When making a trolley, one of the most important things is the castors you choose.
The castors you select will determin the limitations of your trolley. Most trolleys idealy work best with 4 x castor wheels. two Braked swivel castors & two fixed castors. most turning circles can be achieved with 2 swivel castors & more often than not if the swivel casters are also braked, this will be more than anouth to stop your trolley from moving, unless you have a very heavey load & your trolley is situated on a steep incline.
Be sure to check the load ratings on the castors you select & add in a safety factor of the total weight caried by 3 of the castor wheels.
ie,
trolley weight = 50 Kg
Trolley will carry 150 Kg
Total Weight = 200KG
Your trolley is a 4 wheel set up, you may be thinking your trolley has 4 castor wheels with a 50kg limit for each wheel. That would be sufficent Right? Wrong, as the 4 wheels can carry the 200 KG, but what if your trolley is on un even ground where only 3 of your castors are taking the weight, ie 200 kg divided by 3 x 50 kg wheels.
Ok, so 3 wheels rated @ 150 kilos are now taking 200 kilos. Your castors are not going to last to long, also this poses a health & safety issue, as you do not want your castors to collapse & cause damage to the goods being carried, or worst still cause injury to some one.