Your browser is no longer supported

For the best possible experience using our website we recommend you upgrade to the newest version of your browser.

Your browser appears to have cookies disabled. For the best experience of Construction News, please enable cookies in your browser.

Welcome to the Construction News site. As we have relaunched, you will have to sign in once now and agree for us to use cookies, so you won't need to log in each time you visit our site.
Learn more

The leaner, fitter Kubota mini excavator cuts a dash

SMALL PLANT & TOOL HIRE

Kubota introduced its Dash 3 mini excavator range in a bid to regain the market-leading position it used to hold in the UK. Geoff Ashcroft and John Woodward compare the KX71-3 against its predecessor

FACING stiff challenges from the likes of Takeuchi, JCB and Volvo in the mini excavator sector, Japanese maker Kubota has revisited the drawing board to engineer its latest 2.8-tonner, the KX71-3.

To improve its appeal, the firm took a clean-sheet approach with three objectives: lower operating weight, reduce tailswing and improve hydraulic performance.

'The original KX71 ballooned to almost 3.1 tonnes in its final form, ' says Kubota (UK) sales and marketing manager Richard Harrison.'It needed to go on a diet while having its performance and stability improved.'

While the physical size of the machine remains similar to the outgoing model, it tips the scales at just 2,685 kg with a canopy and 2,800 kg with cab and long arm. It is a machine that is virtually new from the ground up.

Just the four-cylinder V1505 engine is carried over.

In the transition to Dash 3 guise, the mini excavator has lost its angular and, some would say, old-fashioned appearance, in favour of rounded panels and smoother, cleaner lines.

'We've tried to combine the necessary improvements in a package that is much more aesthetically pleasing to look at, ' says Mr Harrison.'But it also has to be practical, productive and comfortable to use.'

'To help with stability, we made the undercarriage 5 per cent longer and switched to an X-frame instead of a parallel beam system. By doing so, we have put strength in and improved corner-to-corner stability.'

Bottom rollers are now in a twin-roller design and straddle the central track guide and the rubber tracks now conceal a staggered metal bar construction that runs the full width of the track. Kubota says the changes have led to quieter running and greater track strength.

A 3 per cent increase in track motor effort, combined with an increase in travel speed from 4 to 4.6 km/h complete the undercarriage revisions.

Cast iron tipping links on the bucket geometry - also pinned and bushed - increase serviceability of the machine, while lift capacity, breakout capacity and digging depth have also been improved.

Those opting for a cab - Kubota believes most KX71-3 sales will be for cabbed variants in the UK market - get a new environment in which to work.The former TOPS (topple over) structure has been replaced by a ROPS/FOPS cab, which uses flat glass panes secured using push-fit rubber surrounds.

'We wanted to reduce some of the glass replacement cost owners face from vandalism, ' says Mr Harrison.'Curved windows look nice, but they're too expensive.'

Inside the cab, the operator is greeted with short-stroke joysticks and wrist rests, although the quality of finish on the wrist rest brackets leaves a lot to be desired, as the bolt-together brackets have sharp, square corners.

Looking for greater operating efficiency, the firm has moved away from a gear pump hydraulic system.Two variable displacement pumps on the KX71-3 now offer up to 32.2 litres/min, with constantly adjusted flow and pressure according to demand.

'Variable output allows us to cut back on fuel use and improve operating efficiency, ' says Mr Harrison.'The pumps only supply oil on demand, so we're not wasting energy and creating excessive heat by pumping oil around the system unnecessarily.'

It also means the engine doesn't work as hard as it would when coupled to a gear pump system, which could lead to improved operating efficiency, lower noise and lower fuel consumption.

'The V1505-EBH engine has lower emissions and produces 27.5 hp at 2,300 rpm instead of the Dash 2's 30.1 hp at 2,600 rpm, ' he says.

Engine access does not seem to have been hindered by the reduced tail swing of the KX71-3. Its rear-end projection has been shaved back to 1,200 mm from 1,375 mm, with counterweight protection on the corners now provided by cast iron guarding.

The firm could have taken the easy way out by making small changes to the existing model - the KX71-2 came to the UK in 1996, and was soon followed by the Alpha series, which offered a few tweaks and adjustments to make the machine user-friendlier.

But far from it.To capture a bigger slice of the UK market, the Japanese firm realised the KX series needed to distance itself from the competition by a sizeable margin in order to entice hire fleets and owner-operators. It made its intentions clear since, for all the improvements on offer, the price remained unchanged.

Kubota ZX71-3

Machine weight: 2,685-2,800 kg

Engine: 27.5 hp Kubota V1505-EBH four-cylinder

Boom: 2.1 m one-piece boom

Boom offset: 80 degrees left, 60 degrees right

Dipper options: 1.15 m, 1.35 m

Standard bucket: 0.07 cu m

Track options: 300 mm rubber shoes

Track drive: Two-speed hydrostatic - 0-2.7 and 0-4.6 km/h

Operating modes: None

View from the cab

BYJOHN WOODWARD

FOR 20 years I considered Kubota to offer the best quality, performance and value for money of any of the mini excavator manufacturers available in the UK. But at the time the Japanese manufacturer was paying my salary.

Four years after leaving the firm I was interested to see whether a more objective view of the product would confirm that earlier enthusiasm.

I was very familiar with the predecessor, the KX71-2. In its day it was the market leader in the 2.5 to 3-tonne sector and was favoured by many plant hirers. It was just possible to tow the machine on a trailer, yet big enough to pass itself off as a 3tonner and perhaps command a slightly better hire rate.

Over the years, Kubota maintained market leadership but the excavator put on a bit of weight.The interim KX71-2 Alpha model had increased to just short of 3 tonnes and it was difficult to see how the product and the performance could be improved while favourably reducing its weight.As a result, the competitors stole the initiative.

It would appear that Kubota engineers went right back to the drawing board in designing the KX71-3, as the only thing to remain from the old model's structure is the V1505 engine.

The KX71-3 is a short-radius machine but gets its stability by the use of a long undercarriage, which includes a revised bottom roller layout to improve over-the-side stability and a much larger counterweight.

Inevitably, with any short-radius machine there has to be some compromise and the first thing you notice as you enter the cab is the door's width. It is two inches narrower than the KX712, which doesn't sound much but amounts to an 8 per cent reduction and is quite difficult for a big person to negotiate in site gear.

Once inside, the cab is longer and better laid-out - careful positioning of instruments and controls gives a feeling of spaciousness and, despite the meaty corner posts on the new ROPS/FOPS cab structure, the all-round vision is good.

I was pleased to see that Kubota has at last dropped the seatmounted armrests in favour of wrist rests.This, coupled with the revised short-travel servo controls, made the KX71-3 a joy to operate.

Other favourable detailed improvements include the gas strut-assisted front screen and floor pedals for boom offset and auxiliary hydraulics that doubled as footrests when not being used.

Another first for Kubota is the use of a small microprocessor in place of instruments to display fuel level, engine temperature, hours and engine speed. It can be interrogated to provide information about the next service and it records faults to help service engineers.

Maybe this is a tentative step towards making machines more secure.We were told the machine serial number and engine number are also embedded in the processor.

We set out to establish whether Kubota's improvements are worthwhile by comparing the performance with a KX71-2.The latter had 1,600 hours on the clock but was in good condition. It was easy to recall why the KX71-2 was such a popular excavator.

It was fast, controllable and powerful, handling the stiff Northamptonshire clay with ease. Indeed it was difficult to envisage a machine that could put up a better performance.

But the KX71-3 proved a revelation. It easily outperformed the KX71-2, although it was difficult to ascertain which single feature was making the difference.

I believe it had to be the whole package of longer tracks, variable flow hydraulics, improved breakout forces and the smoothness of the controls.

Dozing performance too was excellent with plenty of traction.

A nicely contoured blade allowed material to roll up, tumbling forward instead of falling over the back edge of the blade.

A revised design of short pitch, asymmetric links on the tracks meant the excavator was extremely quiet and smooth in operation without any of the vibration so common on earlier track designs.

The two-speed track control has been moved from the floor to the blade control lever and is much easier to use, with a useful single bleep to tell when you have selected first speed and two bleeps when you select second speed.

Servicing revolves around engine oil and filter changes at 250hour intervals but greasing is still a 10-hour chore and it really is time that manufacturers incorporated sealed pins and bushings for all except bucket linkage.

I was surprised to learn that, despite Kubota being high on most plant thieves' shopping list, the Japanese maker had not yet incorporated any significant measures to make the machine much more secure.

A universal key still gives access to the cab, inspection covers and starts the engine.There is no immobiliser and no track locking plate on the undercarriage.

So is Kubota and the KX71 series as good as I remembered?

Was my enthusiasm justified? And is the latest Kubota Dash 3 an improvement on the previous model? Yes, on all three counts.

Production testing

CONSTRUCTION News went to D Wootton's Spella Works, Lower Boddington, Northants, used by Kubota for machine testing and demonstration purposes.

All measuring and recording equipment was supplied and supervised by Construction News.Output figures were based on a 60-minute hour.The wet Northants clay had a swell factor of 25 per cent and a density of 2,076 kg per bank cu m.

The plant testers would like to thank Richard Sayers and Richard Harrison of Kubota (UK) for their help during this test.

Trenching test

Test method: Equipped with a 600 mm-wide, 0.07 cum capacity bucket. We set both mini excavators on trenching work to pull a 1m-deep trench to the width of the bucket.The test was carried out over 20 minutes with the machines set at full throttle.All earth was discharged alongside the trench.

Spot work rate - KX71-3

Trench length: 12.5 m

Volume of material excavated: 7.5 bank cu m, 9.38 loose cu m

Weight of material excavated: 15.57 tonnes

Fuel use: 1.65 litres

The hourly rate - KX71-3:

Output potential: 37.04 m trench, 46.13 tonnes excavated

Fuel use: 4.89 litres

Weight excavated per litre of fuel used: 9.44 tonnes

Spot work rate - KX71-2:

Trench length: 9 m

Volume of material excavated: 5.4 bank cu m, 6.75 loose cu m

Weight of material excavated: 11.21 tonnes

Fuel use: 1.85 litres

The hourly rate - KX71-2

Output potential: 27.65 m trench, 34.43 tonnes excavated

Fuel use: 5.68 litres

Weight excavated per litre of fuel used: 6.06 tonnes