Outboard DC motor ballast

[johnlncstr]

Hi Guys

I have almost completed an outboard motor mod to my Rock TT using a floppy disc drive motor. I have built the unit into a diecast aluminium box 188mm x 120mm x 55mm the box size works out almost ideal mechanically and cosmetically. However I intended to use lead shot as a ballast medium but it has become obvious that this is not such a good idea due to lead dust contaminating the pc boards with disastrous affects. I am hoping that someone out there knows of a granulated material that that is nonconductive, heavy enough to replace lead as a ballast material and large enough to not get into the bearing. I could seal the compartment but this would make remedial repair work impossible. Any Ideas fellers.

Regards
John Lancaster.

Put the lead into small, sealed plastic bags and pack your box with a few of those?

[johnlncstr]

Lord

Thanks for the answer, I feel a right prat the only excuse I can make is I was standing too close to the job. Cheers.
regards
John l

[Shane]

Hi John,
I've been thinking about using one of these motors for a TT project. Can you give me some idea how powerful yours is with respect to the Rock's original motor? Also, are you able to vary the speed, or is this set by the motor's own electronics?
Thanks,
Shane.

[JerryT]

I use very small lead shot (liquid lead) for ballasting model railway rolling stock. Dilute PVA glue holds it in place well as long as you apply sufficient glue and allow it to dry thoroughly. This is a useful technique for odd shaped containers and for getting the maiximum mass in the space available.

What it does prevent is the shot moving and dissipating vibrational energy through friction - but lead is actually quite a good libricant and these losses will be small once the shot become polished.

Jerry

[Greg.]

Hi John,

Because of the environmental concerns regarding lead shot (fishing and shooting etc), it is hard to source. A couple of years ago I tried to get it to fill the cavities inside some speaker stands. What I ended up using was lead swarf salvaged from the floor of a lead fabricators workshop. In the course of cutting long lengths of lead, small chippings are produced. This way I filled two large stands for a fiver into the companies tea fund.

Best wishes,

Greg

[Rob042]

John
keep us updated on this floppy motor mod - pictures if you have them.

Rob

[johnlncstr]

Shane
Glad you got the reply although it went all round the houses my fault. The reasoning behind choosing the floppy disc is the motors are remarkably poweful for their size well able to propel the platter even heavy ones (although I propose giving it a hand with a slight push when starting ). Also they are very compact. The speed control parameters set into the circuitry are faced with the same problems of speed control as a TT and the circuitry is quite sophistcated well able to cope (leastways that is the thinking ). The motors on the airplane webb are obviously powerful enough but I think you will have considerable trouble getting or making a controller sensitive enough to work to the limits required.I have a Maxon motor depot close to me and I investigated them first and although they could supply a DC motor of good quality for around £80.00 using their power/control system worked out at about £750.00 on top and they were uncertain of its performance at such low revs.Hence the floppy even if it doesnt work I have only spent about £30.00 and I can go back to my old A/C motor.The power source I am using is made by ETL /Amplus China Mod No 0179 and is controlled by slotting in different resisters to arrive at the required voltage, the local instrument bashers use them and they like them for stable voltage particulally used in conjunction with my mains cleaner. That cost £12.50. The biggest problem you will have is getting someone to turn you up a pulley, proffesional shops dont like it because of the time consuming fiddling but contact with your local model makers will normally provide an interested party happy to try something different. I found them knowledgable practical engineers capable of thinking outside the box and if you can stand the ragging about stone age technologies, great company. You should see some of the beutiful working steamers they make, I could sit and look at them for hours,the detail is incredible.I will try to remamber to take some photos during rhe final build and post them,any further questions I will do my best to answer.

Regards

John L

[Shane]

John,
many thanks, you have been a veritable mine of information! I think I shall have a bash at the floppy drive route. I know an excellent small engineer locally (literally, he stands about 4' 8"....), so a pulley shouldn't be too problematic.
I'm intrigued at the idea of steam enthusiasts ragging idler drives as stone age technology. Phrases involving pots and kettles come to mind!

[johnlncstr]

Shane

After checking my posts I have just realised I did not give you the most important piece of info . If you go to www.audioorigami.co.uk you will see photos and a blow by blow account of the development of this idea, However due to the variety of floppy disc circuits whilst the plug terminations remain the same the internal wiring may not, eg the microswitches so proceed with caution and be ready to make your own modifications as you go. Be careful if you use superglue to seal the bottom of the bearing it only needs a very very small amount too much and it will impede the shaft and if the whole bell is raised in relation to the windings the speed increases but torque reduces. A lot of these problems are not so much due to a failure of design but due to an eagerness to get the thing up and running and share his idea with the diy community. Practice makes perfect. Whilst I am on let me say thanks for all the ideas on ballasting I have a number avenues to choose now. Thanks all.

Regards

John Lancaster