Thursday, 4 June 2020

Why Doesn't My Power Tool Startup?

When a power tool won't power up there are various causes of failure. but troubleshooting should be done in a methodical order, the main thing though is to check the obvious first!

Equipment Needed:


Some screwdrivers, flat and Phillips head
Continuity meter or multimeter to trace continuity from the plug to the motor.


A non-contact voltage detector (optional). These devices glow when the tip is held close to a live cable


https://dengarden.com/home-improvement/Using-a-Multimeter

Important !!!
Remember to avoid shock, disconnect the tool from the mains supply before troubleshooting!!!


Troubleshooting: 


 ● It may be obvious but ensure the socket outlet isn't faulty, try the tool in another outlet to see if it works.

● Check whether the overload circuit breaker if fitted on the tool has activated. This happens e.g. on a table saw when the motor is stalled. To reset you need to press a button. The breaker may need a couple of minutes to cool down before resetting

● If plug is rewireable check for loose screws at plug pin terminals, loose fuses etc. 




● A common cause of failure especially with drills and other hand held tools is one or more broken wires in the power flex caused by metal fatigue in the cable (like when you break a paper clip by bending it backwards and forwards) , this usually happens where the cord leaves the plug or where the cord enters the tool. If you have a non-contact voltage detector, you can use it to trace the break from the plug to the tool. Plug in the tool and hold the tip of the detector at the plug, it will glow here but as it is moved down along the flex it will stop glowing after the break (If the break is in the live core of the cable)

● Sometimes it is possible to detect where a break is in a flex by stretching it, the flex will narrow in the region of the break

● If you still can't trace the fault, unplug the tool. Open it. Check the continuity from each pin of the plug to the switch in the tool.

● A faulty on / off switch can prevent the tool from working. Use the continuity tester to check this

● Loose spade terminals on switches may cause intermittent operation

● Tools with green and red start and stop buttons may have a faulty relay

● The brushes in the motor may have worn down

● The armature or field coils of motor may have gone open circuit. The field coils can be checked with the continuity meter

Tuesday, 19 May 2020

String Trimmer Line

This 0.095 inch diameter (2.4mm), 3 pound, 685 foot spool of professional trimming line manufactured by Oregon should last you years and years. It has a high strength inner core and an outer coating to prevent welding. In other words it is less likely to stick as it unwinds from the spool. The square edges also improve cutting efficiency compared to standard round profile type
Check your trimmer to see whether it is compatible with this diameter line.

Sunday, 19 April 2020

Activities for Kids During the Covid-19 Lockdown: Sowing Seeds

Equipment

  • Some trays, pots, yogurt containers or similar
  • Spray bottle from shower or window cleaner
  • Seed compost or multipurpose seed and potting compost
  • Seeds

Time to sow

For annual and half-hardy annuals, February to April. Check the seed packet.

You can use any types of pots, boxes or proper seed trays

Steps

  1. Fill the containers almost to the top with seed compost
  2. Shake the seeds out onto your hand and scatter evenly over the compost
  3. Don't cover very small seeds. Seeds a few mm in diameter can be covered with a sprinkling of compost. Larger seeds such as sunflower seeds should be pushed about 1/2 inches (12mm) below the surface.
  4. Water with the spray bottle and keep the compost moist. Only water as needed, not everyday. You can use a watering can, but unless it has a fine sprinkler rose, it can flood the compost and wash away seedlings.
  5. Keep the tray in a warm place and cover with a sheet of card to conserve moisture and keep the seeds dark until germination
  6. Once the seeds germinate, remove the card and move to a bright place such as a window sill.
  7. Transplant into pots once seedlings have their first pair of "true leaves" (the second pair of leaves to appear). Once the plants become large enough, transfer to their final location.

Fill tray with compost

Sprinkle seeds from your hand
Transplant seedlings once they're big enough and have two "true" leaves

This is an extract from my article "Gardening for Beginners: 10 Easy Steps to Sowing Seeds" on Dengarden which has lots more detailed instructions and photos

Wednesday, 22 January 2020

Repairing a Heat Selection Knob on a Fan Heater

Well this was frustrating! The range selection knob on my fan heater was turning without doing anything. I decided to try and open the case to see what was wrong, but of course the manufacturer had used security fixings, relatively uncommon triangular ones too!



I have lots of shapes and sizes of Torx bits and screwdrivers, but they would be useless in this situation. Luckily I managed to undo two of four screws from the upper side of the heater using a large jeweler's screwdriver. This allowed me to pull the case apart just enough to remove the knob.


Part of the shaft of the knob had snapped off in the switch. Gluing, even with superglue wouldn't be a permanent fix because the resistance of the switch was such that a large torque was needed to change range.
First I removed the broken-off piece of shaft from the switch using a woodscrew. The piece was hollow as was the other piece of shaft remaining on the knob. I decided to attach the two pieces together using a rivet pin.


I hoard lots of scrap, and rivet pins are part of my collection, along with self tapping screws, springs, nuts, washers and all sorts of other miscellaneous items! Some of these pins were exactly the right diameter.

I dripped some super glue into the hollow interior of both sections and also on the broken surface, then joined the two pieces together. Some heat from another fan heater accelerated curing of the glue.


After trimming the pin, I replaced the switch, cost of repair? Zero!

Monday, 20 May 2019

How Do I Mix Fuel for My String Trimmer, Hedge Trimmer or Chainsaw?

These garden power tools generally have a two stroke engine (also known as a two cycle or 2T engine), and to make them lighter, they don't carry motor oil on board as in the case of a lawn mower or road vehicle. Instead oil is added and mixed with the petrol (gas) before use.
In general petrol/oil ratio for 2-stroke engines is 40:1 or 50:1 which is 2.5% or 2% oil. 50:1 is equivalent to 20ml in 1 litre or just over 2 1/2 US fluid ounces per US gallon. 40:1 is equivalent to 25ml in 1 litre or 3.2 US fluid ounces per US gallon. 

After adding oil, swirl the contents around to ensure it's thoroughly mixed.Consult the manual of the machine for details of the recommended ratio.



Tuesday, 12 March 2019

Homemade Tools - Snow Rake

I put this together from scrap 2 x 1 and 3/8" (10mm) plywood. I used some pieces of waste wire from electric cable (string would be just as good) as ties to stop the board pulling off the end of the 2 x 1.



Tuesday, 5 March 2019

New Science Q&A Article for Children

Just published a new science guide for children.

"Top 100 Interesting Science Questions for Kids" covers space, nature, technology, engineering, elementary math, chemistry, physics and biology.




Sunday, 24 February 2019

AA to C and D Battery Converters

These are useful little gadgets if you don't have any C or D cells to hand. AA cells are readily available in cheap packs from pound/dollar/euro shops and are probably also optimised to have a higher energy density.



Tuesday, 19 February 2019

Snow Shovels by Briggs & Stratton

Think I'd prefer shovelling by hand to warm up, but these snow shovels by Briggs & Stratton could be useful!



Lidl Tools from the Centre Aisle - Air Wedges

Picked up this set of air wedges in Lidl . They're like a mini version of what firemen use. Handy for lifting and positioning stuff and pushing things apart.