cricket bowling machine / baseball ?

[mikhailfaradayski]

Nope, it was BAS who mentioned the insurance bit.

Have another look at the question and answer,
do you know the difference between diameter and circumference?

 

[DrGonzo]

Nope, it was BAS who mentioned the insurance bit.

Have another look at the question and answer,
do you know the difference between diameter and circumference?

"read the question" - oops, missed it.
multiply that by 3.14
circumference is not 100mm but 314mm ish or 0.314m
So,
70mph = 112kmh
112kmh = 112000metres/h = 1866.66metres/min
Diameter = 0.1m
Circumference = 0.314m
RPM = 1866/0.314 = 5942PM

I thought 18k was sounding v high

 

[mikhailfaradayski]

now you have established how to calculate your required RPM.

Its still in a basic form, maybe factoring in a slip of 15% isn't unreasonable.

The link you gave to ebay. That thing has no 'spinny-roundy-bit', its just a solenoid.

Do you not have a SCRAP YARD anywhere near you?
When i was a student, i often spent a hung over, but happy sunday morning in one trying to cheap bits for a mk11 escort.

 

[DrGonzo]

now you have established how to calculate your required RPM.

Its still in a basic form, maybe factoring in a slip of 15% isn't unreasonable.

The link you gave to ebay. That thing has no 'spinny-roundy-bit', its just a solenoid.

Do you not have a SCRAP YARD anywhere near you?
When i was a student, i often spent a hung over, but happy sunday morning in one trying to cheap bits for a mk11 escort.

Aha, it's just the bit on the side of the actual starter motor?
Yeah, there must be a yard somewhere, ideally finding 2 identical motors would be good for 2 independent wheels.

 

[ban-all-sheds]

Can you give the answer to this question?
By all means, describe the formula, but can you tell me the answer?

What is the required rpm to give a peripheral speed of 70MPH assuming there are no frictional losses in the system?

The drive wheel diameter is 100mm

Assuming 1:1 gearing.
70mph = 112kmh
112kmh = 112000metres/h = 1866.66metres/min
Circumference = 0.1m
RPM = 18,666RPM

Try again.

 

[ColJack]

he did, try to keep up BAS...

 

[ban-all-sheds]

That's what comes of starting a reply and then wandering off to do something else...

 

[ColJack]

so you managed to type "Try" and then had to go and think about the next word for 47 mins???

 

[LiamPope]

so you managed to type "Try" and then had to go and think about the next word for 47 mins???

Ha haa

This reminds me of my A-level design tech project. I made a table tennis server following similar principles. Well, a rapid fire gun if I'm totally honest, but it could potentially have been put near a table tennis table and could motor up and down to either shoot straight over the net or bounce first for a serve. Mostly I just shot balls around the workshop, and was even asked to do this on a 'send your kids to our school' type of open evening . I like to think enrollment that year was particularly healthy.

Anyway - the theory is all good. Mine just used RC car wheels with foam tyres and small 12V motors, but of course you will need much more power to accelerate cricket balls! Car starter motors might be a good bet, but decent mains power tool motors may be easier to bend to your wicked desires, and will commonly come with a speed controller already attached. You need a pretty good speed differential between the wheels to achieve good spin if you think about it, and if you want your launch velocity to stay high, you have to speed up one wheel as much as you slow down the other - so add maybe even 50% to your desired max rpm to allow this.

Best of luck - you should at least get an interesting ****ed up BBQ toy to impress your mates with.

Liam

 

[ban-all-sheds]

so you managed to type "Try" and then had to go and think about the next word for 47 mins???

No - I sorted out the quote I wanted, typed both words, clicked Preview to proof-read it, and then got side tracked.

Came back later and just hit "Submit"....

 

[DrGonzo]

so you managed to type "Try" and then had to go and think about the next word for 47 mins???

Ha haa

This reminds me of my A-level design tech project. I made a table tennis server following similar principles. Well, a rapid fire gun if I'm totally honest, but it could potentially have been put near a table tennis table and could motor up and down to either shoot straight over the net or bounce first for a serve. Mostly I just shot balls around the workshop, and was even asked to do this on a 'send your kids to our school' type of open evening . I like to think enrollment that year was particularly healthy.

Anyway - the theory is all good. Mine just used RC car wheels with foam tyres and small 12V motors, but of course you will need much more power to accelerate cricket balls! Car starter motors might be a good bet, but decent mains power tool motors may be easier to bend to your wicked desires, and will commonly come with a speed controller already attached. You need a pretty good speed differential between the wheels to achieve good spin if you think about it, and if you want your launch velocity to stay high, you have to speed up one wheel as much as you slow down the other - so add maybe even 50% to your desired max rpm to allow this.

Best of luck - you should at least get an interesting p****d up BBQ toy to impress your mates with.

Liam

eg: Motors
rubber wheel
More industrial rubber wheel

some type of waste pipe for the feeder, which could maybe be cutout to allow the wheels to spin in it, this would keep the ball running in a straight line on exit and also provide the feeder mechanism.

I'm sure I can get cheaper.
How would you alter the speed if they didn't come with a speed controller - alter the current? Have to go back to my physics days...

wheels probably have to be 30cm in diameter.
70mph = 112kmh
112kmh = 112000metres/h = 1866.66metres/min
Diameter = 0.3m
Circumference = 0.942m
RPM = 1866/0.942 = 1980PM
+ a nominal 50%
say 3,000 RPM
+15% loss
3,500RPM[/url]