Any IRTE Experts ?

[moonbase]

Hi,

I have a problem with an IRTE polar mount in that it seems very stiff to hand swivel it East/West.

If I remove the declination plate, the top and bottom bearings rotate freely in their housings. However, once I put the declination plate back on the polar mount and tighten up the fixings the bearings do not rotate at all in their housings, the only rotation is that of the bolts passing through the bearings. My understanding is that the bearings should rotate in their housings and not the bolts passing through the bearings?

I am reasonably sure that I have put the polar mount correctly assemble but am not 100% confident on that point. I am puzzled why the bearings are not rotating in their housings when the nuts/bolts are tightened up? The bearing type looks to be a single ball in a housing socket rather than a circular array of small ball bearings enclosed in a round casing.

The bearing housings are square, surface mounted and riveted to the frame. I suppose I could remove the rivets and replace the bearings but if there is a simpler solution it would be preferred. Any advice to resolve the issue will be most welcome.

I have attached a few pics of the bearings.

 

[jeallen01]

No way am I an IRTE "expert", but I would suspect that the holes in the bracket for the bolts are not exactly aligned and so the centres of the holes are not exactly the same distance from the long face of the bracket of which they form part,or else one or other end of the bracket is not at exactly 90 deg to the long face. Thus, when the bolts are tightened, one or other of the bearings is pulled slightly out of line with the other -> the bearings then don't have a common axis and they then temporarily "seize" up (or something like that).
PS: could also be wear in the bearings (?)

 

[Channel Hopper]

You broke it.
Ill have some time to take a better look tomorrow afternoon at the two here. it's a bit dark outside.

 

[moonbase]

.... Thus, when the bolts are tightened, one or other of the bearings is pulled slightly out of line with the other -> the bearings then don't have a common axis and they then temporarily "seize" up (or something like that).
PS: could also be wear in the bearings (?)

The bottom bearing has sideways movement as well as rotation about its central axis. It has to have sideways movement to be able to adjust the declination offset angle on the top part of the mount. The sideways movement allows the top and bottom bolts to be in line, or rather it should allow them to be inline.

The top part of the bracket does not have a circular hole for the bolt, it has a channel that allows the top part to have backwards and forwards movement to set the declination offset angle for geographic location. I have attached a picture below that shows the channel on the top part of the bracket.

 

[jeallen01]

FWIW, sounds like a "cr*p" design in the 1st place, &/or you need more practice at making those minute adjustments to get it right!

Definitely "not going there" with an IRTE mount!

 

[moonbase]

FWIW, sounds like a "cr*p" design in the 1st place, &/or you need more practice at making those minute adjustments to get it right!...

The design is similar in principle to that used by Precision Antennas when they were manufacturing satellite equipment.

Both the Precision Antennas and IRTE design consists of an inner frame and and outer frame with the inner frame having surface mounted bearings. The outer frame is the part that pivots East/West and has the declination offset angle scale at the top. The inner and outer frames are connected via bolts that pass through the bearings on the inner frame.

 

[Channel Hopper]

FWIW, sounds like a "cr*p" design in the 1st place, &/or you need more practice at making those minute adjustments to get it right!

Definitely "not going there" with an IRTE mount!

Like cockroaches and VW Beetles, the IRTE polarmount will be one of the few things remaining in a nuclear wasteland.

 

[moonbase]

Some progress, not a solution but possibly an identification of the problem?

I removed the declination plate to expose the top and bottom bearings then tested them for rotation. Without any fittings both bearings rotate freely. If the bottom bearing is fitted a bolt/washer/nut and tightened with spanners it still rotates freely on its axis and has its intended sideways movement. However, the same fitting of bolt/washer/nut to the top bearing with finger tightening starts to impact the rotation of the bearing on its axis. If it is tightened with spanners the rotation is very stiff.

It looks like the top bearing is being compressed in the housing with a resultant loss of rotation? As I am not familiar with the IRTE polar mounts I am not sure if this is normal or if I have a fault with the top bearing.

The bore for both top and bottom bearings seems to be an odd size as they measure 12.45mm with a vernier caliper. However, I suppose I could replace the top one with a 12mm bore bearing or a 1/2" bore bearing subject to availability. Due to my lack of knowledge on bearings I dont know what the correct type is to to look for. At a guess it is some type of 4 bolt flange bearing? The top bearing does not have the sideways movement that the bottom one has, it only has rotation on its bore axis. Although the top and bottom bearings look similar they are in fact different.

I have attached a few pictures below. Any help in identifying the top and bottom bearing types would be gratefully received.

 

[Channel Hopper]

I believe you might have missed out a spacer, or possibly inserted a washer in the wrong place.
Give me an hour to take some images of the spare.

 

[Channel Hopper]

Hopefully from these you can work out if you have the spacing wrong (possibly upside down ?)

Both top and bottom have a gap of exactly 2mm.

 

[Channel Hopper]

It looks like you are missing the spring washer on the bottom bearing

 

[moonbase]

CH,

Many thanks for the pictures. Is there any chance you could take a less close up picture so that I can see the full configuration of the dish/declination plate with respect to the pole cap frame it bolts to.?

I found the spring washer, it dropped of when I was assembling the mount and rolled yards away, they are never close to where they fall.

 

[Channel Hopper]

I'm on the roof in an hour so will take pictures of the existing mount that has been in operation since 1993.

 

[Channel Hopper]

The mount on the roof appears to have two additional spacers on the lower bearing bolt.

 

[moonbase]

The mount on the roof appears to have two additional spacers on the lower bearing bolt.

CH,

Many thanks for your kind input, that picture of the two additional spacers on the bottom bearing could be where I am going wrong. I will try it with some more spacers to see if it resolves the issue.

 

[moonbase]

...&/or you need more practice at making those minute adjustments to get it right!...

You are possibly right that I need more practice to assemble the IRTE polar mount correctly. I openly admit in my "install" topics that I am a bodger at jobs relating to hobbyist satellite equipment. However, from advice kindly given on this forum over the years I have got to the stage where I can setup a Jaeger 1224 H-H motor and a Precision Antennas polar mount to accurately track a satellite arc with dishes ranging in size from 1.2m to 2.2m.

I would have given your above comment more credence had it come from someone who was capable themselves at accurately installing a motorised dish. However, are you not the person who could not accurately install a TD110 dish dish on a DiSEqC motor and had to get someone round to sort it out for you?

Advice Needed - DiSEqC motors - Just how much longitudinal angular position accuracy can you reasonably expect?

I notice that your original signature was updated after you had someone round to install the TD110 correctly for you

Several receivers and a few dishes - the steerable Triax TD88 got about 53E to 31.5W, but the "new" TD110 seems to be having problems at the extreme ends of the same arc, even though it seems to be tracking pretty well inside that arc???

Several receivers and a few dishes - the steerable Triax TD110 now definitely gets 53E to 45W! (especially after CH's expert readjustment of the dish & mount...

You are welcome to come back with your contribution after you have successfully setup a polar mount to accurately track an arc on your own. However, until then in my personal opinion you are out of your depth on this subject.

 

[Lazarus]

Mod. Note

We will take a dim view if this Topic takes a tit-for-tat course.

Keep it civil please, chaps.

 

[moonbase]

Udpate:

I tried the additional two spacers that were present in the photo kindly uploaded by "CH", unfortunately I still have the same issue with the top bearing. As soon as there is any tightening up of the dish/declination plate the top bearing gets harder to turn. There is no such issue with the bottom bearing.

As the top part of the dish/declination plate needs to be clamped in place to keep the declination angle locked I tried a bodge job to keep it locked but still have the dish/declination plate easily movable East/West. The bodge job involved hybridising the top plate of the IRTE mount into a garish version of the top plate of a Jaeger 1224.

The Jaeger 1224 uses an M10 eye bolt to set the declination angle, my garish bodge job attempts to use the same logic. A picture of the garish bodge job, now known as the "IRTE-1224 Hybridisation" is attached below. It seems to lock the declination angle and allow easy East/West movement. I need to tidy it up and cut the bolts to correct length.