Gina's Observatory Build - Abbreviated - Finishing Touches and Improvements

[Gina]

The problem with studding is that it won't fit snugly in the centre hole in the workpiece.  A problem I've been having with the loose fit from making oversize holes in the stock is that the insides and outsides are not concentric.  The mandrel really needs to be a close fit in the hole in the workpiece.

Actually I've had another idea - cut the head off a part threaded bolt, put it in the chuck and tighten the workpiece up against the chuck jaws with nut and washer on the RH end.

[Gina]

[Tinker1947]

How about thread the hole in the centre and screw the studding through then a lock nut either side, when the work is finished bore out the centre hole to the correct size....

[Gina]

How about thread the hole in the centre and screw the studding through then a lock nut either side, when the work is finished bore out the centre hole to the correct size....

Believe it or not, I thought of that

[Lonestar70]

Hi Gina,

Happy New Year.

I'm thinking of turning a special mandrel to hold in the chuck, like this :-

Maybe aluminium for easy turning or perhaps mild steel might be better.  Is there anything wrong with using aluminium?

It is unfortunate that you have found out the hard way that concentricity is a very important thing to consider when turning this sort of job.

Using any sort of bolt/studding as a mandrel will rarely work very well for 2 reasons.

1. the bolt/studding will not be a close fit in the bore.

2. a 3 jaw chuck has a natural built in eccentricity (runout), usually only a thou or two

but never the less it will always be there.

The only way to get everything absolutely true is either to use a collet chuck (which you dont have) or to turn a mandrel to suit the job dimensions and LEAVE IT IN THE CHUCK until all operations are finished.

You are on the right track with the mandrel shown in your sketch (above), however, it is not really necessary to turn the chuck side down so far... just take a light skim to true the material to round and reverse it in the chuck for the reduced end.

If I were doing this I would make the mandrel long enough for a single wheel for reasons I will expand on later.

Turn the end down tyo a very close fit in your wheel bores (I am assuming they are all exactly the same size), but make the stub a little shorter than the width of the wheel (say 1/32" or 1mm)... square up the shoulder once you have achieved the correct dia.

Drill and tap the end of the stub say 6mm or 8mm for a depth of about 1" (25mm).

Now, using a centre punch... put a mark on the material in the chuck right on front of the NUMBER 1 JAW... this can be used as a reference in replacing the mandrel in the chuck at a later date... for now, just leave the mandrel in the chuck.

ALI, or Brass will be perfectly OK for a mandrel... no need for steel.

Put a wheel onto the mandrel and lock it using a suitable 6mm or 8mm bolt and a large washer.

Take a light skim over the OD to true it with the bore... take note of the crosslide dial setting for the final OD... repeat this for all  the wheels... taking each one to the same crosslide reading

Do the rough shaping of the vee on ALL the wheels using your current method... leaving the last one on the mandrel.

Set up the topslide angle and align the tool ready for the start of the final Vee cleanup.

LOCK the CARRIAGE and leave it locked until all finished.

Clean up the first vee face to finished dimension putting feed depth on with the crosslide handwheel... cut/turn with the compound.

when you get to the finished dimension take carefull note of the crosslide dial number (write it down)

withdraw the crosslide and unbolt the workpiece... flip it round 180deg and put back onto the mandrel and tighten up.

Face up the remaining Vee side as before and take it down to the same crosslide setting... thus both sides of the vee will be identical.

The advantage of this method is... you only need to set the angle once and only in one direction.

Repeat for the remaining wheels without unlocking the carriage.

All wheels should now be exactly the same OD and the Vee grooves will be of identical depth and width and all will be concentric.

Doing them this way allows you to lock the carriage and make full use of the handwheel dials... which would be almost impossible if you were using 2 wheels on the mandrel... especially with an angled cut.

Hope this helps.

Best regards.

Sandy.

[Gina]

Thank you Sandy - that's very useful

[Gina]

I tried out one of the new wheels with the offcut of aluminium angle and it seemed to work fine   Of course, I won't know if the ROR will move more easily with the new wheels until I have all four in place

[Gina]

I think I shall have to invest in an electric bilge pump for the foundations of my obsy, then in the spring or summer arrange better drainage   The big beams supporting the joists of the floor and sitting in water

This automatic bilge pump looks alright - I could connect it to the 12v car battery I use for the winch.  Flood water removal even with a power cut   Yes I AM serious about this - I need to do something.  Lowering the bank behind the obsy is not very practical due to the weather itself.  Anyway, it would need a lot of digging.  I think if I placed the pump just below the beams it should remove the troublesome water while letting any mud sink to the bottom.

[Gina]

I think this bilge pump at just £3 more would be better as it mentions a filter.  There is no mention of a filter on the cheaper model so I must presume it doesn't have one.

[Tinker1947]

Place the pump in a hollow so its the lowest point it should then keep all water down the its float switch level...

[Gina]

Place the pump in a hollow so its the lowest point it should then keep all water down the its float switch level...

Yes indeed   It's ordered and due to arrive Thursday.

[Gina]

The bilge pump arrived today as expected   Looks fine.  I've looked at the obsy ground plan and the lowest point is just in front of the pier base.  I'm looking into this further but ATM it looks like the best way to get the pump in position would be to make a hatch in the scope room floor for access.  I'll post pics tomorrow.

[Tinker1947]

Can the pump not got outside at the lowest point, in a small pit so all water from under the Obyy will run out there..

[Gina]

Can the pump not got outside at the lowest point, in a small pit so all water from under the Obyy will run out there..

Not without a lot of digging

I made a serious mistake on the foundations   Very serious!  I guess I was too keen to get to the building stage and didn't plan for continuous deluges of rain - I should have built the whole thing higher up.  But I wanted to keep the shed's profile as low as possible - appearance was paramount.  In fact during the build I found I had to change the floor support arrangements.  That was after I'd built the pier and then with the floor being higher, the pier wasn't as high as I had intended   If I were building it again there are several things I would have done differently but I guess that's not unusual.

I'm not sure now if draining the lowest point would reduce the water level all over to below the bottom of the beams but it might.  Time will tell.

[Gina]

Here are some pics that show the foundations.  The last one shows a possible access point.

Just taken some photos by putting my camera under the floor using the gap shown above.  This is the best one.

I'm going to try to get the pump in through here to the lowest place just in front of the pier and run the outlet out the other side and up over the bank and into the field.

As can be seen water does drain away and most of the time there is no problem - normal rain water just drains away through the ground.  It's when we have torrential downpours that the foundations flood and we seem to be getting more and more of these.

[StevieDvd]

Turn a negative into a positive, make it into a moat and you've got added security

[Tinker1947]

yep, a moat with some crocodiles that's the way to go......

[Gina]

It becomes a moat at times - I even have a drawbridge    Actually, the whole area is turning into a swamp - we have water plants growing round the obsy and along our southern (down hill) boundary!!!   And it's started raining again

[StevieDvd]

It becomes a moat at times - I even have a drawbridge    Actually, the whole area is turning into a swamp - we have water plants growing round the obsy and along our southern (down hill) boundary!!!   And it's started raining again

Next project a boat then. The new must have for UK astronomers

[Gina]

Next project a boat then. The new must have for UK astronomers

If I did, it wouldn't be the first boat I've built   In my very much younger days I used to be into dinghy sailing and racing.  My first boat was a 9ft dinghy I built in the dining room   Living in Portsmouth I was able to make use of driftwood to help with the cost   It was an all wooden boat - none of you more modern GRP

[Gina]

If I was into boatbuilding I would have a ready market a few miles down the road in Somerset where boats are greatly needed   Very bad floods still

[Gina]

If I hadn't had to go out yesterday afternoon I think I would have got the bilge pump imstalled and this afternoon looks like I would have had a chance to test it for real   I'm not going out in the rain, crawling about on the ground to get the thing installed - so there!

[Tinker1947]

Move to Norfolk, my ground is silty, water soaks away faster than it can fall, rain today dry tomorrow, nice and sunny atm white fluffy clouds not sure if i should go in the workshop and do a couple of hours or have a afternoon nap....decisions all the time...

[Gina]

The lathe is back together after replacing the gears and bearings in the headstock and a full strip down and readjust/clean/lubricate.  I have started making a mandrel for turning the obsy ROR wheels yet to be done.

[Gina]

I have sawn a hole in the floor with a large hole saw and can now see what's what   Not a perfect position as a joist is in the way - so much for measuring up from the plans - but I can cut another hole to make enough room to get the bilge pump through.  It is not practical to put the pump in place from outside the obsy as the "lawn" is a large mud wallow   I don't want to disturb the mud too much or it will end up under the obsy!