Custom build of a crankshaft trueing stand

[malmac]

Scrape them to fit. Just like a dovetail on a machine.

Joe

Thank you for your suggestion.
It makes me realise I have two stages in the process.
Firstly to try and make them as near as possible to identical.
Secondly fitting them up so that they actually work.

Your suggestion will certianly come in handy as the second step needs to be sorted.

Mal

 

[malmac]

Or slot them part way in from the ends so you could tap in or thread in small wedges to fine tune the fit?

-frank

Hi Frank.

I have attached a diagram of what I think you are suggesting. Is this what you mean or am I barking up the wrong tree?

Mal

 

[francist]

No not quite but I could also see something like that working. What I was getting at was more like below, a slot through the foot at each end that would allow some sort of wedging action to take place and slightly spread the ends of the foot. A tap-in wedge, or in the case of my scribble here a conical wedge with threads that could be wound in or out depending.

This would not be anywhere near as nice a contact area as something like scraping, but I also wasn’t sure how much movement or sliding would really need to occur once you had a position established. It’s also possible I have completely misinterpreted your graphic of the setup, it would not be the first time!

-frank

 

[extropic]

As I understand it, the function of the dovetail ways is to keep the V-blocks aligned while allowing the distance between V-blocks to be changed.
I'm thinking there is an easier way. Instead of using dovetails, think "box-ways". The bases of the V-blocks could straddle a rectangular base or they could guide in a slot in the base. Either of the box-way options only need one flat vertical plane and one flat horizontal plane (not equally spaced angled planes) on each part. Clamp the linear motion with lock screws behind a gib, bearing opposite the vertical guide plane.

I hope that's clear enough. If it makes no sense, let me know and I can generate a rough sketch.

Depending on the precision you're trying to achieve, I'm hoping you have access to heat treating and surface grinding.

 

[malmac]

No not quite but I could also see something like that working. What I was getting at was more like below, a slot through the foot at each end that would allow some sort of wedging action to take place and slightly spread the ends of the foot. A tap-in wedge, or in the case of my scribble here a conical wedge with threads that could be wound in or out depending.

This would not be anywhere near as nice a contact area as something like scraping, but I also wasn’t sure how much movement or sliding would really need to occur once you had a position established. It’s also possible I have completely misinterpreted your graphic of the setup, it would not be the first time!

-frank

Frank, thank you for the wonderful sketch. It really does work better than 1,000 words.
In my case I dont believe that would work because my blocks are 24mm by 48mm and 124mm long.
However if the slot was set closer to one side then maybe it could be an option.

The thing I like about these deliberations is they really get the grey matter churning along.
Like, how much accuracy do we need.

The parts are not going to be moving rapidly or frequently. So wear and tear is going to be low.
The real issue is here is keeping the two legs in alignment.

Mal

 

[malmac]

As I understand it, the function of the dovetail ways is to keep the V-blocks aligned while allowing the distance between V-blocks to be changed.
I'm thinking there is an easier way. Instead of using dovetails, think "box-ways". The bases of the V-blocks could straddle a rectangular base or they could guide in a slot in the base. Either of the box-way options only need one flat vertical plane and one flat horizontal plane (not equally spaced angled planes) on each part. Clamp the linear motion with lock screws behind a gib, bearing opposite the vertical guide plane.

I hope that's clear enough. If it makes no sense, let me know and I can generate a rough sketch.

Depending on the precision you're trying to achieve, I'm hoping you have access to heat treating and surface grinding.

Your suggestions re the box-way option needs to be considered.
Given the ffet will be moved and then locked down with a bolt, I thought the 60 degree angle with one side guide adjustable, would allow me to fine tune the precision based on the amount of drag I wanted when repositioning the feet.
The main problem being then the machining of the two feet to be as near as possible to being the same dimensions.


Thanks for your suggestion.


Mal

 

[malmac]

Well here is the daily update, as I got a bit done today.

I tack welded the two feet together at a point that will get machined off when the feet get their 60 degree cuts. I then drilled two 4mm holes through from the side that don't get the 60 degree cuts.
Then I tack welded the end of two four mill rods that I used to keep the two feet aligned even when the end tacks get machined off.

I then managed to cut the first dovetail. If you look in the pic you can see the tack weld on the end of one of the 4mm rods.
So far so good.

Mal

 

[malmac]

Well here is an update on progress with the trueing stand.

The legs are not attached at this stage but it is starting to take shape.

Mal

 

[malmac]

I plan to have a handwheel on the right hand side / or maybe the left which will wind the legs together or apart.
Here are the taps I made to cut the brass nuts for inclusion in the feet of the stand.
Next step is to machine up the 12mm trazoidal threaded rod which the nut will engage with.

It is the first time I have used tool steel and attempted the harden and temper process..... well I can say I have a long way to go to get that process to a more controlled level.

Mal

 

[malmac]

accidently p[osted the above comment twice. Couldnt work out how to totally delete the post.