Increase the chain speed/rpm of the tranny which reduces the torque loading, and it will never explode. 
I have almost a thousand miles on my shimano tricycle transmission as jack shaft. THere is no sign of trouble or heat.
I recommend the nexus highly over the SA. I crank out 40mph with the shimano in 3rd gear.
	
		
			
		
		
	
				
			I have almost a thousand miles on my shimano tricycle transmission as jack shaft. THere is no sign of trouble or heat.
I recommend the nexus highly over the SA. I crank out 40mph with the shimano in 3rd gear.
	
	
	
	