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Rhino Fire replacement motors
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Ratman99UK
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Joined: 04 Apr 2017
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Post Rhino Fire replacement motors Reply with quote
Hi all.
I just got a rhino fire from Shpock for £30. Too good to be true and it was.

The pusher motor was burnt out which I've replaced with a stock stryfe Motor for now. I have a MTB rhino on the way (I'm using a 3s so 12v motor is needed)

The two fly wheel Motors both ran but were mega slow. I mean darts stuck between them slow (using stock d battery's at this point)
I opened the motors up and cleaned the brushes (they were black) which has resolved the problem.
But ideally I'd like to replace the two motors. The problem I have is the motor has a drive shaft on both the front and back (for each sides barrel). Iv had a look on eBay and while I can find 130 motors with dual shafts they are no where near long enough. The shaft needs to stick out 13mm on each side of the motor.

Does anyone know where I can find such a motor?

Thanks

Ratman99UK
Sat Jun 03, 2017 1:51 pm View user's profile Send private message
SSGT
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Post Reply with quote
There isn't much out there I'm afraid - the few dual shaft motors that have long enough shafts likely don't have appropriate motor winds to yield usable speeds at 2S or 3S.

As far as I can see there are a few options. The first is to use the stock motors with a 3S pack. If you do want to use the stock motors for any length of time (and especially if you do end up using a 3S pack) it'd be a very good idea to buy a cheap pair of FC130 motors and cannibalise them for their carbon brush packs as per this post. The standard stamped copper brushes will not last long, especially at the higher voltages/currents that come with using a higher voltage pack, and you don't want to wait until they fail before replacing them as they often cause a fair bit of damage to the commutator as they wear.

Something that might allow you to use the existing flywheels with a shorter shaft motor is using a bolt-on universal mounting hub to mount the flywheel to the shaft. Since this relies on a grub screw rather than an interference fit between shaft and flywheel you don't need to press the flywheel as far onto the shaft. Unfortunately they don't seem to come with a shaft size as small as 2mm but you might be able to use a 3mm or 4mm hub with a sleeve reducer or a 5mm hub using the existing hub of the flywheel as a sleeve reducer (for the former you'd probably have to remove the flywheel hub completely whilst with the latter you'd need only to cut away enough of the existing hub to allow the grub screw to pass through). The downside of using sleeve reducers is that it adds potential points of movement and/or eccentricity between flywheel and shaft and the additional mass of the aluminium hub will also increase the moment of inertia thereby increasing the time taken for the flywheels to spin-up.

A more elegant solution might be to use different flywheels entirely. Whilst standard flywheels may not work well with shorter shaft motors in a Rhino Fire it's possible that the flywheels intended for the Demolisher (either Worker flywheels or standard Demolisher flywheels) might. These flywheels are physically wider and, in the case of the Worker replacements (see Super Gripper's post), feature an offset in the concave profile towards the open end of the flywheel which would potentially allow you to press the flywheels further onto the motor shaft vs standard width flywheels thereby negating the problem.

If you can modify the flywheels or use Demolisher flywheels such that you can use shorter shaft motors then that would allow you to use something like a NSR Shark 40 which is a pretty good flywheel motor and was very popular back when the RS was first released (even though that meant cutting off the additional shaft at the endbell - it produces slightly less torque than a Rhino but significantly more than most, if not all, stock motors). The Shark 30 is also an option but might be a little on the slow side especially for Worker wheels.

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Last edited by SSGT on Sun Jun 04, 2017 6:25 pm; edited 1 time in total
Sat Jun 03, 2017 3:27 pm View user's profile Send private message
Ratman99UK
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Joined: 04 Apr 2017
Posts: 94
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Post Reply with quote
hi ssgt

thanks for your help.

I just got back from a Nerf war so I will read this indepth tommorow.

Regards

Ratman99UK


EDIT:

I tried it again today. The flywheels are back to moving too slow to push the darts.
I'm afraid they need replacing Sad

I can't find any of the motors with the carbon bruses on eBay to swap them out.

Iv found these: Look at this on eBay  http://www.ebay.com/itm/112267951868

Iv messaged the seller to see what length the dual shafts are. they are bit fast 39k but useable.

They only idea, I have is to use those with different flywheels like you suggested.

Ratman99UK

EDIT

Please don't double post, edit your previous post instead. If you need to bump the thread, copy the contents of the previous post, delete that post, and paste it into a new one along with the new content. Thanks -SSGT


Sun Jun 04, 2017 9:10 pm View user's profile Send private message
SSGT
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Post Reply with quote
Funnily enough the motors you've linked are FC130s and have carbon brushes, although they are a bit expensive to buy just for their brushes. Most of these, and some of these (check the listing for images of the brushes - sometimes they claim to have carbon brushes but actually don't), would be suitable donor motors as long as the existing brushes aren't already worn to the point where they'll have caused damage to the commutator.

Are you 100% sure that it's the motors and not something else like a poor connection or the D cells at fault? They would likely have recovered slightly in the time taken to open up the endbells and clean the brushgear and that may have made it seem like cleaning the brushes solved the problem. Also, unlike carbon brushes which are self-lubricating, stamped copper brushes tend to need something in the way of lubricant which was likely removed during cleaning.  That said, even if the battery/connection/lack of lube is the problem, I'd still recommend upgrading the brushes or the motors themselves - sheet copper brushes are a cost-cutting exercise pure and simple.

As long as the listed 39kRPM is the no-load speed at 12V (therefore closer to 36kRPM at 11.1V) then those Rush 39Ks linked would probably make fairly decent flywheel motors. The shafts still only look about as long as those of the Sharks though (maybe around 9mm long) so, if you can get hold of them, I'd still probably still recommend Shark 40K motors over the Rush 39Ks. The Sharks should produce almost 10% more torque, are a known quantity and should work out significantly cheaper with faster delivery if you can purchase them from a UK seller. They are a little faster (37kRPM at 11.1V), which isn't necessarily a good thing, but that will allow for additional headroom for the speed to drop under load which might be useful with a full-auto dual-barrel setup (normally I'd recommend 180s for a full-auto but that obviously isn't possible with the Rhino Fire). Topslotsntrains are currently out of stock of bare motors but, if you can't wait for them to restock, they do have Sharks with pinion gears for slightly more (still slightly cheaper than a pair of Rush 39Ks from the US) if you don't mind removing them although you do have to take a bit of care with that (if you don't have a pinion puller the best way IMO is either to clamp the pinion and use a drift on the shaft or lightly heat the pinion and lift if off - you want to avoid putting too much axial load on the bearing/bushing).

If the Shark and Rush motors have 9mm long shafts, and the Rhino Fire stock motors have a shaft length of around 13mm, then the 3-4mm wider profile of the Demolisher wheels should be able to make up the difference.

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Sun Jun 04, 2017 11:32 pm View user's profile Send private message
Ratman99UK
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Joined: 04 Apr 2017
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Post Reply with quote
Hi SSGT


The flywheels when tested was on an s3, depending on what motors I end up getting I might have to switch to a s2. I also resolderd them into the PCB to check for dry solder joints

This is a video i took of it Saturday working after the cleaning (ignore my ramblings):

https://youtu.be/Z7ligjRVkec

So to recap, thinking i need to buy:

2x http://www.topslotsntrains.com/to...asp?ref=Nsr-3005-SHARK-MOTOR-40K-!-RPM-UNIVERSAL-&id=3221&manufacturer=%27NSR%27

when in stock

4x http://www.ebay.co.uk/itm/1223274...amp;ssPageName=STRK%3AMEBIDX%3AIT

The above will allow me to increase the length of the shafts to let me use worker flywheels.

------EDIT:-------

scrap the Couplers, I managed to find the worker Demolisher flywheels. Got to wait for them to come from Australia though Smile

Ratman99UK
Mon Jun 05, 2017 8:24 am View user's profile Send private message
old_man_nerf
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Post Reply with quote
How many demo flywheels do you need? I have a set of workers currently sitting unused....

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Mon Jun 05, 2017 1:44 pm View user's profile Send private message Visit poster's website
SSGT
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Post Reply with quote
Do you mean a 3S pack? If so have you performed any other modifications? A 3S pack with an otherwise standard loom will likely increase the current draw enough to trip the PTC fuse. There is usually a separate PTC fuse for the flywheels and the pusher (often with a third "whole blaster" PTC fuse) so it is possible for one to trip and not the other leaving the pusher operational but not the flywheels. Like dying D cells this is something that, after being left for a while, would suddenly appear to start working again.

Those are the motors but, before you do anything else, could you measure the width of the cylindrical surface of the Rhino Fire flywheels for me? Looking again they look a little wider than standard flywheels and may even be Demolisher size anyway. If that's the case then unfortunately that would once again rule out using them or the Workers with Sharks or Rush 39Ks but it would still allow you to use Worker wheels on the standard motors if you do replace the brushes and run a pack (as long as the brushes are definitely the problem). If they are a third, in-between, size then there might be enough bite to allow the Workers to... work. Those couplers wouldn't help (they are meant to join two 2mm shafts together) but the bolt-on hub option would still be a possibility if not an awkward one..

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Mon Jun 05, 2017 1:54 pm View user's profile Send private message
Ratman99UK
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Joined: 04 Apr 2017
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Post Reply with quote
Im at work at the min so i will measure them when i get home, but i already ordered the flywheels, after my last post. No big deal i will upgrade my demolisher if they are not needed.

I removed the resetable fuses already. I also applied voltage directly to the motors (de-soldiered from board) from my bench variable power supply, So im pretty sure the motors are the issue but i will take another look when i take it apart tonight to measure the flywheels.

The couplers, i was thinking of cutting the shaft off of the old motors and using them to lengthen the shafts on the Shark motor by joining them together. (i hope you get what i mean).
Professional Diagram of what im thinking: http://i.imgur.com/MnYjGZN.png

OldManNerf
Since your reading this i assume you know i wont be bring this blaster on Saturday anymore. If you still want to run a game with two large guns could you ask JustAJolt to bring one of his vulcans?
Mon Jun 05, 2017 2:20 pm View user's profile Send private message
SSGT
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Post Reply with quote
Those couplings tend to be around 20mm long and will be too long to fit between the motor and the flywheel the way it's normally mounted without moving the flywheel too far off-axis and mucking up the alignment with the barrels. You have given me an idea though as it might be possible to mount the flywheel the other way around (as per conventional flywheel setups) as per fig.3 below.



As standard, the Rhino Fire flywheels are pressed onto the shaft such that about 5mm of shaft is exposed. If the Rhino Fire does use Demolisher-width flywheels then there's not much in the way of wiggle room as the darts are already contacting near the very edge of an already very wide flywheel. A shorter shaft motor might work but it's unlikely as you'll be losing almost half the contact area. If you instead extend the shaft with a coupling, and mount the standard flywheels backwards, then you should be able ensure a good fit on the shaft. The only thing you might have to do is cut a hole for the shaft/flywheel hubs to fit through and you wouldn't be able to use Demolisher Worker wheels with this setup as the concave contact area would be too far inboard (you could, however, use standard Worker/Artifact etc. flywheels with this setup). Since you now have three interfaces between the motor shaft and the flywheel, presenting two additional points of relative movement, it'd also be a very good idea to grind flats onto the two sections of shaft that the coupling attaches to (if you don't want to risk damaging the motor then, at the very least, you should grind a flat onto the shaft between the coupling and flywheel). Since the flywheel overlaps the coupling you would have to tighten down that grub screw before pressing the flywheel onto the shaft - not too big of a deal and on the plus side, if you fit a few flywheels with couplings, it'd make swapping flywheels ridiculously easy. You are adding mass to the axle but, since it's relatively close to the centre, it shouldn't affect the moment of inertia/spin-up times too badly.

I wouldn't cannibalise the old motors for shafts. You might need them later and you wouldn't be able to salvage enough shaft from them anyway (you'd need about 25mm for each side of each motor). You can buy 2.0mm axles/shafts fairly cheaply anyway (go for steel rather than aluminium).

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Last edited by SSGT on Mon Jun 05, 2017 5:22 pm; edited 1 time in total
Mon Jun 05, 2017 3:41 pm View user's profile Send private message
Ratman99UK
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Post Reply with quote
The flywheels are the same as a stryfe:
https://goo.gl/photos/VZaNKDdNm7iuiKWt8
https://goo.gl/photos/GdeJtgchX86YxYa5A

So the demolisher flywheels idea is still looking good Wink

Just going to have dinner and I will upload a YouTube video of the motors so you can see the speed both on the lipo and directly connected to my power supply.

---edit----

these are photos of the brushes and motor:
https://goo.gl/photos/m7pqqDBh33JxM4mLA

and here is a video of the flywheels running on a 2s followed by the motor receving 9v (stock voltage) direct from power supply. I also cleaned the brushes with IPA and then did the same. before cleaning it was drawing 3 amp and afterwards it was drawing 2 amp. I dont know if thats good or bad, im assuming its good as the motor isnt having to pull as much power to spin up.

https://youtu.be/2BGTcWtbQ_0

Ratman99uk



Ratman99UK
Mon Jun 05, 2017 5:04 pm View user's profile Send private message
SSGT
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Post Reply with quote
The lower current draw implies either a reduction in friction, and therefore less load on the motors (even at "no-load" the motor has to overcome the frictional load of the bearings, brushes and air resistance), or an increase in resistance (V=I*R - higher resistance means lower current for a given voltage across something). Based on the pitch of the motor whine it sounds like the motors are spinning slower after having the brushes cleaned which implies the latter although I couldn't suggest why unless some residue was left on the brushes/commutator or the copper began to oxidise. I wouldn't worry about it too much if the brushes and/or motors are going in the bin at some point anyway.

That's good news on the flywheels though. That should mean that Demolisher wheels have a good chance of working with shorter shaft motors the only potential worry there is that it will likely increase the moment load on the flywheel hub (since it'll meet the motor shaft further away from the point of contact with the darts). Even if that is an issue it shouldn't be the end of the world as the coupling/reversed flywheel idea should still be an option.

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Mon Jun 05, 2017 6:51 pm View user's profile Send private message
Ratman99UK
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Post Reply with quote
Its finished!

The flywheels fit perfect and the blaster is a beast.

The fitted flywheels: https://goo.gl/photos/cJ35QiNx2szosgn67

and a video of it firing on a 3s in my garden:

https://youtu.be/GRMiSlRg_CA

Thanks so much for the input SSGT, if your comming to BoB let me know and I will bring it with me for you to take a look at.

Ratman99UK
Mon Jun 19, 2017 7:23 pm View user's profile Send private message
tbr
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Post Reply with quote
Good to see you got it working well! That's looking really nice now Smile

I got hold of one of these last year, all the motors seemed a bit iffy and would rarely spin up, thinking it was a loose wire or something I opened it up....

(at this point I'd only messed around with a Stryfe)

.... saw the mass of wires all over the place and prompty put it back together and put it all in a plastic bag to "Look at another day".
Tue Jun 20, 2017 8:25 am View user's profile Send private message Send e-mail
SSGT
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Post Reply with quote
No worries. The perspective makes it hard to see but, comparing your setup to the image of the standard layout from the nerfarmourer blog, you might need to move the flywheels inboard a bit to centre the contact profile of the flywheels with the barrels which will probably mean cutting away some of the plastic behind the flywheels. I don't think there's anything behind there that will prevent you from removing a few mm of material (I asume it's mostly there to prevent darts working their way up behind the flywheels and causing a major stoppage) but have a good look beforehand. If removing material weakens the assembly a bit too much you should be able to bond in pieces of ABS to fill the gaps fairly easily.

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Antonius wrote:
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Mon Jun 26, 2017 5:18 pm View user's profile Send private message
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