90° micro gear box

[Julia]

I need to change drive through 90°, but have a really small space to do it in, a cube of approximately 4mm on each side. 

 

Does anyone know if anyone makes gear boxes small enough for this? It's not got much torque to worry about, but it does need to be nice and compact.

 

Cheers

 

J

[nick_bastable]

I need to change drive through 90°, but have a really small space to do it in, a cube of approximately 4mm on each side. 

 

Does anyone know if anyone makes gear boxes small enough for this? It's not got much torque to worry about, but it does need to be nice and compact.

 

Cheers

 

J

how small do you need check out http://shop.kkpmo.com/index.php?cat=c336_7mm-Geared-DC-Motors-7mm-Geared-DC-Motors-336.html

 

 

 

Nick

[bertiedog]

Small 1:1 right angle gearboxes are as rare as hens teeth, however there are different types and rearranging things may help

1. The classic type is where the shaft input is in line with the cross shaft, a contrate gear or crown wheel on the cross shaft, with a pinion on the input, common on slot cars. The type can be 1:1 to any ratio, but the 1:1 and low ratios means a big pinion wheel with a high enough tooth count to work smoothly. A very small toothed 1:1 could be fitted into many small models, and your 4mm limit restricts the types to moulded plastic, as metal would be complex to machine that small. Many specialist mechanisms such as digital focus motors have these micro gears inside, but they are custom made for the job, and not sold separately.
2. The second type is the crossed helical gear, with the input shaft separated from the output by the total of each gears pitch, in other words not in line. They range from 1:1 upwards. A 1:1 pair would fit a 4x8 area, but in practice such small helicals are rarely made. Again specific mechanisms may have them in moulded form
3. The third type is well known, the worm and gear, but low ratios are difficult to arrange due to minimum practical tooth counts and 10:1 is usually the min, although smaller are made in precision form.

Most gear factors do not make such small gears as model railway users require,  but the online supplier in the earlier post does list small worm and gear, and some helical types.

 

Do not forget there are other pros and cons, worm gears are quiet, contrate are noisy, and helical gears generate side thrust, considerable side thrust, which means attention to the bearings is needed, as the output shaft must have no side play.

 

A pot luck approach is to buy the cheap motors and moulded gearboxes from ebay, there were made for focusing mechanisms for cameras, and as they are going out of use with linear motors taking over, they are being sold off.The gears are tiny and usually have two start worms of tiny size, but if these are used you will face redrilling them or other alteration and this will need a lathe. Some times your in luck, and the motor can be used as well, but they are tiny motors.

 

The next step are the complete mechanisms as per the previous posting's supplier, a motor and gear set complete and ready to go. They go from pretty small to normal railway sizes.

 

The last approach is to go to a gear maker and have custom gears made......cost may be prohibitive. You could try Ultrascale, they may have stock items that fit or have stock from other projects that would fit.

 

Some further information on your exact requirements may help spot what is needed.

Hope this helps.

 

Stephen.

[Julia]

Thanks all for the replies, 

 

I have ordered a 10:1 gear box from the site linked to by nick_bastable. It's small enough for what I need (5.4mm x 4.6mm x 4mm). Now I just need to workout the rest of the mechanism to connect it up to a servo to do what I want. 

 

Cheers

 

J