Model Boat Mayhem
Mess Deck: General Section => Model Boating => Topic started by: Lt. Raen on June 08, 2011, 07:02:22 am
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Hi there
I have been searching for a 2:1 belt drive reduction system similar to the one bluebird used on his cervia build
However I have had no luck finding one, i could purchase the parts individually and attempt to build the system myself
but i would prefer to buy an all in 1 system
If anyone knows a supplier i could get one from that would be greatly appreciated
Oh an di live in sydney Australia so a supplier in Aus would be even better :-))
Cheers
Tim
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have you tried www.floataboat.com.au its possibly easier to contact them at the address supplied on their website. couldnt see anything listed but i think they would have something or be able toget it. rhonda is very good with email replies and they provide an excellent service.
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Hi there hopeitfloats, i contacted float a boat today and had no luck, they wish
they had a belt driven reduction unit but they dont stock it and there only
suggestion was to contact MFA in the UK.
After contacting MFA it appears that they only have a reduction system for much
larger motors.
I stumbled on this site http://www.smallparts.com.au/ and her sister site
http://www.hobbyparts.com.au/ which looks promising, and even if they
dont make what i want i can definitely get all the parts i need from there.
Cheers
Tim
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Hi there
Tim, very sorry I missed this posting, if it hadnt been for Dicky rattling me cage I would have missed it. As you now know MFA do no longer produce this gearbox. However, I do know of a shop local to me who had a few in stock. If you are interested let me know and I will contact them for you to see if they will post one out to Australia for you and I can pass you all the information about the shop. I will phone the shop tomorrow and let you know.
aye
john
bluebird
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Thankyou Bluebird, that would be greatly appreciated.
If they dont have any left i will bite the bullet and construct one of my own
which might prove interesting %%
I will be starting a new thread of my Cervia build as it gets under way in a
coulpe of weeks. As soon as uni exmas are over and I have some spare time.
Thanks once again
Tim
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i'm surprised floataboat couldnt help but sounds like you may be on to something. thanks for listing those sites too. have saved in myfavourites list. i can see me using them in the future. craig
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google mfa como, they have different size belts and gears, quite cheap, dead easy to change the ratio by changing the gears, Just ordered some new ones last week, I use them in my Huntsman and fireboat :-)) Here is a video in operation,
http://www.youtube.com/watch?v=e0vJGoCM8vM
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For us non techs, could someone explain in simple terms,
1.What is gearing up
2.How you gear up
3.Result of gearing up
4.What is gearing down
5.How you gear down
6.Result of gearing down
(Googgling didn't work for me).
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think of direct drive as driving a powerful car only in first gear, loads of revs, no go. Take my pic above, if it was direct drive, that would be the result. so, my shaft gear is 30teeth, and in that pic motor gear is 12 teeth, approx 2.5:1 (dont have a calculator to hand), so, whilst acceleration will be slower,(starting your car in say 3rd gear, slow off the mark, but once going faster than 1st gear) its like changing gear to 4th, better top speed. If I increase to 14 teeth, its now closer to direct drive of 1:1, giving better acceleration, but reduced top speed. If i reduce to 11teeth motor gear, in theory it will be slower off the mark, but better top speed again.
However there are some variables, the prop, and motor power, in my case kv rating as its brushless. That motor on direct drive, or 1:1 ratio will run too fast, resulting in heat and short run time, and big amp draw sucking the batteries down. If I sail on a small lake, then I want acceleration, top speed isnt important. If its a big lake its nice to stretch the boats legs, and go for top speed, whilst all the time trying to maximise run time and efficiency. For me, I enjoy testing and meddling, I have a data logger and gps for the boat, so can really drill down to the facts and figures. Brushless and lipo technology is quite an unknown thing in a large scale boat so its been a lot of trial and error as there is very little reference, the gearbox has enabled me to really achieve the impossible with a 7kg boat, 22mph and 20 mins running, hope that helps, there is a lot more info in the full build detailed here on mayhem :-))
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Not quite Red...
I will keep it simple with a gear ratio of 2:1, gears of 10 teeth & 20 teeth....
To gear UP the 20 tooth gear will go on the motor and the 10 tooth gear on the final shaft. This has the effect of reducing the available torque produced by the motor (slower to spin up to top speed) but will double the motor revolutions at the shaft (i.e. motor speed 1000 RPM shaft speed 2000 RPM) Imagine trying to pull away in your car in top gear.
Gearing DOWN the 10 tooth gear will go on the motor and the 20 tooth on the shaft. This has the effect of multiplying the available torque produced by the motor (faster to spin up to top speed) but will HALVE the motor revolutions at the shaft (i.e. motor speed 1000 RPM shaft speed 500 RPM) You are now pulling away in first gear....
Mark. (Ex car mechanic!!)
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Also see:
http://science.howstuffworks.com/transport/engines-equipment/gear-ratio.htm
http://en.wikipedia.org/wiki/Gear_ratio
http://en.wikipedia.org/wiki/Pulley
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:o ...whilst it is not an issue with toothed belt drives........mechanical gearing vis....even number to an even number of teeth should be avoided
The simple point is such even ratio's provide that the same tooth will engage to the same tooth on a ratio given by the ratio %% & this creates WEAR irrespective of lubrication
An ideal scenario is one gear with an even number of teeth mated to a gear of uneven number of teeth vis....12 to 25 or 11 to 20.... O0 .....Derek
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Try http://www.hpcgears.com/downloads.htm they supply gears belts etc
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Wow some great info being offered up here :-)
@red181 I contacted MFA como drills the other day and they no longer make anything suitable for the
540 motor I am planning on utilising. They make a toothed belt system for 800 and 850 sized motors
(see here http://www.mfacomodrills.com/gearboxes/960d_series.html ) however i think this will be too
large for my intended usage.
I am still waiting on a reply from Bluebirds source and hope to here from them on moday.
However, that said i would be interested in learning how to create a mounting bracket for a motor and
belt system. Im thinking a simple right angle bracket for the motor and a short shaft running on 2
bearings would probably be sufficient ... hmm perhaps a quick imagine to help visualize what i mean:
(http://i682.photobucket.com/albums/vv189/Raen_09/ST%20Cervia/2to1timingbeltreductiongearbox.png)
Or is there a simpler way of doing this?
Anyway tell us how you would do it :-)
Thanks
Tim
Tim
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Firstly may I address Derek's quote on uneven gear running on an even gear being the ideal.
In all my years working in the engineering industry with 10 years in a gear box manufacturing company this is the first time that I have heard such a statement.
If gears are cut properly irrespective of numbers will wear equally and any 2- surfaces mating and transferring power will wear.
In a high speed gear train an unequal toothed gear would have to be dynamically balanced and secondly if a gear wheel had to be changed in another country, not the country of manufacture it could be difficult to get an uneven gear wheel, so most manufactures stick to even gears .
But I digress we are talking about toy gear boxes here which can be run a speeds in excess off 30,000 rpm with no ill effect on uneven gears.
TIM,
You have been given the link to H.P.C. gears who have very reasonable costs in their DELRIN gear range.
I used them for a brushless set up to gear a 3,600 kv motor ( multiply this by the voltage to give out put r.p.m. I run on 8.4 v) down 2/1 by drilling and tapping for a hex grub screw thro' the boss onto the shaft with great success, if you can't get the exact bore required it's an easy job to drill out to suit your shaft .
Here is a pic of the simple set up installed in a BRAVE BORDERER
George.
(http://s3.postimage.org/kk5p12pw/Brushless_geared_motor_1.jpg) (http://postimage.org/image/kk5p12pw/)
(http://s3.postimage.org/kkann478/Brushless_geared_motor_2.jpg) (http://postimage.org/image/kkann478/)
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what's it like noise wise. i have never been able to run a geared motor that is quiet.
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Yes definitely a lot of reading and references for me to follow up. :-)) :-))
Got the drift about car gears etc, but in a model boat there is no gearbox as such, or gear changing. O0 O0
With direct drive what goes in comes out namely 1 to 1, the speed is regulated by the electronic speed controller (accelerator).
As we don't change gears in boats (models), still having a problem with why you would need to gear up or gear down the motor output, if it works OK as a direct drive connection.
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hi ya Tim
If you dont get a reply from the link I put on by Monday, let me know - I will give them a ring and we will sort something out for definite that is if you definitely want to go for MFA belt driven gear box. 0n a sidenote, producing and making your own belt drive gear box is a good idea, but, like most things - there are pros and cons with using beltdrive and also as an alternative geardrive. Beltdrive gearboxes tend to be a bit quieter in running they can be a bit of a pig to set up - owing to trying to keep the belt to run true between the two pulleys. Sometimes you can overcome this by having flanges fitted on the pulleys but, even with these in worse case scenarios the belt can over-ride and jump over the top and cause uneven wear to the belt - whereas gear drives tend to be more forgiving in alignment in this field, they do tend to be more noisy though, even with the best meshed gears. The drawing you have put on here I think is ideal for what you require.
As another sidenote - if you send a pm to billyruffin on this forum - Billy built the Cervia tug but he used direct drive - I am not sure what sized prop and motor he used - he will tell you - if you want to go that way.
aye
john
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...still having a problem with why you would need to gear up or gear down the motor output, if it works OK as a direct drive connection.
The point is, you should use gearing when a motor doesn't work OK in a direct drive set-up. Here's an equation:
Power = torque * angular velocity
Any motor has an angular velocity (revs) and a particular torque at the point where it's working most efficiently.
Suppose I stuck on a large diameter, steeply pitched prop to a motor - a prop difficult to turn, and likely to cavitate if driven at high revs. In order to maintain motor efficiency and efficiency at the prop, I would need to gear down the output shaft - I could have an "ideal" 10000 revs at the shaft, reduced to 2000 at the prop. You can see from the equation this reduction would increase the torque five-fold.
Andy
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However, that said i would be interested in learning how to create a mounting bracket for a motor and
belt system. Im thinking a simple right angle bracket for the motor and a short shaft running on 2
bearings would probably be sufficient
So have you looked at http://www.minibearings.com.au/technical/timing/ (http://www.minibearings.com.au/technical/timing/)
Did you note the key word in the company name....?
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@Bluebird Thanks, I will let you know if I dont hear from them, as I feel a system that is already set up will be much
simpler for me than creating my own box. Although the experience would do me good. O0
@Ooyah/2 I too would be interested in the noise produced by your gear system there. Also how is the lower gear
held into position? is there a small shaft running on a bearing? I cant see anything from the photos.
@RaaArtyGunner In this particular case I want the drive reduction because the motor will eventually be used in a
model of a Tug (If i ever finish it %% ). The 540J motor I have is quite a fast motor and efficiently runs at fairly
high revs. However, the prop will only need to run at relaively low revs to be efficient and produce scale speeds.
By using A 2:1 belt reduction I hope to maintain motor efficiency and keep scale speeds. I think dreadnought72
sums it up fairly well ;) :-))
@BJ Do not fear I have that site bookmarked and have perused it will, the belt, 2 pulleys and bearings would add
up to about $40aus + approx $10aus for postage, as Queensland is a little far from Sydney for pick up %% plus I
would then need to build a mount for the engine and ensure correct allignment. However as I said I am willing to
make my own drive belt system if I had too, but thanks too Bluebird it looks like I wont.
Thanks for the comments and info its all great
Tim
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thanks for supplying that explanation Dread! :-))I struggled at 1.00am getting it that simple :}, but thats the basis really of gearing, in my application pictured, motor was running too hot, run time was very short, and the batteries where being drained by a high amp draw as 1:1 or direct drive, that motor is actually too high kv, didn't know it at the time as brushless info in my sort of boats was pretty much unavailable two years ago, just now in the process of fitting a lower kv motor which should improve things.
I think, MFA supply the gears pre bored at 4mm, so if your motor is a smaller shaft, perhaps you could sleeve the gear? mine are all 5mm and 6mm motor shafts, so I don't have that problem. The mount was custom made by a good friend, I am very lucky!, so maybe you will need to fabricate your own?
Dead right Bluebird, it took a while to get the gears to be lined up correct, when I remove and replace, I use a straight edge over both, its amazing how much speed is lost, and how much the amp draw increases if they are not lined up correctly, or the belt is too tight (I use eagle tree data logger to record all the runs). If you see the video of the belt drive, it doesn't walk much on the gears, but I do use gears with flanges for the reason Bluebird has mentioned.
Mark,don't really see the relevance with your post mate, I never mentioned gearing up, or down, {:-{ just the principles of gearing in general, and the actual findings of what happened to me. If I can share my actual experiences to help people save time and money, then I believe thats what the forum is about, it took me 8 months to arrive at that short post in terms of the experience of changing gear ratios, and of course props, I do understand what you are talking about, but it was 1.00am when I posted!
Lt, the noise is fantastic, and can be best compared with a turbine, but I think it was just luck getting that, a combination of the alloy mount, motor, and the motor area resonating like a sound box :-))
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Mark,don't really see the relevance with your post mate
I won't bother next time then!!!
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@Ooyah/2 I too would be interested in the noise produced by your gear system there. Also how is the lower gear
held into position? is there a small shaft running on a bearing? I cant see anything from the photos.
Hi Guys.
I believe in making things a simple as possible and the gear train shown has no bottom lay shaft or any other than what can be seen in the pic, the large bottom gear is fixed on to the main shaft with no support and works well, very simple and easy to make.
I originally tried a straight 1/1 drive with a 32 mm carbon fibre prop, this was very noisy with prop cavitation and a very poor run time.
On changing to the 2/1 gear drive I stepped up to a 45mm prop and the boat was faster and had a longer run time and it had a very significant reduction in noise,in fact with the top super structure on you can barely here any noise.
BRAVE BORDERER is 36" long and with the present set up is very fast and quiet running in 7 Sub "c" x 3700 battery when powered by 10 Sub "C" battery it's too fast.
I don't have much experience with Elec motors but years ago I built a CERVIA to 3/8" scale and had a straight drive from a bus heater motor and constantly burned it out, fortunately a mate had a scrap yard and motors were in abundance.
On making 2/1 reduction pulleys using a Hoover 1/4" dia drive belt I was able to use a 3.75" x 4 blade prop and this cured the burn out.
I think that a 504 motor on a straight drive will have the same effect of burn out and a 2/1 reduction will allow you to fit a larger more scale prop.
My CERVIA is now powered by a D10 steam engine with the same prop and can tow a small dingy with 2- bodies in it
In conclusion RED181 and the others have it correct and have explained it better than I can so reduce the out put and gain more torque and running time..
George.
(http://s2.postimage.org/2a2vve59g/BRAVE_3.jpg) (http://postimage.org/image/2a2vve59g/)
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Hl fellow members. M F A no longer make the Olympus belt drive system but I bought four of them today from Model Slipway while attending the Northern Model Boat show at Doncaster. The cost of these units is £14 and the coupling for these units from S H G are priced at around £6. I think Slipway had only six remaining at the end of the show. I have one of these units in a semi scale tug and with a M F A torpedo 500 motor running, it draws less than 3 amps during running. I hope this information helps. Model Slipway can be contacted on [email protected]
Stan :-)) :-)) :-)) :-))
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Hullo George......who says .... "In all my years working in the engineering industry with 10 years in a gear box manufacturing company this is the first time that I have heard such a statement" .....odd to even gearing...... :o
I did not invent this...but in my basic grounding 30 something ++ years ago.... :embarrassed: in the 'history of mechanical computers for train & elevation of gun mounts from WW1 ' included the fact that gearing was odd to even ratio + included antibacklash compensation...remember we are only talking straight cut bronze on bronze gearing of approx 3/4" to 1 1/4" to 2 1/2" diameter
The same engineering protocol relates to roller chain pinions.........Derek
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Heres a couple of links that may be able to help you out
http://www.econobelt.com/
I found them to be much cheaper including shipping than local suppliers if your willing to trawl through it
[email protected]
John Darke of Darke Horse Model Supplies
An all round good guy that will be able to advise and supply what you require.
I'm with Derek on the number of teeth, just look at the gear ratios of cars O0 (but for our modest requirements it will be of little matter)
Gearing matches the prop to the motor, electric motors like to spin at high RPM for efficiency, but props like low LRPM to reduce cavitation. When a motor is forced to spin at lower than optimal RPM it draws more current and gets hot.
Nick
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Hi,Derek,
Thanks for the info on gearing and as I have never studied the principle of gearing I bow to your knowledge of Naval Gearing and I stand corrected.
When we designed heavy industrial gear boxes odd to even teeth were never a consideration but I accept what you say.
However we digress again from the original inquiry on a 2/1 reduction for a model boat and in my opinion it doesn't matter if the teeth are odd or even.
The Delrin gears in my boat , much to my surprise are still churning away without any sine of wear and very quiet in running, are cheap and easily obtainable .
I must add that I didn't think a grub screw tapped into the Delrin boss would hold, I always think steel, it must be that on drilling the 4mm hole for the shaft that when drilled it's a tight push fit on the shaft which must add to the grub screw grip.
I am sure that there must be a supplier in OZ where Delrin gears can be had to make a simple gear box so a quick search with Google may turn up a supplier.
George.
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@stan out of interest I contacted model slipway anmd recieved this reply "Sorry, we are not a model shop, we manufacture and sell products suitable for Model Slipway and Model Slipway kits." So doesnt look like they will be of any help.
@bluebird PM sent
Tim
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Just a quick update for anyone interested,
I have ordered the Belt drive and now avidly await its arrival on our golden shores %%
Regards,
Tim
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HOPEITFLOATS.
Here is a link to my Brave Borderer on You-Tube, running on 2 x 7 Sub 'C' cell packs x 3700 amp in parallel (http://www.youtube.com/watch?v=c2FxmJ20mkk&feature=mfu_in_order&list=UL ) the motor is a brushless 3750 kv
It's a bit of a whine but not unacceptable and don't forget Lt Raen will not be running such a high reving motor.
This set up has been very successful and a cheap way to make a 2/1 reduction G/Box.
George.
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I have used a pulley reduction system in a number of my models with very good results. I use nitrile O-rings as the belts, they are cheap, very quiet, and last quite a long time. In early models I used a single belt system, but now generally use a double belt set up for extra grip and reliability. I turn the pulleys on my lathe using aluminium rod of suitable diameter.
I have attached a photo of the single belt set up in use on my Billing "Nordkap", and another of a twin motor set up in a pusher tug. This has since been changed to a double belt arrangement.
Peter.