Saturday, 28 November 2020

Turfenomics: Productivity Part 4 Mower Efficiency and How to Cut Your Cost of Mowing in Half

How much grass can your mower cut? The most basic way of calculating this is to take the width of the mower and multiply it by the speed. Let's say our mower is 2 meters wide and can mow at 10 km/h (keeping the match simple here). In one hour it will have cut 20,000 square meters or 2 ha. Wow, that's a lot of grass. Unfortunately it's not that simple. A lot of things go into how much grass you can cut and any observant turf manager will know that the actual productivity of a mower will be much lower than the maximum theoretical productivity as calculated above. This post will discuss what influences mower productivity and strategies we can use to maximize how much grass we can cut with a given mower or resource input.

So why isn't our actual mower productivity the same as the maximum theoretical productivity? A lot of "mowing" isn't actually mowing. We use an hour meter to calculate how many hours the mower is operational and during this operational period the mower is doing things like warming the engine up at the start of the day, driving to the area to be cut, turning the mower, waiting for golfers, returning to the shop, and cooling the machine down before you turn the engine off. All of these mentioned things are time on the hour meter that are not cutting grass! Over the last few years of closely measuring mower productivity I have found that you will probably get anywhere from 10% (tees) to 40% (fairways) of the maximum theoretical productivity of a given mower. That means that you are only actually cutting grass 10-40% of the time that a mower is operational. What a waste!

Mower efficiency

There are also things that impact productivity while cutting grass. Things like how fast the mower is set to mow, mower overlap between passes,  and obstacles that cause the mower to have to reduce speed or turn to avoid. At my previous course we have very bumpy fairways and it took twice as long to cut 1ha as it does at my new course which has much smoother fairways.

A lot of what superintendents talk about is mower routing to increase efficiency. This is making sure that the mower isn't backtracking or transporting for longer than necessary distances. This is a great place to start but in the grand scheme of things isn't a major factor in mower productivity from what I have seen. Obviously this needs to be taken into account and mowers shouldn't be driving back and forth between holes over long distances. A classic example of this strategy going wrong was at my last course the operator would avoid golfers at all costs to avoid having to wait or disturb their round of golf. The result was a substantial amount of time spent driving from hole to hole to avoid golfers. It was much more productive to just stick to the hole that you were on before going to another hole.

Mowing pattern also has a huge impact on productivity because some mowing patterns require more mower turning which impacts productivity. The more turns that are required the more time will be spent not mowing on a given area. Let's look at my first fairway. It's a 510 yard par 5 with a long narrow fairway. The fairway portion of the hole is 375 meters long and the fairway averages about 30 meters wide. I'm using meters here because my mower productivity is measured in meters and ha.

Lets again take our 2 meter wide mower. This mower is sort of small for fairways but it's easy for math. The first fairway is almost 1 ha exactly. With our 2 meter wide mower going 10km/hr we will spend about half an hour mowing this fairway assuming no turns or waiting for golfers and we are able the mow flat out without slowing. Unfortunately we have to turn the mower because our mower isn't the perfect width of the fairway and we will have to do multiple passes to cut the fairway. Every time the mower has to make a 180 degree turn while striping it adds 8 seconds to the mowing time of the fairway. The worst case scenario for mower turns would be mowing the fairway side to side at 90 degrees to the line of play. At 375 meters long with a 2 meter wide mower that gives us 188 turns assuming no overlap. 188 turns multiplied by 8 seconds per turn gives us 1504 seconds or 25 minutes spent turning for a total mow time of 55 minutes. The other extreme is to mow the fairway lengthwise. At 30 meters wide we need to do 15 passes assuming no overlap. This will take us 120 seconds or 2 minutes to turn the mower (assuming stripes) for a total mow time of 32 minutes. In this case, mowing direction can influence our productivity by 42% or more! We can spend almost double the amount of time cutting a given area. Of course there are reasons that might justify this added expense but it's worth knowing what decisions like mowing pattern have on productivity. 

The real world these inefficiencies are even worse because of overlap. Let's say we have 20cm of overlap (10% of mower width) per pass. 20 cm x 15 passes is 300 cm or 3 meters. This adds 1.5 more passes to the job or a total job time of 32.2 minutes cutting lengthwise. Cutting from side to side we now have to make 208 turns which takes us 58 minutes to cut the entire fairway. This leaves us with an productivity loss of 55%! Over half as much grass cut per hour! It get's worse because with these mowing patterns you also have to do a cleanup pass around the perimeter of the cutting area! You are now cutting this area twice where this area is simply included in the regular mowing of the hole on half and half mowing. Of course we probably won't cut this way every time and if you do striping the productivity loss will probably be somewhere between the two mowing patterns.

If you cut half and half patterns you might not have to stop mowing to turn the mower. You can do wide turns while mowing grass at a slightly slower speed but you will still be cutting grass. This is where you will achieve the maximum actual productivity when it comes to mowing patterns. Actually, this isn't quite true. The maximum mowing efficiency comes if you never turn the mower like they do at Augusta National. The only catch is you need 22 $80,000 fairway mowers to pull it off. So the next time someone says Augusta isn't efficient I would disagree. They mow the fairways in the most efficient manner possible!

Ok cool. We all know mowing pattern impacts productivity but what about disruptions like waiting for golfers? Everyone knows this impacts productivity but it's hard to actually test it out. This spring I had an amazing opportunity to test this out as we were closed to golfers for an entire month in April due to Covid19. I had productivity data before the closure and productivity data during the closure.

Before the closure we were getting about 0.9 ha/hr on our fairway mowers. During the closure this jumped to 1.5 ha/hr even with a rooking operator (our GM). Once we opened back up this dropped down to 1.3 ha/hr. With golfers our average productivity was 1.1 ha and without it was 1.5 ha/hr. This is an increase of 27%. I've heard the 30% figure thrown around often and I was able to measure this in reality. The productivity gain was more in other areas such as tees and greens as we removed obstructions like flags and tee markers. On tees productivity jumped 200% because half the time spent "cutting" tees is spent moving markers. 

I don't know about you, but a 30% increase in productivity is massive. Combine this with the mowing pattern efficiency gains and you might be able to cut twice as much grass per hour. Double you productivity! Again, this is exactly what we did. After we opened back up we doubled the amount of grass we were able to cut or halved the amount of labor or equipment we needed to get the grass cut efficiently. Mowing is our most expensive maintenance practice so we stand to save the most if we can find ways to reduce the amount of mowing that is required.

How did we do this even when golfers returned? We prioritized productivity over all else. We cut as much grass as possible with the biggest and fastest mowers. This meant our fairway mower would now also cut approaches, some collars and some of the big tee boxes. Our big rough mower cut all the rough, and our small rough mower was no longer needed. There was no change on greens other than restricting start times and starting earlier to ensure that golfers would never catch our greens mower. 

We also avoided golfers at all cost with fairways and rough. We were easily able to cut half the fairways ahead of the golfers each morning. 9 holes takes us about 5 hours (total job time not just mow time). We start mowing at 5 am and the first group was off at 7 am. The first groups golfed pretty quick in about 3 hours. This had them finishing their round around 10 am or exactly when we were finishing mowing the 9 holes. The fairway mower was cutting every day without any golfer interference. Any time we were able to cut quicker, we would add more work to the fairway mowing job to ensure that it would be out mowing grass at a high productivity (it's our most productive mower) level for the most amount of time each day. This meant that we made some fairways bigger and cut more areas with the fairway mower as previously mentioned.

We had to change the mower routing to make this work because we used to mow fairways in blocks. One day we would cut the front nine and the other day we would cut the back nine. This practice maximized routing efficiency but sacrificed mower productivity in a big way. If we mowed fairways this way and started at 5 am, golfers would catch us about 70% of the way through the front nine days resulting in us having to mow the last 30% at potentially a 50% loss which would add about 15-20% to our total mow time and disrupt the golfers. This was made slightly worse because we would have to wait more often with our half and half mowing pattern as we would come across golfers on the green, tee and fairway that we would potentially have to wait for. To avoid this we could stripe but this would result in an inconsistent look and add time spent turning. Instead we would skip holes and cut half of the area each day. Notice I didn't say we would cut half of the holes each day. As each hole is a different size, we broke the mowing days down by area instead of hole numbers to evenly spread the work. With a slightly less efficient mower routing we were able to mow at maximum productivity all the time.

Rough was a bit trickier. We have more rough than we can cut in 2 days. We could have cut rough over 3 days but we didn't have the staff to pull this off. Instead we broke down the rough area on each hole and allowed a proportional amount of time for each hole to be cut at maximum productivity. This means that we would leave a hole without cutting all the rough on it! Instead of getting 2 or 3 hours of high productivity mowing on rough each day we now got 5 hours every day. This allowed us to get almost all the grass inside the cart path or close to the centerline of the hole. We would then go back and get the other stuff during golfer play. While it was slightly less productive, we were waiting less because these areas were far from the centerline and we could mow without stopping even when golfers were present. This allowed us to cut twice as much grass with a single mower and operator than we did in the past. We actually cut more grass than in previous years but with half the machine time and labor. A savings of over 600 hours on each.

Below is the tool I developed to help rough mower operators know how much time they had per hole. 

Now you'll notice that a tool like this doesn't maximize production (total amount of grass we can cut) directly. It indirectly maximizes production by keeping the mowers working in an environment that allows for maximum productivity without setting any production goals. Cut as much grass as you can in this amount of time. This reduces pressure on mower operators tremendously.

I also use a similar tool for when I do my favorite morning routing of rolling all greens, changing all holes and raking all bunkers. While I could simply brute force this job the most important thing is to get the greens rolled and the holes changed ahead of the first group of golfers. Raking bunkers is secondary and this allows me some flexibility to address factors that can influence my productivity like bad weather and working while wearing rain gear. While I can easily do this job before the 6 hour deadline when conditions are perfect, if the conditions are bad I cannot, so I need a way of gauging my progress and adjusting on the fly. We can always go back for the bunkers I miss or get anyone else who has an opportunity to help make up for my loss of productivity with lower productivity loss while golfers are on the course.

By assigning a time limit on each hole I can easily gauge my progress and adjust as I go. If we have 18 holes and 6 hours that leaves me 20 minutes per hole to drive there, roll the green, change the hole and rake as many bunkers as I can. Easy.

If we instead set a production goal instead of a productivity goal I would fail every time something negatively affected my productivity. Golfers would catch up to me on hole 15, I would be rushing and they would have to golf their last 3 holes on dewy, unrolled greens on yesterdays worn out pin locations.

I hesitate to post something like this because it can give a course a huge competitive advantage. Luckily for me no one reads this blog and people are too stuck in their ways to change. Joking aside, the lessons I learned this year will have a huge impact on the cost of our operations going forward and I hope they can help you too.

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