Pitch of the monorail

Maintenance, accessories, operation. Anything to do with making your erg work.
HornetMaX
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Posts: 469
Joined: September 14th, 2021, 5:41 am

Re: Pitch of the monorail

Post by HornetMaX » May 15th, 2024, 4:52 pm

Quick update: got a cheap protractor (6 euros online) but it's sort of useless for various reasons.

Then, only then, I realized my Pixel 4a shows inclination with respect to horizontal when taking a picture: I gave it a try and it seems precise enough for the purpose (i.e. having the rail angle somewhere between 1 and 2 degrees forward with respect to horizontal). So I kind of validated the numbers I see.

I have a spreadsheet where you can input:
  • the measured Hrear and Hfront, the height of the rail (from the floor to the top of the rail) at beginning and end of the rail (where the shiny rail gets covered by plastic bits).
  • the measured L, the rail length between the two points you measured the height at.
  • the measured D, the distance between the mid-point of the rear feet and forward feet
  • the measured H, how much you must raise the front to have the rail perfectly horizontal (easy to find with with a bubble level)
And it will tell Hc, you how much you need to raise the front (or lower the front, i.e. raise the rear) to compensate for your floor slope (if any). It's just basic trigonometry, but if somebody needs it, PM me.

On my RowErg (std legs, so should be the same as a model D):
  • Hrear = 307mm, Hfront = 278mm. These should be the same on all RowErgs std legs and model Ds.
  • L = 1200mm. These should be the same on all RowErgs std legs and model Ds (if you measure where I measure).
  • D = 2245mm. These should be the same on all RowErgs std legs and model Ds, probably also RowErgs tall legs and model Es.
  • H = 70mm. This depends on the slope of your floor. If your floor is horizontal, this will be something like 54mm.
  • Hc = 15.7mm. This depends on the slope of your floor. If your floor is horizontal (H roughly 54mm), this will be 0.0mm.
For the fun: if the rail is pitching forward too much with respect to the nominal value you lift more your body vertically at each stroke. How much depends on the extra slope and on how mush you move the seat during the stroke (I used 480mm for me, I'm only 172cm tall).
If the extra work you do due to that is totally wasted (let's assume, not sure how valid that is) it's possible to compute how much work you have wasted and also how much power.
I took my 72Kg, but only considered 47.5Kg (I've found somewhere each leg is typically 16% of the total body weight, let's say legs are not lifted more due to slope).
The for each one of my PBs (500/1k/2k/5k/10k/HM/FM) the c2 logbook gives the the avg pace and hence avg power, plus I can compute the avg stroke rate and use all these to compute the power I wasted (power I produced that didn't went into the erg) and the potential avg pace (so also the overall time) that I would have done if no wastage had occurred (i.e. if the rail had the correct slope). Here are the numbers:

Code: Select all

	T		Strokes	SR	Pace	P	E_Lost	P_Lost	P_eq	Pace_eq	T_eq
Event	hh:mm:ss.d	[-]	[-/m]	m:ss.d	[W]	[J]	[W]	[W]	m:ss.d	hh:mm:ss.d
500	00:01:36.6	62	38.51	1:36.6	388.27	97.42	1.01	389.28	1:36.5	00:01:36.5
1000	00:03:31.8	121	34.28	1:45.9	294.70	190.12	0.90	295.60	1:45.8	00:03:31.6
2000	00:07:24.2	224	30.26	1:51.1	255.57	351.95	0.79	256.36	1:50.9	00:07:23.7
5000	00:19:21.7	543	28.05	1:56.2	223.25	853.17	0.73	223.98	1:56.0	00:19:20.4
10000	00:39:48.5	1060	26.63	1:59.4	205.49	1665.50	0.70	206.18	1:59.3	00:39:45.8
21097	01:26:04.6	2232	25.93	2:02.4	190.86	3506.97	0.68	191.54	2:02.3	01:25:58.5
42195	03:00:24.1	4482	24.84	2:08.3	165.87	7042.22	0.65	166.52	2:08.1	03:00:10.0
1973, 5'8" (173cm), LW, started rowing Sep 2021 (after 10 years of being a couch potato), c2 log

RowErg PBs: Image

Tsnor
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Joined: November 18th, 2020, 1:21 pm

Re: Pitch of the monorail

Post by Tsnor » May 15th, 2024, 5:09 pm

HornetMaX wrote:
May 10th, 2024, 4:58 pm
...
Now, in order to compensate for my garage slope, I'll likely buy a protractor (something like this: https://www.kstools.com/en/products/han ... 1011737044), try to get anything between 1 and 2 degrees from horizontal and call it a day.
No need. C2JONW said its about an inch difference front to rear for the rail "approximately 1" height difference over 48" of the rail". That's about 1.5 inches difference for the feet. Stick a wood 2x4 (which is actually 1.5 inches by 3.5 inches) under the front feet then level it with your spirit level then remove the piece of wood.

HornetMaX
2k Poster
Posts: 469
Joined: September 14th, 2021, 5:41 am

Re: Pitch of the monorail

Post by HornetMaX » May 15th, 2024, 6:00 pm

Tsnor wrote:
May 15th, 2024, 5:09 pm
HornetMaX wrote:
May 10th, 2024, 4:58 pm
...
Now, in order to compensate for my garage slope, I'll likely buy a protractor (something like this: https://www.kstools.com/en/products/han ... 1011737044), try to get anything between 1 and 2 degrees from horizontal and call it a day.
No need. C2JONW said its about an inch difference front to rear for the rail "approximately 1" height difference over 48" of the rail". That's about 1.5 inches difference for the feet. Stick a wood 2x4 (which is actually 1.5 inches by 3.5 inches) under the front feet then level it with your spirit level then remove the piece of wood.
Yeah, that's doable too. I just find the maths more reassuring but that's me :)
In the end, only stuff needed is a ruler and a spirit level anyway.

BTW, for me the difference front-rear of the rail is like 29mm (1.14") over 1200mm (47.24), so the difference for the feet is more 54mm (2.13").
So I'd advise to measure that anyway and then proceed as you said (or as I described, whatever should work).
1973, 5'8" (173cm), LW, started rowing Sep 2021 (after 10 years of being a couch potato), c2 log

RowErg PBs: Image

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