Pulsar Dome assembly

[Paddy Herbert]

I acquired a second hand Pulsar dome recently and am stuck on the correct assembly of the roller wheels. is it "A" or "B" in my sketch. Also the abutment flanges to the quadrants seem very close to the wheels. Every thing is not tightened up yet, so this might improve.

Thanks in advance, looking forward to future exchanges.

[upahill]

 

This is how mine was assembled, and how I put it back. Seems the same as your left design.

I cant see the part that your drawing is indicating its rubbing on.

Also, im sure its just the drawing, but would opt for the dome head on the bolts to be out the exterior of the dome for asthetics.

Edited July 23, 2019 by upahill

[Paddy Herbert]

Thanks for the swift reply, thats one mystery dealt with. The rubbing problem occurs where the wheel coincides with the dome quadrant junction flanges are bolted together (top of my sketch showing first bolt position in background elevation)

If you could photgraph that location in your dome that would be great.

thanks again

[upahill]

Ah, my dome is a slightly earlier one I think, all in one piece. I wish it unbolted but its solid.

If you have no adjustment in the bolts, and its only the flanges that are rubbing I would say a few minutes with a file would probably be all it takes. A few mm off the edge shouldnt affect anything and will stop the rubbing.

Im actually looking for replacement rollers for mine, if you ever do the same and find they have worn you may need to create additional clearance anyway.

 

The plate that is attached to the dome itself I never removed, nor did I remove the top wheels at all - so im unsure if they are chemically attached, but if not its possible perhaps that there is some play available to adjust - do all wheels foul on the flange? Could it be alignment of the dome pieces setting one edge ever so slightly lower than the other?

Ill try doing a pic to illustrate what I mean.

[upahill]

[upahill]

Actually that makes no sense, forget what I said. I cant work out where the flanges are unless you have a wheel directly in line with one I cant see how they are rubbing on anything. My pic above if looked at upside down could still be relevant.

[JeremyS]

7 minutes ago, upahill said:

Im actually looking for replacement rollers for mine, if you ever do the same and find they have worn you may need to create additional clearance anyway.

I'm also looking for replacement rollers for my 7ft Pulsar dome (also a single piece dome - not the newer bolted together dome). I asked Pulsar, but they haven't been able to suggest replacements yet as the newer models use different rollers it seems.

Do let me know if you find a source, @upahill 

[upahill]

2 minutes ago, JeremyS said:

I'm also looking for replacement rollers for my 7ft Pulsar dome (also a single piece dome - not the newer bolted together dome). I asked Pulsar, but they haven't been able to suggest replacements yet as the newer models use different rollers it seems.

Do let me know if you find a source, @upahill 

Will do, I suspect the bearings are standard and cheap, may even find a suitable material for the roller and try cutting it on the CNC

[JeremyS]

1 minute ago, upahill said:

Will do, I suspect the bearings are standard and cheap, may even find a suitable material for the roller and try cutting it on the CNC

Great  - many thanks! One of my rollers has de-laminated. I.e. the plastic roller "tyre" has cracked and come off the central part where the axle goes. Fortunately it has no effect on the rotation of the dome, but I fear others will undergo the same before too long.......

[pmlogg]

How about these as replacements?

https://www.castors-online.co.uk/acatalog/80mm-Blue-Elastic-Rubber-Wheel-Only-with-12mm---Roller-Bearing---Bore-PL50WVGRBJM6.html?gclid=EAIaIQobChMI35XfqbXL4wIVTbTtCh0WKwYKEAQYASABEgKef_D_BwE

 

[Paddy Herbert]

9 minutes ago, upahill said:

Actually that makes no sense, forget what I said. I cant work out where the flanges are unless you have a wheel directly in line with one I cant see how they are rubbing on anything. My pic above if looked at upside down could still be relevant.

No you are correct, the wheel bracket also bolts the quadrants together. see photo.  I will just pare back as necessary to free the wheels

[upahill]

2 minutes ago, pmlogg said:

How about these as replacements?

https://www.castors-online.co.uk/acatalog/80mm-Blue-Elastic-Rubber-Wheel-Only-with-12mm---Roller-Bearing---Bore-PL50WVGRBJM6.html?gclid=EAIaIQobChMI35XfqbXL4wIVTbTtCh0WKwYKEAQYASABEgKef_D_BwE

 

They look right, will need to take some measurements. Would want the same size so I dont have to redrill all the mounts.

[upahill]

@Paddy Herbert ah that makes sense then. Yeah file it is Although you may have that extra half mm in the bolt holes themselves - I know I did, and if you can loosen them, whilst simultaneously lifting the dome, pulling the bracket and re-tightening it might do it.

[JeremyS]

4 minutes ago, pmlogg said:

How about these as replacements?

https://www.castors-online.co.uk/acatalog/80mm-Blue-Elastic-Rubber-Wheel-Only-with-12mm---Roller-Bearing---Bore-PL50WVGRBJM6.html?gclid=EAIaIQobChMI35XfqbXL4wIVTbTtCh0WKwYKEAQYASABEgKef_D_BwE

 

Many tks for the suggestion. As @upahill says, they look right. I measured mine to be 50 mm in diameter.

[pmlogg]

The Pulsar/Rigel rotation drive on my dome has a guide wheel which look pretty much the same as yours and it is 50mm diameter - but not sure about the bore; most of the Pulsar bolts, e.g. for the rollers on mine (quite different from those in the image)  are 8mm and Paddy's photos look like they are probably 8mm.

[upahill]

No calipers handy but just slid a 13mm spanner over the nut on the wheel, that would indicate an M8 bolt I believe.

The only option I have found so far outside of china are these - https://www.bilcastors.co.uk/product/bzl50wvgrbjm828/

50mm OD / 8mm Bore / Ball Bearing.

Of course, im assuming these have ball bearings but they could be plain bores under the plate which would make life simpler.

 

[JeremyS]

On 23/07/2019 at 21:42, upahill said:

They look right, will need to take some measurements. Would want the same size so I dont have to redrill all the mounts.

Did you get anywhere with the replacement rollers for the dome @upahill?

It's on my to-do list this Spring to replace the rollers on my Pulsar dome. 

Not looking forward to undoing the corroded nuts & bolts that hold them on!

[Peter Drew]

Spray some "Plusgas" on them now and they will be ready for Easter.     🙂

[sloz1664]

On 02/03/2020 at 16:01, Peter Drew said:

Spray some "Plusgas" on them now and they will be ready for Easter.     🙂

Plusgas, nothing bears it. I first came across it 28 years ago and was used to unseize bolts in a harsh foundry environment.

Steve

[JeremyS]

On 23/07/2019 at 17:09, pmlogg said:

How about these as replacements?

https://www.castors-online.co.uk/acatalog/80mm-Blue-Elastic-Rubber-Wheel-Only-with-12mm---Roller-Bearing---Bore-PL50WVGRBJM6.html?gclid=EAIaIQobChMI35XfqbXL4wIVTbTtCh0WKwYKEAQYASABEgKef_D_BwE

 

I ordered these over the week-end, but the company phoned today to say they are out of stock. The manufacturer is in Italy so they've no idea when they will be shipped.

Teaches me for not having ordered them last summer!

[JeremyS]

So the wheels arrived today 🙂

They are a bit narrower tread than the existing ones, although the diameter is correct. I think they will ok.

So the first job was to remove the bolts holder on the existing wheels. I had already primed with Plus Gas and added some more for good measure. Some of the bolts are corroded, so I started with a non-corroded one. Using a spanner, I released the nut and got it moving. But then it stopped. The problem is that the whole bolt rotates freely. Ideally I would have liked to use a screwdriver in the bolt head to stop this rotation while working the nut with the spanner. But the bolts have a smooth domed head - no slot!!!

I could try and grip the bolt with pliers, but what would likely damage the bolt thread and I'd never get the nut off.

Any suggestions?

[Physopto]

Better use a grinder to cut through the nut and bolt whilst it is re-tightened  to stop it rotating. This will protect the fibreglass dome from being damaged.

OR, you could try to cut the domed head off very carefully so as not to damage the dome finish.

Next  idea is to re-tighten the bolt and cut through only the bolt protruding past the nut. Then soak in WD40 for a while to allow proper penetration. BUT there is still the  possibility to do some damage to the dome.

There is one last possibility and that is to slip a metal shim behind the domed bolt head then use Mole grips to hold the domed bolt head very tightly. With a liberal coating of WD40 and cutting off the unused bolt it may be possible to undo the nut a bit re-tighten and keep doing that until the nut comes off.

I am ruling out any form of heating as the damage to the dome can be catastrophic.

There is one last possible method and that is to centre punch the domed head in the middle. Followed by drilling a small pilot hole in about 1/4" deep. Then use a drill the same out side diameter as the bolt and drill through the dome. The bolt should just fall off the head.

 

Best of luck.

Derek

[Swoop1]

Use mole grips to clamp the last centimeter of the bolt. Lube the thread grip side of the nut. Undo the nut as far as you can, lube the thread you have just exposed and retightn lightly. Repeat until you can get sufficient progress up the bolt to reach the grips reasonably easily. Cut of the thread mangled by the grips and then undo the nut, using grips on the bolt head if you need to.

[markse68]

On 09/05/2020 at 17:31, Physopto said:

There is one last possible method and that is to centre punch the domed head in the middle. Followed by drilling a small pilot hole in about 1/4" deep. Then use a drill the same out side diameter as the bolt and drill through the dome. The bolt should just fall off the head.

That's what I'd do- least effort and risk of damage to other bits. Buy A4 SS replacements and nuts so you don't have the same problem next time. Guessing they are coach bolts with square shanks- well the one that spun no longer has a square hole to fit into so best get slotted or allen socket heads

[tooth_dr]

Hi Jeremy

If this mine I’d cut a slot in the round head with a Dremel and use a large flathead screw driver and a spanner. Stick a bit of masking tape on the dome around the round head in case the screw driver slips off when loosening. 

Edited May 10, 2020 by tooth_dr