centre bolt on a gso ?

[GrahamL]

has anyone had problems with theres ?..my rockerboxes centre hole seems to of become quite loose/worn around the sleave meaning it tends to grab
and wobble rather than move smoothly .

thanks

[gbeal]

Nope, but on my homebrew (read I built them myself) base(s) I incorporate a metal or plastic bush or sleeve. The action after many rotations can wear the soft wood, and this then allows the base to wobble as you suggest. Get a platic or metal bush made, and fitted. This is more so important if you have encoders as the azimuth one will be subject to errors if the base can move rather than rotate.
Gary

[Tannehill]

I have a 12" GSO and even tho it's quite new, because I have disassembled the unit many times, and knocked it around, I already note the smallest amount of slop in the rocker hole due to the abrasion of hte bolt on this bare particle board.

I was looking for a bushing that would work, but haven't found on yet. Some prospects on the mcmaster carr website. I expect I'll need to drill out the hole to make the bushing fit snug in the hole.

Scott

[Tamtarn]

Hi Scott

We have a 12" GSO purchased from Bintel - Melb and it came standard with a centre metal bush. Have also fitted a nylon washer under the bolt head which also helps.
Could be worth checking with Roger in case he has a spare bush.

David

[erick]

Perhaps a new bolt set?

With Scott's ("tannehill") help, I obtained a new bolt set from:-

http://www.astrosystems.biz/pivot.htm

for my 8" dob. The dob had not had much use, so this new bolt with sleeves, teflon washer etc dropped into place quite snugly. It's been performing well.

Perhaps if the sleeve is developing some space between it and the wood, a layer of "contact" wound around the sleeve might restore the snug fit? But that may wear fairly quickly??

[Sentinel]

I haven't got a commercially made dob, but this fix could be retrofitted to any dob. I inserted an enclosed bearing into my rocker base. No slop or friction issues.

See photo attached. It's pretty boring but shows what I mean.

[GrahamL]

thanks for all the input

yes the slop is in the chipboard and I think it happened last time i took my scope on a longish drive . I know the centre nut was a little loose and bouncing around on an uneven surface (car seat) was probably enough .

that bearing fix looks great paul do you have one in the base as well?

My fathers an engineer so I should be able to do something next week on the way to astrofest ..a large bolt through the chipboard is doing ok for now .Know there built to a price but simple sleaves that are secured
laterally sure wouldn't be a big cost increase .

take care

[gbeal]

Heck Graham, if youhave access to a lathe have Dad spin you a plastic "bush", with the hole in the middle a nice fit for the centre bolt, and the outside a suitable size that you can open the base hole to. Piece of cake.

[Sentinel]

No,

Just in the bottom of the rocker, a welded nut in a plate is on the baseboard, with another nut holding the bolt tight.

Cheers.

[jjjnettie]

My bolt comes loose all the time.
Transport the scope, tighten the bolt, observe with the scope, tighten the bolt.
Look sideways at the bloody thing, tighten the bolt.

[GeoffW1]

Hi JJ,

You could try some Loctite threadlock on it. This is a polymer which cures in the presence of metal and absence of air (in the thread). There are various grades, some permanent, some for occasional disassembly. The 248 grade can be disassembled with hand tools and without having to apply heat.

Cheers

[Sentinel]

I had this problem many years back, the plywood of the rocker bottom slowly loosened the bolt as you moved the scope.

The reason the bolt comes undone will be the friction of the rocker on the bolt , however a nylock nut or a standard nut, will lock the bolt to the ground board. Loctite will work as well.

You need to address the cause, not only fixing the effect.

My Azimuth bolt sits slightly higher than the rocker bottom so that the top of the bolt cannot bind on the top of the sealed bearing.

[jjjnettie]

Thanks for the help.