Welding modern star pickets

I was chatting with a chap the other day, and he said “pity you cannot weld star pickets anymore” wanting to raise an existing fence 600mm to try and keep kangaroos out.

You can buy a section of star picket with a socket to put on top of an existing picket, but they are quite expensive.

So, the problem arises because a lot of star pickets sold in Australia in the last 20 years or so are made in China from “rail steel”, a higher carbon steel (~0.6%) that allows thinner section, less weight, lower transport cost etc.

If you arc weld these with ordinary general purpose electrodes (E6013 in Australia), they are likely to crack and fail under load.

I have used two options:

  • stick weld with E7018 2.5mm electrodes; or
  • MIG weld with AWS A5.20 E71T-GS 0.9mm flux cored wire.

To extend an existing picket in situ, you can lap the extension and do two vertical welds, or but the sections (see jig below) and do horizontal three welds.

Above is a jig using a short piece of water pipe and two locking chain clamps. Of course you would straddle the join to clamp the pieces and remove the jig after two welds are completed. Continue reading Welding modern star pickets

Repair of the valve of a Dramm “touch ‘n flow” water wand

I have a Dramm “touch ‘n flow” water wand, a moderately expensive thing which worked very well, except that like so many similar things, the lever valve failed after a few years of age, but little use I might add.

Above, the wand. Note that the handle is molded rubber over some structure that contains the valve… it is designed to be unserviceable. Continue reading Repair of the valve of a Dramm “touch ‘n flow” water wand

Toro (Loncin) 24.5HP V-twin spark plugs and crossfire

I recently replaced the spark plugs in a Toro (Loncin) 24.5HP V twin with new non-resistor plugs, the original were Champion RN9YC resistor plugs. The replacement was solely scheduled maintenance as per the book.

The engine was then difficult to start, it took a long time cranking and often backfired whereas previously it had started quickly and certainly. Low speed idle was rough and slow.

So, could the non-resistor plugs be the cause of this sudden change?

A pair of new NGK BPR6ES (resistor plugs) was installed and the engine starting was restored and idle speed was smooth and book speed.

So, the non-resistor plugs did look like the problem, and being of an enquiring mind, I captured the HT waveform with one resistor plug and one non-resistor plug (#2).

It was again difficult to start and idle was slow and rough.

Above is the capture, red is #2 and blue is #1. The lack of symmetry can be seen, there is a distinct blue spike at the beginning of the red burn phase. It seems like the red spike (non-resistor plug) that caused the spark burn has somehow triggered an impulse on the blue circuit. Continue reading Toro (Loncin) 24.5HP V-twin spark plugs and crossfire

200h maintenance – Toro MX 4250

My Toro MX 4250 residential zero turn mower, has 200h of service over 8 years… which is not very much.

Above is a recent capture of battery voltage (red) and battery current (blue) using a Hantek 1008C that was under evaluation. (The image colours were inverted for the article.)

Valve lash measurement

Starter current measurement hinted that valve lash was incorrect in at least one cylinder

The exhaust valves should be 0.15-0.2mm lash, and were measured within that range for one cylinder and between 0.2 and 0.25mm (Cylinder #1). This probably accounts for the difference in cranking current at compression, the compression relief is degraded by excessive valve lash.

The inlet and exhaust valves were adjusted as needed.

Above is a capture of starter current after the valve lash adjustment. Note that the peaks in each pair are approximately equal.

Spark plugs

Spark plugs were removed and inspected. The gap was good, the electrodes had sharp corners, Nevertheless, new plugs were reinstalled (per the service manual).

Leak down test

A leak down test was conducted using an OTC 5609. Leak down was less than 1% @ 400kPa in both cylinders, excellent.

Oil change

Oil and oil filter changed.

Fuel filter

Fuel filter changed.

Air filter

The prefilter was washed and re-oiled. The paper cartridge was pretty clean, but was blown out with compressed air.

Control dampers

The right hand control damper is not effective, and sufficiently bad to impact driving.

Replacements are unavailable at this time.

Toro MX 4250 starter current captured using a Picoscope

A recent exercise was to become familiar with a recent acquisition, a Picoscope USB oscilloscope.

It has quite different software to those of other USB oscilloscopes that I have used, so a bit of learning and adaptation.

The test scenario here is capture of battery current and battery voltage whilst cranking my lawnmower which as a 24.5HP V twin petrol engine.

Above is the captured data expanded to explore the initial part of cranking (with disconnected spark plugs). Continue reading Toro MX 4250 starter current captured using a Picoscope

Mower deck maintenance – Toro MX 4250

The deck is a fabricated deck on a Toro MX 4250 residential zero turn mower, it has 200h of service over 8 years… which is not very much.

The deck has the recycler option installed.

Deck service included:

  1. Fit new bearings to spindles;
  2. Replace both idler wheels (components are not serviceable);
  3. Clean and apply corrosion protection under deck;
  4. Procure, fit and balance new blades; and
  5. Procure spare drive and deck belts for spares.

Spindle bearings

Jiggling the blade tips showed 2-3mm vertical play in both spindles. New bearings have much less play, undetectable without instruments.

The spindles are easily serviced.

The lower bearing is one spindle had a rusted retainer / separator and collapsed when driving it from the housing. The other lower bearing was rough, but did not collapse. The top bearings were in good condition.

A set of four NSK 6203-2RS bearings was purchased ($35) to replace all the bearings.

Idler pulleys

Both idler pulleys were dry of grease. It was possible to pop the rubber seal and pack a little more grease pending arrival of replacement parts.

Replacement parts were purchased for $60 (inc shipping) and fitted.

The message is that water sprayed over the top of the deck assembly is retained in a shallow cup on the sealed bearings and some will wind up inside the bearings… don’t wash the top of the deck.

Deck clean, descale and corrosion protection

Above, the underside of the deck after washing, de-scaling with a pneumatic needle scaler, power brushing with a cup brush, and another high pressure wash ready for application of corrosion protection. Continue reading Mower deck maintenance – Toro MX 4250

Re-engine of Deutscher 650 chipper shredder

The article documents replacement of the engine on a Deutscher 650 Chipper Shredder. The original engine was a Briggs & Stratton Intek 206 single cylinder four stroke petrol engine which has accumulated 200 hours over 10 years use.

During that time, it had regular oil changes, air filter changes, new carburetor seat and air filter gasket, as well as frequent cleaning with compressed air to ensure the air cooling was fully effective. It passed a leak down test of valves and rings at 200h, then valve clearances were checked and were spot on… no adjustment needed. (Note that the engine was never run on Ethanol fuel.)

Additionally there is ongoing belt maintenance (adjustment and replacement) and blade sharpening / balancing.

Replacement parts were expensive, the seat alone from eBay was over $20, spark plug over $20, the air filter gasket was over $40. Air filter sets were quite cheap on Aliexpress.

It gave good service, and was reliable. Approaching 200h, a decision was made to replace the engine with a Chonda to minimise the risk of failures (like plastic camshaft gears, lobes, compression relief).

Basic fit up

Above is the Deutsher 650 Chipper Shredder. Continue reading Re-engine of Deutscher 650 chipper shredder

Karen’s Victa

Karen purchased a Victa lawnmower many years ago, and it has expired.

Victa was Australian, but now owned by Briggs & Stratton. The engine is different to most two stroke small engines, the notable differences are:

  • Victa’s G4 plastic carburettor; and
  • the engine is built “upside down”, the flywheel is underneath (ie on the PTO end), and there is no main crankshaft bearing above the big end, the crankshaft is supported by two bearings below the big end.

This article describes the service work to get the mower into good working order.

First checks / observations

The handle bolts and handwheels don’t work, someone has replaced a cup head bolt with a screw and it does not locate in the tube, so a screwdriver is needed to tighten the handle. The lower bolts are loose and need tightening.

The mower takes a lot of effort to push, the wheels are jammed up with string and stuff binding the bearings.

The blades are beyond service life, chipped and blunt, and the blade carrier and mower base are caked with wet decaying grass clippings.

Fuel tank contaminated with solids and water.

This is an air cooled engine, and the cooling fins and cooling fan were caked with oily grass / dust residue. This leads to higher operating temperature, shorter engine life, and performance problems.

Above, the air filter is filthy and will cause rich running which results in carbon build up in the combustion chamber and blocked muffler. Continue reading Karen’s Victa

Hot water woes

A recent episode where the 170l gas storage hot water service relieved itself through the pressure / temperature relief valve sent me on a quest to understand the problem.

At the time, a ‘full rate’ discharge of 95° water was holding the valve open, and even with the gas turned off, the flow continued for some time until I closed the water isolation valve to let the system cool down.

So, was this simply a thermostat failure, temporary or permanent, or perhaps the result of ‘stacking’.

Stacking is caused by repeated very short draws of hot water, which cool the bottom of the tank near the thermostat, triggering heat input which can cause the top of the tank to reach temperatures considerably higher than the set point of the thermostat.

Another question that was of interest in choosing a replacement if needed, was how much heat is lost from the heater, what is the running cost of heat leakage alone.

Heat leakage

The heater was allowed to reach ‘normal’ operating temperature and stabilise, and the gas valve was closed which would allow the unit to cool.

A variation on my IoT water tank telemetry project was configured to use a type K thermocouple and 4-20mA converter to provide a temperature logger, a type K thermocouple was inserted between the insulation blanket and tank at the top of the tank. The 4-20mA converter does not incorporate cold junction compensation, but the logger incorporates an ambient temperature measurement facility which will be used for approximate compensation.

Above is the improvised data logger setup. Continue reading Hot water woes

A mid life kicker for the 2500VA 230V 50Hz genset

About 10 years ago I purchased a 2500VA genset on eBay for about $250 incl delivery. It turned out to have wiring problems behind the control panel, and required an hour’s work to fit some new wires and terminations and make it safe. The seller refunded $80 as compensation.

It has what appears to be a genuine Honda GX160. Now I bought it with I must say a great deal of skepticism, but having worked on many Chondas (Chinese Honda ‘clones’) this is undoubtedly a class above, and I think on all the evidence available, it was a Chinese manufactured Honda destined for the domestic market. Continue reading A mid life kicker for the 2500VA 230V 50Hz genset