| Author |
Message |
Paul Davies (Pwd)
Member
Username: Pwd
Post Number: 1
Registered: 1-2010
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| Posted on Thursday, January 14, 2010 - 3:19 pm: |
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Hi I am building a motorised carriage that is designed to carry a 1/2 kilo weight across rough terrain like a grass field at a fair lick hopefully ..need to go at least 15 mph but does not need to steer ..basicly it just takes off and keep going till it hits something it cant pass
I have built this (see Pic ) out of the Tam twin motor g/boxes but its a bit to low slung and underpowerd so I was hopeing to use a MFA geard motor of 21watts driving a 6mm axle with the spiked tyres on it in a 2 wheel rear drive format then having basic undriven front wheels ..what ratio motor would you recomend assuming the axle bevel gears will be the 6mm bore white ones in 1-1 ratio and do you think it would be feasible..power is 12 volts total weight would be around 1.5 kilos constructed  |
Admin (Admin)
Board Administrator
Username: Admin
Post Number: 1184
Registered: 10-2004
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| Posted on Saturday, January 16, 2010 - 10:41 am: |
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Paul,
The Tamiya set up you have is certainly under powered to meet your criteria. The MFA 919D series will be fine, you will possibly get away with a single motor but two will be more than ample. Use our robot speed calculator to determine the ideal wheel diameter / motor ratio but as you require ground clearance, use large diameter wheels.
If I was making this, I would use 101mm wheels 4608-019 with motor 1450-052 which would give 17 mph. You then need to drive the axle, as you require two wheel drive, you will not be able to direct drive the wheels. Therefore you need your bevel gears idea but that requires precision and no flexing in the chassis. You are better using an indirect drive using a belt or chain drive.
Hope that helps |
Paul Davies (Pwd)
Member
Username: Pwd
Post Number: 2
Registered: 1-2010
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| Posted on Sunday, January 17, 2010 - 12:49 pm: |
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Hi Admin Thanks for the helpfull and informative answer . Just a few more questions ..a do you sell any sort of axle system even in parts form that would make the job of powering the rear wheels any easier..and at one point because I have not enough width to put them end to end to drive the rear wheels I was thinking of driving the front left and rear right wheel with motors directly then fitting an undriven stub axle to the front right and rear left..would this system work or would it act all crazy once under power .
Cheers Paul |
Admin (Admin)
Board Administrator
Username: Admin
Post Number: 1188
Registered: 10-2004
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| Posted on Monday, January 18, 2010 - 4:57 pm: |
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Paul,
We do not have any transaxle type arrangements. The driving method you then mention is not uncommon but may give poor results for your application if the front wheels leave the ground. This effect is lessened by you having a long chassis with the wheels close together so may be acceptable compromise. |
