OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Reel Lawn Mowers, Atco & Villiers etc. Drive reel and cutter reel speed

I am in the process of ggetting an Alroh 17BDB up and running properly. The first test run went ok but the mower speed was a lot higher than I thought if should be. I reLly had to move to keep up even with a lower engine speed and tbe clutch just driving.

All the pulleys look original so I assume it is running at the designed speed. Does anyone hVe an idea of what the normal or average speed should be for the drive reel and cutter reels. Once I confirm a normal kind of speed I can check the Alroh ratios and decide on whether to change any of the pulleys.

Here is a pic of the engine pulleys.

Some cylinder mowers are deliberately designed to have the drum drive clutch slipping all the time, so you can control the speed along the ground by adjusting the clutch. The Scott Bonnar 45 is of this type: you would rarely operate it with the clutch fully engaged. However mowers that use a V belt as a clutch, seldom work this way: it would wear out the V belt.

Alroh is a very competent manufacturer, and is located close to you, so I suggest the first thing you should do is ask their service department whether the drum clutch is intended to slip during normal operation.

I had already checked the parts list I got from Alroh last week but all it contained was a part number. As suggested I then gave them a call. The description for the pulley being 2x1Ax1/2 (I think) suggested a 2 inch pulley. A quick stop at Alroh on the way home to look at the part showed it was a 63mm pulley. I measured the current one when I got home and reckon it is 3". Now I just need to decide 2" or 2.5" as the replacement. They also advised some slip was ok but you would run without slip most of the time.

I checked a 2" pulley on the way home and it is too small (its what they use on the belt drive edgers). 2.5" it will be (as per the factory part).

The reduction from 75 mm to 63 mm will slow it down by 16%, which should be a quite noticeable difference. If it is still too fast for comfort and safety, just switch to the 50 mm one which will give you an additional 20% reduction in speed. There should be no difficulty in getting the outcome you want, and you will continue to have the choices available if you change your preference later. The belt drive is very convenient in that respect.

Hi to Diablo and grumpy,
When cylinder mowers are designed and manufactured, the factors that come into play are number of blades in the cylinder reel, giving X amount of cuts per metre and ground speed at a given RPM.
For example, the 20" SB Model 45 series 1 has an 8 blade cutter giving 95 cuts per yard and a ground speed of 2.75MPH at 2000 RPM.

My question is, if you change the ground speed considerably, will the standard of cut be affected?

Deejay, by changing the ratio of the primary drive from the engine to the reel, without changing the ratio of the reel-to-drum drive, you retain exactly the same cutting geometry including cuts per metre. All that changes is the ground speed. Of course this is adjusted continually by the operator of an SB45, by varying the drum clutch engagement with the squeeze-handle. The Alroh apparently has a fixed in-or-out drum clutch, so the only way to fine-tune the ground speed is by changing the engine speed, or the ratio of the belt drive by replacing the crankshaft pulley. Diablo's machine seems to have had an oversized crankshaft pulley fitted: perhaps the previous tenant was a marathon runner in continuous training.

Thank you Deejay and Grumpy for your input. I had already factored in what you said about the matching change in drive/cut speed ratio Grumpy. I saw that as a positive and it now allows me to select a ratio for the favoured drive speed while knowing the cut will not suffer.
I reckon the previous owner was a marathon runner as you say. One that worked as a greenskeeper at the WACA.

That explains it Diablo - I think working as a greenskeeper at a full sized sports ground would make good marathon training. Incidentally all this means there is a very good chance the machine has been well-maintained since new.

Hi grumpy, and thanks for that...as I don't know the sprocket and chain set-up for the cylinder reel and rear roller, I wondered if that would be an issue.

Having finished another project I finally had time to get back to this one. A 2"pulley was fitted last night. I don't know how it goes yet because 9:30pm seemed a bit late to fire it up for a test run. I will use my gps data logger (normally used for gps speed windsurfing) to get a true speed measurement.

Hi Diablo,
I am looking forward to hearing the results of your test run mate....It would be nice to see it run with a nice and steady walking pace.

Hi Deejay,
A quick test run has been done and I am happy to report that the mower achieved a max speed of 2.5kts.
The downside of using my windsurfing gps data logger is the readout is in knots - and 2.5kts is certainly a long way short of my windsurfing personal best of 34kts.
With a 1:1.852 conversion ratio this is about 4.6kmh . I found this to be a very comfortable walking pace, maybe even a little too comfortable for me.
I will do a better test run when I have more time and will pay closer attention to engine speed. I am not sure of the actual engine speed when the max drive speed was achieved but I reckon it was closer to 3000rpm than 2000rpm.

Hi Diablo,
I am not sure at what the optimum ground speed for your machine is, nor what RPM the Briggs is comfortable with for average lawn mowing.....with my Scotty, my Honda runs at full throttle (governed of course) and combined with the hair-triggered clutch, I can vary the ground speed to my liking. With your set-up however, it seems the PTO pulley diameter is all important.

Your machine had a 3" pulley fitted and was to fast, the 2.5 may be a trifle slow....maybe a 2.75" may be the answer...and you could consequently reduce the engine RPM accordingly to achieve the ground speed you are comfortable with.
Thanks for posting your test results.

Diablo, you said you have used a 2" pulley, compared with the 2.5" which is standard and the 2.75" it had when you bought it. You reported a ground speed of 4.6 km/h, or 2.9 mph. For what it is worth, the average "standard" walking speed for unencumbered male humans is said to be 3 mph, and some crude measurements I have made support this for sustained walking (say, at least half an hour without stopping). However on short walks it may be a bit higher. A lawnmower is a slightly different situation because sometimes you have to engage in tricky steering, which requires a lower speed. Hence my wild guess is that you may have a rather practical general-purpose speed there, but if you were mowing an oval you'd want more, because it is all straight runs and you would end up using it as a physical training exercise to stave off the boredom. (Hence your WACA groundsman's 2.75" pulley, which probably gave him a ground speed of 3.9 mph.)

Getting away from this subjective stuff to something more meaningful, the small horizontal crankshaft side valve Briggs engines like yours are normally governed to 3,600 rpm maximum. The vertical crankshaft ones are traditionally (well, since 1980 anyway - it was higher before that) 3,000 rpm because of blade speed regulations in the US.

Hi Grumpy, the reason I suggested the 2.75" pulley was Diablo's quote above, if he had originally a 3" and found the 2.5" a trifle slow, I suggested that a 2.75" may be the answer.

So the WACA groundsman was cantering along at 6.9 km/h all day.

To mow a garden with some turns and curves involved, I'd be happy with the 4.6 km/h, though it would get boring on long straight runs. What would really suit me is a variable ratio drive, or a slippable clutch like on an SB45.

Got home with enough light and time to mow the back lawn (say 300m2). First impression is that the speed is good on the straight runs and I just need to work on my technique for the turns and the other tight stuff like around the swing set.
Other adjustments needed are - increase the height of the handle as I was stooping a little to hold it and the reel/blade setup so the cut is even.
I also realised just how uneven the back lawn is.

Don't feel badly about the unevenness Diablo. I use a rotary, and every time I mow the back yard it takes me back to the days of my youth driving on bush tracks in an old Land Rover. Even bent the seat back where it rests against the bulkhead.

Don't forget you can use the speed control on the handle to drop to 2,000 or 2,200 rpm when you need to negotiate a bend or steer around an obstacle. Also, with my ancient ATCO 12/49 I used to lift the rear roller a bit when things got really difficult.

Hi again Diablo,
Once you make the adjustments you have mentioned with the handle, you can make the reel to bedknife adjustments....the thread HERE may help you, even though it is for a Scotty; the general procedure would be similar for the Alroh.

Just one question, has the cylinder reel and bedknife been recently sharpened?