If it's not really about Fabricating in motorsport. Then it belongs in here.
= Resolved threads
I'd like to make a set of vehicle dollies to move my cars around. However, the cost of new castor wheels doesn't appear to make that a good choice. @nigelpetrie I see you have a solid looking set the S15 is sitting on in the strip down video - https://engineeredtoslide.com/2020/10/s15-project-strip-down/. Are those bought or made? If bought what type and if made do you have plans? Cheers.
Prices for castors do vary a lot, but for this application there are at least five things to consider, which may allow you to make an informed decision.
Load capacity - with the weightof the vehicle, each dolly is going to have to take ~25% of the total. For some extra reserve you can use 50%, and as there are four castors you would in theory allow each to carry 25% of that but, again. allowing for some additional reserve, you may wish to use 30-50%. All this means is that each castor may be rated between 6.25% (pushing it) and 25% (huge reserve strength) of the vehicle's weight - I'd probably be looking at something in the 15-20% range.
The rotating mechanism - as a general rule, the larger the supporting diameter of the thrust ring the better, and the point the castor' wheel contacts the ground should be within that circle - otherwise there will be a bending and tensile load on the axis it's rotating about, which can cause binding.
Material - many castors of the required load capacity may be available as solid in cast iron or plastic, or tyred (with a solid rubber tyre) in plastic or steel. The former will be cheaper but will usually run less smoothly - the plastic may also be more susceptible to damage. The tyres versions will normally run more smoothly and quietly but will be more expensive.
Bearing type - most castors will use wheels with plain bearings, the wheel riding directly on the shaft, this can be perfectly acceptable if correctly lubricated. The rather more expensive wheels will have rolling element bearings, and so be much smoother.
Diameter - smaller wheels take up less room, but run lesss moothly. Larger diameter wheels will run more easily but will need to have a 'drop' centre for the vehicle's tyre for clearance. For a low car, there may even be problems getting it under the vehicle's body/chassis.
While my main philosophy is "build not buy", there are some commercially made products that are actually rather cost effective - especially when you take into account labour and the other incidental expenses of doing it one's self. Just give them a good look-over bearing the above comments in mind.
Thanks Gord. That's very useful 👍
As far as load bearing capacity goes, the presumption that each dolly is taking 25% of the vehicles mass is incorrect (unless your vehicle has a perfect 50/50 balance front to rear, as well as side to side). Some vehicles can have up to 75% of their mass over one axle (FWD cars have a forward weight balance, 911's have a rearward balance). Most of the commercially available "go-jack" style units have a working load capacity of ~700 to 750 kg per dolly. their ultimate capacity would likely to be twice that for safety reasons, the curved metal non adjustable dollies that require the vehicle to be jacked up first and then lowered into the dollies are around the 500Kg mark.
Thanks, Stephen. I have corner weighted my car and was going to use the max weight as my benchmark.
Does anyone have any recommendations for dollies?
I purchased mine from Summit, as you said the price of a good caster wheel was expensive and when your looking at buying 16 of them it becomes easier to buy something.
I've had a set of these for my workshop for around 8 years, never had an issue with them, although kincrome have now gone to a ratcheting style system for the dollies.
Superceded hydraulic vehicle positioning jacks.
New units
You also have to think about how you are going to use these dollies, if you are planning on putting the car on them and leaving it there for a period of time, then the ones that require a separate jack to use are going to be acceptable, but if it is in a workshop environment, or you are going to be using them to shuffle cars around often then the self contained units that jack the car up using the unit are going to be a lot more convenient
Thanks Nigel and Stephen. Those are excellent links. Thank you.