Spare parts and maintenance tips
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General Comments It seems the general design and build quality of the Dynamow are pretty bomb proof. The hydrostatic drive system is very simple and does not contain any hyper-expensive components like many other hydrostatic mowers.
How does the hydrostatic drive work? Simple. The engine drives a hydraulic pump by a concealed belt. This pump delivers hydraulic oil from a tank on top of the cutting deck to a hydraulic valve in the left chassis member. This valve is connected by a bowden cable to the accelerator pedal. The further the pedal is depressed the more the valve opens and the faster you go.
The fluid passes from this valve through hydraulic pipes within the left chassis member to the forward/reverse valve situated at the base of the steering pyramid cover. This valve is controlled by a lever under the steering wheel.
Then flexible pipes connect this valve to a Danfoss hydraulic motor above the front roller which drives the roller through a simple bike chain on two sprockets. Don't worry if the drive motor is rusty like this one. It's a very thick casing and would take about 200 years for corrosion to get inside.
The plastic pyramid, which gives the Dynamow it's classic shape under the steering wheel, is home to the pipes from the forward/reverse valve to the motor and gives them room to flex as the steering is turned 200 degrees side to side. Throughout this system is a permanent feedback circuit to return hydraulic fluid to the tank and thus complete the circuit. I've shown a hydraulic specialist my Dynamow with all it's covers removed and he told me that all the components were commonly available. Furthermore, no single component should cost more than £80 to repair or replace and all could probably be sourced on places like ebay for much less.
Is it reliable? I reckon it's pretty bomb proof as I've never heard of a single hydraulic failure on a Dynamow. And I know of only one belt failure (engine to hydraulic pump) in the past couple of years. This belt costs under £10 (from a belt specialist) and is the only belt in the mower.
Front Roller This is a very cheeky design. It's really 4 standard 8 inch lawn mower wheels bolted together by 3 long bolts. Similar sets of 4 have been seen on ebay for £10 plus postage. Just occasionally one of the bolts can break, possibly through the torque the roller transmits, but this is easily replaced for a few pounds by a suitable length of threaded bar from B&Q.
Rear Rollers There are six rollers on a tandem bogie axle which pivots to follow the contours of undulating ground. Three rollers to each axle with different lengths so none has an edge directly behind another edge thus ensuring perfect lawn stripes. The rollers can become seized and damaged as they skid due to lack of cleaning and lubrication. But if damaged all is not lost. Industrial nylon rollers are available cheaply (£1.98 each + delivery and vat) and can be used as a direct replacement. They have the advantage of making cleaning much easier with a hosepipe as water can be jetted through the gaps. They still leave a perfectly striped lawn and I know of one Dynamow with all six original rollers replaced by 28 of these - it works perfectly. Click on the picture below to show how damaged original rollers are replaced by industrials.
These can be ordered online from www.castors-online.co.uk part no. WNY1001244 with 12mm bore size and 100mm diameter. Assemble them well greased ( I use copper grease for it's anti-seize properties) and use 12.5mm (1/2") bore washers to shim them to the correct length on the axle. The headings below will be filled in and expanded as I take photos and have time to write them up. Honda Engine http://www.honda-engines-eu.com/en/images/65892.pdf
Battery Buy two of these 6 volt batteries for £11.99 each + p&p and use the end plates off your old battery to fix them together. Solder on you old battery leads and plug. Cheaper than the £60 to £70 mower dealers demand for exactly the same battery from the same maker. I've got one of these that's 13 years old and still works perfectly - far superior quality to the Japanese/Chinese lead acid batteries.
Bowden Cables Never had to replace one but there are dozens of cable makers who will make a replica if you send them a sample. Motor cycle dealers can also be useful. Let me know if you find a good one and I'll include their details.
Cutting deck and blade I've never dismantled the blade clutch on mine but I have removed the blade to find the following information stamped on the bottom of the clutch assembly. Blade Matic by COMET Richmond Indiana USA Part No 208203 I believe this is their website www.hoffcocomet.com - have a browse and see what you find. If you have no luck sourcing one why not take it to a brake and clutch relining specialist? Nothing hi-tech so shouldn't faze them. The blade clutch adjustment is clearly stated in the handbook.
The cutting blade is from an Italian Harry mower part no. HA 423 40 803. Here is a picture of the blade fitted to a Harry mower if it helps a mower dealer identify it for you.
Sadly Harry is now in receivership but they made tens of thousands of professional quality mowers so blades are plentiful on ebay selling for £15 to £20 plus p&p. Just make sure it's the 22" blade as Harry made mowers in many sizes.
Plastic Fairings Fight among yourselves for these - some of the only unobtainable bits I can think of. The rear side covers are the most likely to be damaged or missing and I've heard of them change hands for silly prices. So save any bits you have and stick them together like a jigsaw. Mine are heavily plated with aluminium sheet at the rear and joined by pop rivets. Then some P38 body filler was smoothed over the joints and the whole thing sanded and sprayed.
The front bumper moulding is usually still present but damaged. Use the same tip as above to restore it. The left hand side of mine was completely missing so I used sheets of cardboard to make a mould and then formed a new section with a Halfords body repair kit.
Grass Box Collector Again now difficult to find though they do appear from time to time on ebay. But don't let the lack of a grass box put you off.
I seldom use mine as I cut the grass more frequently with the Dynamow because it's now a fun job. The cuttings tend to be small and just go back into the lawn, Is this called mulching?
Paint I have found Motorist Discount Centre aerosol "Tetrosyl Colour Match Red Code 20" to be a very good match. But it does depend on how much yours has faded. Cost is £5.29 per can and I found them very helpful.
The disclaimer All the above information is provided in good faith based upon my experience. However it is not to be considered definitive. You should satisfy yourself that it is accurate and only attempt any repair or maintenance you are competent and qualified to carry out. Sorry for that heavy bit but in today's compensation culture I have to protect myself.
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If you have any Dynamow spare parts information or maintenance tips you would like to share please email me |
