24 Volt Motor Control w/ 12 Volt Timer

I am new to this forum but it looks like the place to go for advice so here we go. I am building an automatic feeder that requires the use of a powerful motor so I bought a 24 volt wheelchair motor off ebay. I am using the 12 volt timer to actuate a relay which starts the motor. My first attempt worked a couple of times and then ruined the timer. I am guessing the problem might have been because I did not use a relay with diode protection. I have a crude schematic of how I am planning on wiring my next attempt but I would appreciate any comments so maybe I wouldn't burn up another $60 timer. Thank you in advance

 

Alec_t, thank you very much for the reply. Getting a larger relay is no problem but the MOFSET is out of my league. I have been reading on them but its not soaking in. Would I need an n or p channel, depletion type or enhancement. Ill keep reading

 

Thank you both for replying. I can find no data for the timer other than it operates on 6/12 volts and is fuse protected with a 15 amp fuse. One other issue I noticed was that the relay was not staying latched in and it was clicking rapidly. A check with the voltmeter confirmed it was opening and closing rapidly. This was with the original timer that quit working so maybe that was causing this. I attached a photo of the relay as well

 

Thanks Bluejets, The timers come with 4 wires. 2 for power and 2 for motor. I have nothing else connected except the relay in place of the motor. As soon as I get my parts I am going to give this another try. If you guys don't see anything terrible wrong with this circuit I'm going to blame the old timer as the problem. Thanks for the help