Scratch build electric tethered car racer

[Roog]

Oh wow. That would have been a good idear.

I did this, once, I sawed a small piece off in the chuck of my dad's Unimat 3, (a really well made but tiny little lathe) using a Jr. hacksaw, whilst the chuck was spinning.

As the blade cut through it made a lovely neat notch in the lathe bed, something that I had to look at each time i used his lathe thereafter.

 

[WickedFog]

I did this, once, I sawed a small piece off in the chuck of my dad's Unimat 3, (a really well made but tiny little lathe) using a Jr. hacksaw, whilst the chuck was spinning.

As the blade cut through it made a lovely neat notch in the lathe bed, something that I had to look at each time i used his lathe thereafter.

I have a Unimat that belonged to my dad.

 

[Roog]

I really like the bigger ones, but they sought after and expensive

 

[Roog]

Myford Super 7 lathes are very popular amongst model engineers in the UK, what do people aspire to in the US?

Space is a big issue here so a larger ex-industry machine is not as attractive as it might seem

 

[Roog]

Its been a bit slow of late, I am recovering from a medical procedure which has left me in quite a bit of discomfort and not allowed to do physical work. I've been banned from my shed which seems a bit unfair as I am now back to work, albeit in a sedentary job sitting at my home office (box room) desk.

I wasn't even allowed to unbox my new metal cutting band saw which arrived earlier this week Edit: this has now been done by my missus who wanted to make sure it worked OK too! She even moved it to my shed bench top for me to stop me from doing this. She's a good'un.

I am hoping to sneak out the the shed this weekend to finish the one and a half wheels I have machined so far, mostly counter boring holes and thread tapping, nothing to physical.

I am wondering whether to go for counter sunk or counterbored cap head screws to clamp the wheel halves, countersunk leaves more metal in the wheel hub but is harder to prevent chatter when 'drilling/forming'.
I prefer the engineering look and strength of the cap head screws, but the bore will reduce thickness on some edges. the cap head solution will allow some give for centering the wheel halves on the hub, where as the counter sunk screws will try to pull against each other if there is a tiny error in the countersinking of the six point grid layout of the holes. Centering should be under the control of the reamed bores in the wheel halves and the yet to be machined 'carefully' hubs.

I note from looking back at the original wheel halves that they used cap head screws. I'm leaning this way, despite having just ordered a load of M4 countersink screws!

 

[WickedFog]

Countersunk holes are best done at really low RPM and with a lot of pressure (high feedrate). The type of c-sink tool you are using can affect that as well. Solid carbide is your best bet. I never cared for the HSS ones, but there were a few that I have used that were just special, and cut amazingly well.

If you have pins locating the halves together, and are fairly accurate with your c-sunk hole locations, I think the bolt will give before the pins do. So any slight deviation should be absorbed by the bolts.

 

[ahr43]

Good hearing you're on the road to recovery. Yep, that missus is a keeper. Always good when your mate has your back. Working on the tether car will be good therapy.

To countersunk or counterbore? Similar dilemma for me when building my drag racing chassis back '07-'11. Didn't have the ability to counterbore nor the skill to countersink. Settled for straight drilling the hole. Allowed me the ability to adjust for fit over the countersink. Whatever you decide will work, you'll get 'er right. Cheers. -AC

 

[Doom!]

Going to sound like your missus for a minute, Don't overdo it! but I understand, when you have projects and down time, it drives you crazy not being able to work on them. Of course I'm a big hypocrite and would be doing the same as you.

 

[Roog]

Good hearing you're on the road to recovery. Yep, that missus is a keeper. Always good when your mate has your back. Working on the tether car will be good therapy.

To countersunk or counterbore? Similar dilemma for me when building my drag racing chassis back '07-'11. Didn't have the ability to counterbore nor the skill to countersink. Settled for straight drilling the hole. Allowed me the ability to adjust for fit over the countersink. Whatever you decide will work, you'll get 'er right. Cheers. -AC

The chap who builds wheel driven cars at the track just bolts through, its strong but the sight of cap head bolts sticking out from the wheel feels counter intuitive. Like the 'tyre shredder' on James Bonds DB5! (please note English spelling of tire because its 007)

Countersunk holes are best done at really low RPM and with a lot of pressure (high feedrate). The type of c-sink tool you are using can affect that as well. Solid carbide is your best bet. I never cared for the HSS ones, but there were a few that I have used that were just special, and cut amazingly well.

If you have pins locating the halves together, and are fairly accurate with your c-sunk hole locations, I think the bolt will give before the pins do. So any slight deviation should be absorbed by the bolts.

Just the 6 bolts holding this one together, I'm going to have a good look at this tomorrow and decide, but as ever I appreciate your and everyone's comments, especially about feed rates with counter sinking bits, I naturally take it light and back off when it judders.

Going to sound like your missus for a minute, Don't overdo it! but I understand, when you have projects and down time, it drives you crazy not being able to work on them. Of course I'm a big hypocrite and would be doing the same as you.

I know she's right, I had to tell my works that, "no I wasn't going to traipse about a multistorey building with no lifts next week!" (I had to hold my missus back from ringing my office to give them a piece of her mind!)

A short walk to my shed to drill some holes might be OK though.

 

[WickedFog]

I naturally take it light and back off when it judders.

That's the exact opposite of what you should do in most instances. Lower the RPM and drive it home. Do some test holes in a piece of scrap. Make sure you are choked up as far as you can on the bit too. Snug your quill clamp down a bit so it takes up some of the play in your quill. Make sure your table is locked down tight too.

 

[Roog]

That's the exact opposite of what you should do in most instances. Lower the RPM and drive it home. Do some test holes in a piece of scrap. Make sure you are choked up as far as you can on the bit too. Snug your quill clamp down a bit so it takes up some of the play in your quill. Make sure your table is locked down tight too.

Thanks I’ll give this a go

 

[Roog]

Both new wheel halves nearly complete

I think I’ll go with counter sink screws for the six clamping screws, so I’ll wait until my order of screws arrives before carrying out the counter- sinking.

Next on the list to build, “the hubs” my previous wheels have avoided separate hubs because it introduces more parts and fixings, but I can see the advantage that the hub can be made from steel.

Looking at the thin tires I am beginning to get concerned at the cost of running these as i can't see them lasting long. Mind you barely a track visit goes by with out me making a new set of wheels!

 

[Roog]

Now we have hubs, I’ve been machining so much aluminium of late that I’d forgotten that tools wear!

I still need to mill the drive engagement slots in the back of the hubs and lots of M4 holes to tap, needs a clear head to do this delicate work, so I'll leave that for another day.

 

[Roog]

Here they are, 'new wheels'! So help me.

My wheel designs are defiantly getting fancier. Not quite as thin as the one I had as a pattern, but I always add a bit for safety, I'd never make a good aircraft designer and I don't understand how they have got so scratched up already.

And 'dry assembled' on car, the larger diameter brings it quite close to the motor and puts the car on a jaunty 'nose down' pitch, all by design of course.

Waiting on a new drive belt due to my change to a larger diameter drive pully.

Also up rated the front suspension spring which looks surprisingly knackered given that it has only seem a handful of minutes run time.


Sadly I have just missed the track day this month, I might ask if I can make use of it in a private session.

 

[WickedFog]

Awesome man. Can't wait to hear how it goes!

 

[Doom!]

If they perform as good as they look, you are i for a real treat. I can't wait to hear how they do.

 

[Roog]

Awesome man. Can't wait to hear how it goes!

In theory these tires should hold up, (LOL) it would be nice to get a few laps in with out seeing bits of rubber flying off.

Fingers crossed.

 

[WickedFog]

In theory these tires should hold up, (LOL) it would be nice to get a few laps in with out seeing bits of rubber flying off.

Fingers crossed.

I think the design you have now is way better than what you had before. Those ridges inside will keep that centrifugal force from being able to expell a tire much better than before.

 

[Roog]

I think the design you have now is way better than what you had before. Those rodges inside will keep that centrifugal force from being able to expell a tire much better than before.

I am reasonably confident this time