Chris Johns
  • Member for 5 years, 11 months
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1 answers
2 votes
106 views
How much air will an engine use per tank of gas?
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4 votes

You probably want to look at stochiometric ratios by mass. However this is a difficult problem to solve from first principals as for an IC engine air is essentially free and monitoring its ...

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1 answers
2 votes
126 views
Clockwork Motor feasibility?
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The fundamental issue is energy density. A spring simply doesn't store that much energy per unit mass and is ultimately limited by the yield stress of the material. Where springs are good is in ...

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2 answers
2 votes
170 views
Stress-resistant, elastic materials
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It depends exactly what application you are looking for. The amount of stress a material will tolerate is defined by its tensile strength and the amount it will deform under a given stress is ...

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2 answers
1 votes
62 views
Equal power transmission in 4x4 vehicles?
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It depends on what type of differential it has. The nature of an open differential (as found on normal road cars) is that the spinning wheel(s) will get all of the torque. Proper off-road vehicles ...

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2 answers
1 votes
57 views
Particle shape of powders
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It depends partly on the properties of the material and partly on the manufacturing process. High quality metal powders used for sintering and powder metallurgy for example are often produced by gas ...

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2 answers
1 votes
70 views
Pouring copper onto another copper block
4 votes

There are a couple of issues here. To get a proper fusion weld both surfaces need to melt and whether or not this happens depends on the details of the heat transfer for the whole system. It is ...

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2 answers
1 votes
222 views
Reynolds Number
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L is described as a characteristic dimension, it's function is to indicate the overall scale of the system. For example in circular pipes it would be the pipe diameter and for a wing you would ...

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1 answers
1 votes
77 views
What are reasons to use cutting speeds different from recommended?
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By necessity recommended speeds and feed rates are generalisations and, in practice the optimum for a given job can vary a lot. Recommended speeds are typically intended to be a reasonable compromise ...

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1 answers
1 votes
276 views
Definitions of strength?
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Strength can mean different things in different contexts and technical definitions can vary significantly from what is commonly understood by the word 'strength'. For structures where actual forces ...

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1 answers
-2 votes
55 views
Is the construction of a high-speed 3D printer (replicator from Star Trek) possible?
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A replicator is a very long way from 3D printing. Although 3D printing is often endowed in the media with quasi magical properties all it really is is multi axis CNC extrusion and not fundamentally ...

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2 answers
2 votes
1k views
Working out functional gear in AutoCad
4 votes

Gear design from scratch is a fairly major process in itself and so the vast majority of gears are made to standardised tooth profiles. Metric gears are usually designed to the module system. This ...

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1 answers
2 votes
137 views
Looking for a device that breaks the circuit if the voltage gets too low
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4 votes

The simple answer is that you can get off the shelf modules which does exactly what you want. They are often called 'split charge modules' and are designed for installations like boats and motor-...

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1 answers
1 votes
49 views
How small can coolers get?
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4 votes

A Peltier cooler would fit the requirements you set out. They can be compact enough to fit the 'wristwatch sized' requirement and use electrical power to achieve the cooling effect. You do still ...

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3 answers
6 votes
7k views
Why are nuts 6-sided?
4 votes

The main reason to prefer hexagons over square or octagon section in general is that hex bar can be held in a 3-jaw self centering chuck which makes it convenient for machining operations. Hex bar is ...

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1 answers
1 votes
144 views
Why is electricity used for powering our device?
4 votes

Electricity is a convenient way to generate power centrally and distribute it to where it is needed according to demand. Central power generation by technologies like steam and gas turbines means that ...

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3 answers
3 votes
225 views
Why is 3D printing with metals so uncommon?
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There are a number of practical processes for 3D printing in metals using various powder sintering techniques as described in other answers. However it is difficult to use the sort of direct ...

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2 answers
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2k views
Materials which withstand high temperatures, and are relatively soft, for chuck jaws
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Carbon fibre or kevlar textile might work as a soft covering on an aluminium backing plate In terms of metals high purity annealed copper might be soft enough on it's own. You can also get self ...

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3 answers
4 votes
439 views
Why are the processes called "Precipitation Hardening" and "Solid Solution Strenghtening"?
4 votes

For most metal alloys tensile strength and hardness are effectively different expressions of the same property. Although this does depend on exactly how hardness is measured and some related ...

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2 answers
3 votes
8k views
Type of motor for a small lathe
4 votes

If money is no object then there are a lot of advantages to using a DC motor for a lathe. The ability to have continuously variable speed control is a huge advantage for a lathe. Compared to other ...

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4 answers
4 votes
307 views
What type of bearing could be used to keep a utensil level while being moved from plate to mouth?
4 votes

One difficulty here is that the masses involved are quite small so you need a very low friction bearing. Many industrial bearings are designed for high loads and speeds with quite close tolerances so ...

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2 answers
3 votes
184 views
3d model gear to fit another gear
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It is important to remember that, when you design a set of meshing gears you need to keep the size and shape of the teeth the same, irrespective of the diameter. There is a temptation to design a gear ...

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2 answers
2 votes
92 views
Setting up a "pulsing" motor?
4 votes

There are 3 obvious solutions mechanical : have a second, continuously running motor connected to either a cam or a rotary contact switch which makes/breaks the power circuit. This sort of approach ...

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3 answers
3 votes
165 views
Transferring heat using a pipe at temperatures below the boiling point of water
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4 votes

The advantage of a heat pipe is that it is a passive way of getting a high rate of heat transfer between two points using a single, compact component. However a heat pipe is only one part of a heat ...

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3 answers
1 votes
126 views
'Length measure' vs. 'length measurement'
4 votes

The usual practice is to refer to measurements on a drawing as 'dimensions'. For example you might say 'dimensions L1, L2 and L3 are determined by calculation'. The term dimensions also implies ...

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4 votes
162 views
Shear rate of a fluid in a container with a sliding PTFE top plate. Will the liquid move with the plate?
4 votes

In order for the fluid to not be affected at all by the movement of the plate it would require either zero friction between the plate and the liquid or for the fluid to have zero viscosity. There is ...

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1 answers
2 votes
1k views
How can dross/slag formation be reduced during aluminum recycling?
4 votes

The dross is mostly composed of aluminium oxide which is already present on the surface of the metal before it even goes into the furnace, as the aluminium melts the oxides separate and float to the ...

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2 answers
4 votes
3k views
Designing non-self-locking worm gear
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Whether or not a worm gear is self locking depends on the lead angle and the coefficient of friction between worm and wheel. It will self lock when the coefficient of friction is greater than the ...

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7 answers
7 votes
3k views
Why does the orientation of a floor joist affect its strength?
4 votes

In the context of engineering calculations this is down to a property called 'second moment of area', the way that this is defined is a bit obtuse but is describing something which is reasonably ...

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2 answers
1 votes
78 views
What mechanisms can be used to move a drum at constant speed without an electrical system?
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4 votes

There are a few ways to go about this. One easily available solution is simply to adapt the mechanism from a mechanical clock or watch. This will give a regular series of pulses rather than a true ...

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2 answers
2 votes
750 views
What are the design principles for risers in sand casting?
3 votes

Casting terminology can vary a bit. My experience is in art casting in cast iron. In my experience with sand casting risers specifically tend to be used as vents to allow gas to escape from the ...

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