EQ6 belt drive modification

[ncjunk]

Its more the position of the pully on the motor shaft causing the belt to rub on either the upper or lower face of the slot the belt runs through.

I haven't checked where it is rubbing but i think moving the pully down the shaft will fix it, it is a slight swishing noise it is not a major rubbing or grinding noise.

The belt and two pullys are actually working perfectly together...so a very small adjustment will fix it.

[malc-c]

Its up to you - you can either stick with the same ratio (if you can source the 47 toothed gear) or you can go for a 5:1 ratio

For a 5:1 ratio on an HEQ5 you would need to set EQMOD up with the following parameters:

Total Steps = 8640000

Worm Steps = 64000

Tracking offset = -28

For a 4:1 ratio on an HEQ5 you would need to set EQMOD up with:

Total Steps = 6912000

Worm Steps = 51200

Tracking offset = -211

However with the 4:1 ratio you would be operating a long way away from the original values the mount is designed around and you may find that the max slews at a much faster top rate (this isn't controlled by EQMOD - the mount makes its own mind up how fast to go when slewing to a target and of course it doens't know you've changed the gearing!)

[Edit] Just for completeness I'll give the HEQ5 6:1 values

Total Steps = 10368000

Worm Steps = 76800

Tracking offset = 80

Chris.

Chris,

One thing I'm having difficulty in is getting the smaller pulley (12t) bored out to 5mm without run through or off centering. What impact would dropping down to a 4:1 ration have on the HEQ5 mount ? I'm thinking of using a 15t motor pulley with a 60t axis pulley

[chrisshillito]

Malcolm,

Unfortunately no one has ever tried this so to be honest I can't say for certain what will happen. Certainly by using a lower ratio the ranges of all the "numbers" used will be lower than those that apply when using the standard ratio so there shouldn't be any problem with the mount controller rejecting "out of range" data. If the mount controller firmware behaves as I expect it to then using a 4:1 ratio will give you a lower pointing resolution (0.1875 arcsecs compared with 0.15 arcsec with a 5:1 ratio) and a faster slew during gotos or parks.

The faster slew (I think it would be at around 4.4 deg/sec compared to 3.3 deg/sec for the standard gearing) means the mount will inevitably gain greater momentum and I suppose this could affect the motor controllers ability to brake as it will be applying a stopping distance designed for a 5.2 ratio. I guess that so long as you're not at the top end of the mounts load capacity this won't be a problem (and even then there's probably some contingency built in). If the slew speed does cause a problem you could always use EQMOD's slew limit feature to set the maxium slew and park speeds (although this isn't recommended for unattended use).

You may loose some accuracy on the some of the manually selectable slew rates - so x32 may not be exactly x32 but so long as sidereal rate is accurate this really shouldn't be a problem.

Chris.

[malc-c]

Chris, thanks once again for the reply. If I follow your comments correctly, the higher the ratio the better the accuracy / pointing resolution, with a trade off against slewing speed.

Part of me wants to run out and buy a mini-lathe so I can make these myself and see how each combination works in reality, but trying to justify spending close on £600 which we can't really afford (especially with Christmas around the corner) to the other half is proving difficult.... It would also mean that I would need to make up a lot of "kits" to recover the investment, and I don't think there is the demand for a belt drive mod, unless it could be the same ratio as the mount when it came out of the factory and thus could be used with the handset, thus appealing to the masses.

[chrisshillito]

Malcolm,

Yes, the higher the ratio the better the "theoretical" pointing resolution. I say that because absolute positioning accuracy is a difficult thing to determine due to the fact that each stepper motor step is split into 64 microsteps and these most likely are not evenly spaced and each micro step position will apply a different level of holding torque etc.

If you go for a higher than standard ratio then you will get a reduction in the top slewing speed available - the mount will slew at what it thinks is x800 sidereal but clearly the increased ratio will slow down the movement. I can't see that this would be much of an issue though - so long as the mount gets to target it doesn't really matter how fast it gets there (unless you're doing satellite tracking).

I must confess I've taken an interest in mini lathes of late too - just out of curiosity. As you say, it is a lot of money for a lathe and the other tools (bench grinder etc) and accessories that would be required - not to mention the time that would need to be spent to relearning even the basic machining skills I once had.

With regard to handset compatibility I've got some dual USART PIC samples on order with the intention of producing a simple (EQDIR sized) plugin device that will hopefully fool the handcontroller into providing correct control (I do enjoy a getting back to my roots with a spot of embedded assembly level programming!). I'll keep the group informed if there is any progress on this front.

My pulleys and belts arrived today (48 tooth pulleys and 80 tooth belts are back in stock now at motionco if anyone else is thinking of ordering) so I'm now preparing for the strip down, re-tune and rebuild (I've already got my grease and some teflon sheet and to make new shims if needed etc).

Chris.

[malc-c]

Chris, you're a man of many talents:icon_salut:

I've dabbled with PIC programming, mainly the basics like timers, LED flashers and (with a lot of help) a 4ch pulse proportional thermostat / lighting controller for my reptiles, the prototype of which has been running for a year now. Whilst my programming mentor done the core maths behind the PID routines, the rest of it was all my own work, including the design of the PCB which I had made in China.. here's some images

Like this belt drive project, there was a lot of interest in this, but I lacked the resources to get the thing through the CE tests so I would be covered in any event of failure. Whilst as you can see every possible precaution was taken to reduce the chance of some moron opening the case and touching parts with fingers... the fact that someone could be electrocuted if I too the risk and flogged half a dozen on the net stopped me building the other 5 units.

Anyway, back on topic - I'm going to look at pricing up some "kits", work out some costs for machine time, and then see if there is enough interest in this mod so that I could at least recover the cost of my outlay for a lathe. Mind you I need to swat up on my machining skills, last time I used a lathe was in 1978

[r3i]

I'm going to look at pricing up some "kits", work out some costs for machine time, and then see if there is enough interest in this mod so that I could at least recover the cost of my outlay for a lathe.

Will you be looking into kits for the EQ6 as well as your HEQ5? There's possibly quite a few people like me who are okay with disassembly and reassembly work but lack the skills and tools for more hard core engineering. Whether there's enough to make it worth your while, we'll have to wait and see but I hope so. Wishing you well with it all.

[ncjunk]

Will you be looking into kits for the EQ6 as well as your HEQ5? There's possibly quite a few people like me who are okay with disassembly and reassembly work but lack the skills and tools for more hard core engineering. Whether there's enough to make it worth your while, we'll have to wait and see but I hope so. Wishing you well with it all.

The thread is a discussion on doing a belt mod to an EQ6 and te first post by George mentions the bits needed, how to do it and where you can possibly buy the parts pre-drilled.

It´s a very easy mod on the EQ6.

Malc is just trying to adapt it to the HEQ5 but the thread topic is for th EQ6 and I don´t think it would need a kit (I know nothing about the heq5 so couldn´t comment if a kit is usefull for that).

I should read all the previous posts before commenting...sorry...but I still dont think the eq6 needs a kit.

Edited November 9, 2011 by ncjunk

[chrisshillito]

Chris, you're a man of many talents:icon_salut:

No, I'm a man with a single talent that I apply in as many different fields as possible and at every possible opportunity

Chris.

[yesyes]

No, I'm a man with a single talent that I apply in as many different fields as possible and at every possible opportunity

Chris.

hehehehe, well said... ;-)

Being autodidactic helps in so many ways... ;-)

[r3i]

The thread is a discussion on doing a belt mod to an EQ6 and te first post by George mentions the bits needed, how to do it and where you can possibly buy the parts pre-drilled.

It´s a very easy mod on the EQ6.

Malc is just trying to adapt it to the HEQ5 but the thread topic is for th EQ6 and I don´t think it would need a kit (I know nothing about the heq5 so couldn´t comment if a kit is usefull for that).

I should read all the previous posts before commenting...sorry...but I still dont think the eq6 needs a kit.

Hi Neil,

I've been reading this thread and George's original research thread since they began.

It was my understanding that for the EQ6 mod both gears need re-boring and the worm shaft gear needs reducing in thickness by 3mm. If this is correct, then the modification to the EQ6 is more than just an assembly exercise, it requires some machine work. This is why there is an opportunity for an enterprising person to supply the belt and the gears with the machining already done to them as a kit.

Edited November 9, 2011 by r3i

[ncjunk]

Didnt mean to sound annoying in that last message so appologies for that.

One of the companies can rebore them out for a couple of pounds before sending them..hence it becomes just a put together job.

Even if you get all the base bits, i cant remember what its like in the uk. But here in spain it cost me 6 euros for a machinist down the road to bore them out.

That was why for me personally i can see no value in the kit as it wont save anything.

Are machinists that difficult to find in the uk? (now i think about it i wouldnt know where to find one i'd have to wander around a few industrial estates)

Edited November 9, 2011 by ncjunk

[r3i]

Didnt mean to sound annoying in that last message so appologies for that.

No need for apologies Neil

I was just hoping to provide encouragement for Malc in his idea to provide the bits pre-engineered as a way to fund his lathe purchase.

I'm sure you're right that it won't be difficult to source a machinist to do the work, but if someone is offering to provide a one-stop shop by both supplying and machining the parts then good on them.

This approach has already been done in other applications, for example whole kits can be bought for the EQ6 hypertune rather than having to separately source the tools, bearings, shims & grease. For sure it's not exactly rocket science to get hold of all the different parts, but some folks prefer the convenience of a single source of supply and also they have the reassurance that someone else has made sure that all the bits are the right bits.

[ncjunk]

Point taken, plus a group of people are likely to be just covering costs rather than making money.

Those hypertunes are an example of poor value, separately sourced items are so much cheaper and parts lists on this forum. ;-D

Just waiting for some clear skies to test the belt drive. Looks like it is performing similar to Georges at the moment.

Edited November 9, 2011 by ncjunk

[r3i]

Those hypertunes are an example of poor value, separately sourced items are so much cheaper and parts lists on this forum. ;-D

Just waiting for some clear skies to test the belt drive. Looks like it is performing similar to Georges at the moment.

Yes, there is indeed a hefty premium to pay in that instance for the convenience and reassurance.

Looking forward to finding out the 'scores on the doors' with your upgrade. It's been a great project to follow.

[fwm891]

r3i, There's no change to shaft dimensions.

The 12T pulley is re-bored to 5 mm, the 48T pulley to 12 mm. The 48T pulley also has 3 mm removed from its thickness.

[MG1]

One of the companies can rebore them out for a couple of pounds before sending them..hence it becomes just a put together job.

Hi Neil, I've been watching with interest and looking forward to seeing some PE data after all these have been assembled, but just out of interest...Which of the companies will rebore out before sending the parts. I quite fancy having a crack at this if I can get the machining done...(or purchase a cheap kit )

[MG1]

PS, re washers, does anyone have a source for teflon sheet between 0.25 and 0.5mm thick?

[r3i]

r3i, There's no change to shaft dimensions.

The 12T pulley is re-bored to 5 mm, the 48T pulley to 12 mm. The 48T pulley also has 3 mm removed from its thickness.

Hi Francis,

Thanks for that. I did understand the re-boring and thickness reduction was the extent of the machining required, but such modifications are beyond my skills, which is why I was interested in Malc's idea. And I think it would be nice to the see the job go to a fellow SGL member.

[ncjunk]

George gave this link but i haven't tried them, my machinist was a couple of quid cheaper.

http://www.hpcgears.com/mods.htm

If the teflon sheets are for a hypertune then there is a guy in the states that will send you a pack of teflon washers for 13 dollars enough to do a tune up...i never looked into getting the sheets. His contact details are on astrobaby website in the hypertuning section.

I bought two sets from him last week.

Edited November 9, 2011 by ncjunk

[fwm891]

For those looking at small lathes have a look here: Chester Machine Tools - Machine Tools and Accessories and their small lathes - Conquest series. I have dealt with Chester before but no affiliations etc etc etc...

As nearly all threads you need to cut for filters, adapters etc are metric, make sure your getting a metric version - some companies are offering Imperial versions at reduced prices but you will then need Imperial/metric conversion gearing - probably more expensive than the metric lathe to begin with...

[ncjunk]

Hi Neil, I've been watching with interest and looking forward to seeing some PE data after all these have been assembled, but just out of interest...Which of the companies will rebore out before sending the parts. I quite fancy having a crack at this if I can get the machining done...(or purchase a cheap kit )

My gut feeling is that the peak to peak PE has improved slightly. The main benifit is that my PE before didn't seem to form a nice repeatable pattern. I did a quick check the other night and got a repeating partern similar to Georges he posted here.

Also the guiding is coping better so i think that with PE correction enabled my mount will be guiding much better than before the mod.

It depends on your mount, if its working fine for what you want then i wouldn't touch it.

I got a test shot of m76 at fl1800 on the c11 and the stars were looking a lot better.

[malc-c]

The thread is a discussion on doing a belt mod to an EQ6

Malc is just trying to adapt it to the HEQ5 but the thread topic is for th EQ6 and I don´t think it would need a kit (I know nothing about the heq5 so couldn´t comment if a kit is usefull for that).

I should read all the previous posts before commenting...sorry...but I still dont think the eq6 needs a kit.

Neil, sorry for hi-jacking this thread... I was going to post the question regarding different ratios on the HEQ5 thread I started, but then Chris had outlined all the settings and aspects of different ratios in this thread...

As for kits..the one thing I've found is it can be either difficult to find a decent machinist that will bore out and turn them down to the correct size properly (so they don't wobble or rub), and /or find a machinist that doesn't charge the earth to do the work (I was charge £40 which was more than I paid for the parts). The other factor for looking at "kits" is that purchasing in bulk reduces the cost of the parts, thus "hopefully" makes it cheaper for other members. It also make for a convenient solution for other members who haven't got the time to get the parts machined.

I'm sure if I do end up persuading the boss that I need this lathe, and then have the capital to bulk buy the pulleys etc then I'll also offer them for EQ6 owners.

Having said that, I'm sure there are other members with access to or own lathes etc and could well do the same... It would certainly save me a lot of bother and the expense of a lather and all the gubbins that go with them

[malc-c]

For those looking at small lathes have a look here: Chester Machine Tools - Machine Tools and Accessories and their small lathes - Conquest series. I have dealt with Chester before but no affiliations etc etc etc...

As nearly all threads you need to cut for filters, adapters etc are metric, make sure your getting a metric version - some companies are offering Imperial versions at reduced prices but you will then need Imperial/metric conversion gearing - probably more expensive than the metric lathe to begin with...

Thanks for the link... I must admit, from my limited research it's almost as mind boggling as buying a scope for the first time

Seems most people recommend a 4" self-centering chuck, rather than a 3", and given that these pulleys are typically 40mm diameter a 4" would give better handling... but they typically cost more

What's at the back of my mind is what would I use it for after I've done this project... I'm not into building miniature V8 engines etc.. and I can't think of many astro applications either..

[ncjunk]

40 pounds? Crikey! My machinist is cheap at 6€ although he did moan at me at the amount the small pully had to be bored out by.

It's Georges thread and i'm sure we are not too off topic!

Over hear there are still loads of small land owners with lots of equipement to maintain hence lots of machinists around the place. One man and his machines on a street corner, you dont get that in the uk anymore.