I heard and I did go and watch the whole video.

Too many people on here ready to throw bricks when I am sure they probably live in glass houses.

Paul.

Thread: Design of boilers
22/01/2021 13:25:10
Posted by Bob Worsley on 22/01/2021 10:00:49:

The dismal response was aimed pretty well at everyone, the near complete lack of any analysis and thoughtful comment on what took me several weeks to work out.

One person says that the smoke box gets red hot, another says that the boiler is 70% efficient, can't both be correct. Reading old books and they get efficiency readings of about 5%, which I would believe. This is why I introduced the Stefan-Boltzmann law, the boiler radiation losses are probably more than 50% of the heat that goes into the boiler.

I have also just spent several long evening trying to calculate form first principles the theory of staying, and it is now beyond my maths ability, see if I can find another book. I have used the Schaum's outline books but now find them incomprehensible. What is the difference between shear and bending moment stresses? I can understand the shear applied to a rivet, but in a beam?

I see that copper prices have risen over the last 6 months or so by $1000 tonne to $5,500, so probable can't afford to make them now.

Having strongly disagreed with Bob in the past on various posts related to boilers I think there is small merit in his questions. I am sure with small changes such as flue diameter or even spacing there could be improvements to be made but those improvements unlikely to be in the measure of 10's of percent and probably limited to decimals of percent. Gaining better understanding of exactly what happens at our small scales can only be beneficial and others have trod the road before and not concluded there are significant gains to be made. Maybe that is because efforts have been concentrated on improving the standard fire tube, locomotive style boiler on which there is much full size information to draw from over many years rather than moving to a completely different style of boiler - which is difficult if you want to build a model of something that looks like it's full size counterpart! Maybe he should add brick arches to his list.

i agree that the calculations from first principles for staying of flat surfaces is indeed complicated. There are empirical rules of thumb and simplified formulae available and indeed tabulated 'standards'. The figures for fos quoted In the linked spreadsheet on a similar recent thread for the stayed surfaces of up to 70 indicate (if the underlying calculations are correct) just how conservative the solutions adopted in miniatures for stayed surfaces are when compared to quoted fos of around 3 on the circular barrel. The key for stay pitch is the resistance to deformation of what is effectively a constrained plate where due to the pressure one side is in tension and the other in compression and where the stress in the plate is sufficient to generate plastic deformation. SOD's reference to FEA in CAD would certainly save a lot of manual number crunching!

Paul.

Thread: BSF vs BSB threads
22/01/2021 01:31:01

I would say they are the same without getting the books out but I am sure someone will be along to disagree lol.

Paul.

Edited By Paul Kemp on 22/01/2021 01:31:52

Thread: Model boiler safety calculations
19/01/2021 21:20:41

I started typing a contribution yesterday but this dumb site logged me out in the process so I lost it and then lost interest.

For Andrew you should ask your inspector for the specific calculations he requires - as he asked he must know? I suspect he has asked due to the requirement in the test code which is fair enough but you could then ask him against what standard he will be assessing the results? Assuming he is competent to assess the results then he should also be capable of doing the numbers, do maybe ask him if he wouldn't mind doing them for you?

There seems to be an assumption that for the published designs calculations have been done? Has anyone seen the supporting calculations for these designs? In fact do any of the published drawings bear any evidence they have been assed or approved by a notified body or in fact any body outside the publisher?

Jason, I don't have that particular book, any chance you could pm me the formula therein for stay spacing? I used to have one from the Indian regulations of all places that seemed to give sensible results for larger scale miniature boilers but I have lost it and the web site I nicked it from has been deleted!

I don't disagree with the comments regarding the Australian code but not convinced we just need a direct copy as it is restrictive on working pressure for steel boilers and I understand prohibits some of the established boilers in use here with proven safety records such as the Simplex design.

SOD, 2 X wp and 1.5 X wp tests are industry standard derived from stress fos.

Paul.

18/01/2021 23:43:10

Bazyle,

I would be very happy to see your formula from first principles to provide the pitch of stays. Agreed most of the shell calculations and size v number of stays is pretty basic but I think the calculation to prove resistance to quilting between stays of a flat plate is more complicated?

Paul.

Thread: Marine Engine Flywheel Fixing
18/01/2021 20:56:43

I don't think many decent sized marine steam engines had flywheels, instead they relied on the inertia in the shafting and prop and were flange drive. All the large marine diesels I have worked on have had flange mounted flywheels, no keys just fitted bolts and high torque.

If a flywheel were fitted to a small marine steam engine I would expect it would be secured with a taper gib head key. That's how traction engine flywheels and line shaft pulleys etc were retained, having had to remove some I can vouch for how tight they can hang on! Either that or mounted on a taper on the end of the crank in the same manner shaft couplings are (both with and without keys) the modern type of taper coupling using oil injection to seat and remove are a thing to behold, they can come off with a significant bang and not something you want to be messing with without some restraint in place.

Paul.

Thread: New Member Kent
17/01/2021 19:14:03

Andrew,

Gauge for loco's (larger scale anyway) is generally the distance between the rails, common sizes are 2 1/2", 3 1/2", 5" and 7 1/4"

Traction engines generally are scaled by 1" to foot so 1" scale is 1/12 full size, 1 1/2" is 1/8 full size, 2" is 1/6 full size, 3" is 1/4 full size, 4" is 1/3 full size, 6" is half!

Unfortunately the size of the model is not always a good guide to scale as with railway loco's narrow gauge prototypes are common and a 2" scale ploughing engine will be close to the same overall dimensions as a 4" scale small steam tractor!

If you want to steam any of them you will need a boiler test to get insurance to run them in public. Even if you want to use them in private it's a good idea to at least do your own pressure test before lighting up! Check any paperwork your dad may have had, it may be they have been previously tested which will make re test easier!

Paul.

Thread: Myford super 7 lathe tripping consumer rcd
02/01/2021 11:26:13

I had a similar fault develop on the ML7 after turning a lot of cast iron. It has the I assume original Brook Compton motor with air vents and it sucked in a load of cast iron dust which accumulated in the terminal box. Opened it up, blew it out, problem solved.

Paul.

Thread: What air compressor should I buy?
27/12/2020 14:07:52
Posted by not done it yet on 27/12/2020 13:31:35:

All female BSP are parallel. The male threads could be either. Low pressure is often taper (fitted with a filler and jointing compound or with PTFE tape. High pressure installations usually include a rubber inserted washer as the seal (Dowty washer).

Sorry incorrect, all female BSP threads are not parallel, they may also be tapered. You may use a tapered male thread in either a parallel female or tapered female thread these are accepted as sealing on the thread with an accepted compound. Parallel male threads are not considered as sealing on the thread and should not be used with tapered female threads and as correctly stated are sealed with a conforming washer.

Paul.

Thread: Size question
20/12/2020 20:55:22

Treat it as 3.5" between the rail heads on the straight, depending on the radius curves you might be thinking of using then you might want to consider gauge widening of the track on the curves, the amount depends on the wheel base of the loco's you are intending to run. For example a short wheelbase 040 would probably cope with an 8' radius in 3.5" but a 6 coupled might need the gauge pushing out by up to 1/8" if you want it to go round the corner! For example a 6 coupled 5" gauge loco won't go round much less than a 30' radius curve without slight gauge widening. The back to back dimensions of your wheel sets will also govern points and check rails. Best to go with a standard, there are a few around certainly for 5" gauge, if you can't find one for 3.5" then you can scale it within reason.

Paul.

Thread: Milton Keynes Metals?
20/12/2020 13:50:42
Posted by Frances IoM on 20/12/2020 12:02:14:
shopping partner - probably same way this site attempts to drop a farcebook tracker - money.

Spot on I suspect, I am sure to become a shopping partner all you would need to do is cough up. Is there any past partners that were 'struck off' for quality issues or negative feed back on the site?

Thread: 3 Cylinder Lubricator
16/12/2020 00:39:32

Never had much luck with my 5" gauge modified Speedy feeding both cylinders from a single lubricator. Solution was a tank divided in two with a pump in each half. I can now monitor easilly both cylinders are getting oil in roughly the same amounts. I don't see why you couldn't make a three element lubricator in a single divided box? Would give confidence and peace of mind!

Paul.

Thread: Electric vehicles
23/11/2020 17:57:55
Posted by not done it yet on 23/11/2020 07:22:06:

I am not sure what point you are trying to make

The point you conveniently missed is that battery refurbishment is possible now. It is in its early stages of development but may well be routine in ten/fifteen years time with cheaper, better batteries and more easily/quickly accomplished. We don’t know any facts around this person’s purchase. Was he someone who did not check out the facts, before rushing out to buy one? Did he actually buy it for “peanuts”? Was he clever or stupid less clever?

Anyone who checks out the Nissan Leaf history should know that it has no active battery temperature control. It is ‘old hat’ and past its sell by date. It was the first real attempt of a BEV. They got the battery management system wrong (and still have not corrected it now). I would not touch a Nissan Leaf with a barge pole - there are so many far better vehicles out there. I see they are now being very heavily discounted. New ones with a much larger battery pack for little over twenty grand.

That taxi in the video was deemed worthwhile to improve for its further use? It also clearly states the kit could be installed by the owner, if they so wished (and had the expertise to do it).

I’m not sure if the maths above is water-tight. Why have a replacement battery and a extra half battery to bring the performance back to normal? However in ten years time, things will change. The ‘million mile battery’ will be here as a norm? Batteries will be cheaper (in relative terms). Batteries will not use expensive metals such as Cobalt. Development continues at a pace. New vehicle costs will fall.

Here is a tip for you all. Buy one that you can normally maintain between 80% and 20% charge levels (only use the top and/or bottom 20% when particularly needed) and charge at a medium rate - neither the ultimately fast nor the ‘granny’ cable.

ICE vehicles have had 120 years to develop and improve their drive trains. Time for a change as we cannot continue to burn fossil fuels as we have since the industrial revolution began. Get real and start to change the environment for your children and their children.

Over 100 years ago treadle lathes were quite common? Who makes one now? How many petrol-driven lathes do you know of? Are Luddites still common? Have you read about the Teslas which have covered half a million miles?

The UK is a relatively small place. Most cars could be electric, even now. There are reasons why they are not, but it will change. Nearly all cars will be electric in about thirty years time. Get used to it, even if it will not directly affect you.

Small wonder "I conveniently missed it" as your elaboration that battery refurbishment is available now didn't appear to be specifically mentioned in the original quote and the point being made by the previous poster was not the potential of being able to get a replacement or even a refurbished battery - but the cost.

"Look at this video. But do remember that battery repairs/replacement/improvement/prices/etc will change as BEVs become more widespread."

In fact "battery" recycling by the likes of Corvus is well underway already outside the automotive industry where batteries are refurbished by replacing defective cells and the refurbished units re-deployed to less arduous duty cycles than their first application - good business for them as they essentially get to sell the same 'battery' twice!

Something you appear to be missing when you are telling all to "get used to it" is the majority of responses on this thread acknowledge change is coming but are highlighting the challenges that need to be overcome in the next 10 to 15 years. Given the infrastructure changes required to support battery electric vehicles I can't fully agree with your statement "nearly all cars will be electric in about 30 years time". I can agree the method of turning the wheels may well be electric motors but in my opinion they will be mainly supported by hydrogen fuel cells and not batteries. Better power density and volume density (dependant on compression) than batteries, more convenient and most similar in refuelling as vehicles are today, less down time for refuelling but more importantly less infrastructure investment required at distribution level. Lastly to return to SOD's energy storage issue is energy is more easilly stored in a gas than as electrons in a battery and it doesn't involve child labour in mining to do it.

Paul.

23/11/2020 01:14:55

Ok just found some prices for Muxan they do the range extender for £5352 plus vat plus fitting and a replacement for the old battery is £8028.45 so to bring the 8 year old car back to full performance with an enhancement in Chris's case would be £13,380.28 plus 20% plus labour (if we take labour as 8 hrs at £30 an hour which is dirt cheap) gives a grand total of £16,344.34.

No idea of the value of an 8 yr old leaf but spending £16k on top of buying one to get a car that does 160 miles between charges sounds an excellent deal to me............................. not!

Paul.

23/11/2020 00:58:28
Posted by not done it yet on 22/11/2020 21:54:24:
Posted by ChrisH on 22/11/2020 19:53:30:

You all seem to be flailing away quoting journalistic hype and projecting forward by 15 years!

Look at this video. But do remember that battery repairs/replacement/improvement/prices/etc will change as BEVs become more widespread.

**LINK**

NDIY,

I am not sure what point you are trying to make? They fitted more batteries, increased the weight and extended the range - I don't think anyone has said this is impossible? Chris's point as I saw it was the cost and that was the thing missing from the video linked - no mention of cost. Also It relies on the original battery still being good, I think when they checked the range before connecting the extender pack they said 70 miles? Therefore the existing battery wasn't in bad shape. Connecting a new pack to a knackered one would not have the same effect.

Paul.

22/11/2020 20:29:31
Posted by V8Eng on 22/11/2020 20:20:08:

Browsing another forum I was reading about the idea of equipping lampposts with EV charging points.

That got me thinking about some local roads with victorian terrace houses (now called cottages), the roads are fully parked on both sides because the cottages do not have anywhere else to park and most have more than one car

Counting the number number of lamp posts I reckon it works out at roughly one post to every nine houses, many issues to be overcome in places like that over the next few years!

Edited By V8Eng on 22/11/2020 20:21:56

Exactly like where I live. Such is the commitment and degree of forward planning that the County Council are currently for the first time in 30 years breaking out the pavements and kerb stones and renewing them - shame they didn't take to opportunity to collaborate with the power and interweb companies to at least lay cables for fibre to house and kerb side chargers! It won't be 10 years till they have to dig em up again if the 2030 plan comes to pass!

Paul.

22/11/2020 20:15:43

pgk,

Thanks for the info on chargers, where people have electric heating, cooking etc I would guess 16a will be about the limit of spare capacity on the domestic fuse!

Paul.

22/11/2020 20:13:14
Posted by Steve Skelton 1 on 22/11/2020 17:07:10:

Some were mentioning that gas boilers and gas networks are due to be ripped out. This is probably a premature statement as the industry are looking at introducing hydrogen into the main gas network with a long term potential switch-over to a non-carbon based gas system.

The government just hasn't woken up to this yet!!

See https://www.smart-energy.com/industry-sectors/new-technology/hydrogen-can-be-distributed-in-britains-gas-networks-new-study-finds/

and

https://www.homebuilding.co.uk/news/worcester-boschs-hydrogen-boiler-prototype-enters-first-field-trial

Steve

Steve,

The govt have woken up to this, I attended a virtual hydrogen conference last week just before Boris made his green speech (which didn't get much media coverage!) and hydrogen was number two on the list. There is a project seeking a town to be converted to hydrogen in the gas network very soon. As someone else said, nice idea but I think the fire service may become busier again! I wonder what flavour they will make it so people are aware of leaks. The only saving grace is the band where hydrogen is actually explosive is quite narrow, still burns though!

Paul.

22/11/2020 12:40:21

S.O.D,

The issue of cost of green electricity may not be an issue in the static domestic or industrial setting but it is an issue to use it in a mobile setting like vehicles or boats. The cost of the electricity at the static transfer point can be cheap but the cost of the equipment required to put it on wheels is significant.

Wind farms also are not completely unmanned, all the coastal wind farms have significant maintenance bases with daily deliveries of techs to the turbines. It would be interesting to compare man hours per kWh between a conventional power plant and a wind farm I have no idea what that may be but would agree it's very likely lower for wind but large scale wind is definitely not fit and forget. Probably the least labour intensive post commissioning is solar?

As you rightly say matching generation with demand and the need for storage is the difficult bit and that is where the costs rack up.

Paul.

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