Woodsmith· Admin: 'one of many'
Discussion Starter · #41 ·
It's a senior HRH too so I am quite nervous in case my stuff isn't up to scratch on the day or security have an issue somewhere.Woody,
Great news about HRH. Post a picture on this site if you can.
I can use a bigger drive pulley to get almost any speed but I was working on 4:1 or 3:1 reduction as a starting point. Also I am not sure what rpm the motor will pull yet.Sound like you have the motor set up well in hand. what you describe for drive shafting should do the job. Think about an overdrive jackshaft set up to maybe try to get the top speed up around 5mph. Over all it would be more usable. Belt drive should be fine.
Couple of questions about the Tractor Thingy (called TT in the future).
Does the TT
- Have a real differential? Yes.
- Have any kind of brakes? No, But I was thinking of a transmission brake on the drive pulley or use the plug braking of the controller.
- Have a reverse? No, but I can reverse the motor as the brushes are neutral set for its design voltage.
- What size will the OD of the final rear wheels and tires be? I am thinking of starting off with a set of old 205 55 16" tyres off my car on steel rims giving a 23" diameter but it will depend on getting suitable rims cheap, otherwise whatever else I find.
- What will the center to center width of the final rear tires be? Not sure yet, will see what the wheels are like and then I will make spacers, figuring on about 24" centres to a maximum width of, say, 30".
- What diameter front wheels? I have a pair of 8" diameter trolley wheels or I can use the 15" diameter wheels that came with this axle.
- What is the planned width (center to center of the tires)? As above.
They are just the budget ride on mower type where an 'L' shaped rod doubles as king pin and axle threaded through folded tin work. The steering is another 'L' shaped rod that gives 2/3 turns lock to lock.Suggestions:
See if the lawn tractor yard might not have a couple of usable spindles or even a completefront axle with wheel and tires. The spindles alone will save you half of the figuring and work because the ackerman steering offset and KPI is already built into the units.
Thank you, that would be wonderful. I am sure we can blag customs into letting though a late Christmas present.If you are going totally from scratch a good general spec. for the ackerman steering offset is 15 degrees per side and a good general KPI is also 15 degreese. For the standard garden tractor front wheel that will put the SAI contact close to the center of the tire with a 2 degree +- camber.
From there, once you know front and rear tire diameters it is easy to set up caster, trail, camber and SAI.
I know you might be saying, is this needed on something only going am couple of miles an hour? But I bet that in the end it will go faster, plus it will be heavy with the batteries so you might as well make steering as acurate and easy as possible.
Check on what if any costs if any are involved import wise if I were to send you a pair of spindles as a gift. They would probably be classed as used auto parts or some such. I have three or four pair sitting around that I will never use. I don't think the shipping would be too bad. I'll weigh them and see.
I can appreciate the preference for good steering due to the weight and future fun factor so good spindles would be a great starting point.
I will look forward to it.As far as the Big 13, I guess I better start a build thread. I'll take my camera over with me next week and snap a few of the motor worl we are doing at the shop.