Big ride on mower

[aczlan]

you are going to have to help me with the hydraulics bit as l am not clued up on them,
open centre would be where the inlet or pressure port is connected to the outlet and hence tank when the lever is in the middle position ? and does the lever stay in any of the 3 positions forwards,backwards and centre/off ?? every valve l have used has been spring loaded to centre

Correct. For a detailed explication, Wikipedia says it better than I can (emphasis mine):

Open-loop: Pump-inlet and motor-return (via the directional valve) are connected to the hydraulic tank.The term loop applies to feedback; the more correct term is open versus closed "circuit". Open center circuits use pumps which supply a continuous flow. The flow is returned to tank through the control valve's open center; that is, when the control valve is centered, it provides an open return path to tank and the fluid is not pumped to a high pressure. Otherwise, if the control valve is actuated it routes fluid to and from an actuator and tank. The fluid's pressure will rise to meet any resistance, since the pump has a constant output. If the pressure rises too high, fluid returns to tank through a pressure relief valve. Multiple control valves may be stacked in series [1]. This type of circuit can use inexpensive, constant displacement pumps.

Aaron Z

 

[MossflowerWoods]

Looks awesome so far.

#1 - why two seats on a mower? Do you need a Navigator?
#2 - what will you make the body out of?

Thanks for sharing sir!
David

 

[AndyUK]

I am worried that your ground speed will be too fast at the proper speed to for the mower decks run. How close are you too a test drive?

well now is a good time to question it, once l have made my engine mounts it will be a lot harder to change, l could change the layout and drop a suzuki transfer box in the drive train to give a 2 to 1 drop or even 4 to one with aftermarket gears if needed,

l have never been a work it out technically sort of guy more a "lets try it and see what happens" but based on engineering principles, now maths never was my strong point so following may be wrong and l am sure some one will be along to correct me ,

the mower l have the decks from ( jacobson HR-5111 ) l think seems to make max power at 2500 rpm according to this manual l found on line http://isurplus.com.au/manuals/Jacobsen HR-5111 Parts Manual.pdf

it also says the forward cutting speed is up to 8.5 mph, l dont want to run my engine at high rpm's so l am going to assume it will be 2000 rpm when l am cutting ??

if the engine is turning at 2000 rpm and l am in fourth gear which is 1 to 1 then there is 2000 rpm going into the diff ( first diff )
which is 4 to 1 so 2000 divided by 4 would mean that my drive shafts are heading into my axle diffs at 500rpm when the engine is spinning at 2000rpm ?? the axle diffs are 5.125 so the 500rpm gets divide by 5.125 which gives me 97.5 revolutions of the wheel for every 2000 revs of the engine ?

tyres are about 31" tall which equates to 90" circumference, so in a minute they would cover 90x97.5 = 8775 inches divided by 12 to get to feet =731 feet a minute x 60 to get to hours = 43,860 feet per hour as there is 5280 feet in a mile divide by 5280 to get to miles per hour = 8.3 miles per hour in 4th gear at 2000 rpm
now thats in fourth and l have 3 below that 3rd is 1.15 2nd is 1.87 and first is 2.92

l think that works out at
1st= 2.8 mph
2nd=4.4 mph
3rd= 7.2mph
4th= 8.3mph
5th= 9.2mph

all at 2000rpm does that sound right ?? and is 2.8 mph slow enough to mow at ??

 

[AndyUK]

Looks awesome so far.

#1 - why two seats on a mower? Do you need a Navigator?
#2 - what will you make the body out of?

Thanks for sharing sir!
David

thats a seat for my honey, l can show her how it works and leave her to it while l go back in the workshop and build a better one lol

and aluminium for the body panels l think

 

[94BULLITT]

It sounds like your gear will be fine. I just did not want to see you have something that in 1st gear you were running 10mph. For your mower deck gearing you may want to look at the blade tip speed in feet per minute. I would not go lower than 14000fpm. Some zero turns are over 18000fpm.

 

[AndyUK]

It sounds like your gear will be fine. I just did not want to see you have something that in 1st gear you were running 10mph. For your mower deck gearing you may want to look at the blade tip speed in feet per minute. I would not go lower than 14000fpm. Some zero turns are over 18000fpm.

how do you work out blade tip speed ??

dia cutter x pi 24 x 3.142 divide into the speed you want ?

24x3.142=75.4 divided into 18,000 = 240 rpm or about 1/8 engine speed
dose that make sense, dosent seem very fast to turn the blades ??

 

[woodsmith]

If you have the hydraulic pump on the crank, could you run it via an electric clutch from an Air Con compressor? Not sure what the power capacity of one would be though. You could look having it set up like a power steering pump driven from the crank pulley but via the clutch.

hi woodsmith

you can come see me anytime, infact l will be in manchester next week, openshaw where ever that is l havent looked yet,

cheers Andy

Cheers for that, Andy, I will bear that in mind.
Openshaw is at the 3 O'clock position of Manchester, I am at the 9 O'clock side.

thats a seat for my honey, l can show her how it works and leave her to it while l go back in the workshop and build a better one lol

and aluminium for the body panels l think

Ahhh, the honey seat!

That is what messed up my whole trike design!:laughing:

 

[94BULLITT]

how do you work out blade tip speed ??

dia cutter x pi 24 x 3.142 divide into the speed you want ?

24x3.142=75.4 divided into 18,000 = 240 rpm or about 1/8 engine speed
dose that make sense, dosent seem very fast to turn the blades ??

I'm not good at math but here is a link to a forumula I found.

 

[aczlan]

how do you work out blade tip speed ??
dia cutter x pi 24 x 3.142 divide into the speed you want ?
24x3.142=75.4 divided into 18,000 = 240 rpm or about 1/8 engine speed
dose that make sense, dosent seem very fast to turn the blades ??

18000/((24 x 3.142)/12) would be the formula (comes out to 2864 RPMs), the difference is that the circumference of 75.4 is in inches and you have to convert it to feet.

Aaron Z

 

[AndyUK]

18000/((24 x 3.142)/12) would be the formula (comes out to 2864 RPMs), the difference is that the circumference of 75.4 is in inches and you have to convert it to feet.

Aaron Z

thanks Aaron
that makes more sense, l dont know why but l expected the cutter motors to be going at least as fast as the engine

these are the 3 hyd motors of the cutting deck although l might go up to 4 at a later date

now as the pumps are in series l guess l dont need a large pump as the fluid leaves one and goes into the next, where as in parallel l would have to supply them all at the same time, now l have 2 pumps here and can maybe get a 3rd

this is the one l would like to use as l have it and it will be easy to mount, l see its a vickers vane pump but that is all l know, l cant see any arrow indicating the direction it would like to turn

the other pump l have is off a 6 ton excavator, probably 4 times the size of the one above physically, and l might be able to get the one off the mower the cutting decks came from but that is a multiple pump and was mounted flywheel end which suggests it rotates the wrong way