Newbie ROSSA project

[ajlovering]

Hi

 

You will have to increase the pinion on the clutch bell as you wont be able to engage the teeth of the gears. The best would be to use a 32/32 pinion spur to get the distance to enable the gears to engage. 

 

The quoted BHP for that engine is way off. A decent .28 engine will give about 1.2 hp if you are lucky

 

Cheers

 

 

[m1tch_87]

6 minutes ago, ajlovering said:

Hi

 

You will have to increase the pinion on the clutch bell as you wont be able to engage the teeth of the gears. The best would be to use a 32/32 pinion spur to get the distance to enable the gears to engage. 

 

The quoted BHP for that engine is way off. A decent .28 engine will give about 1.2 hp if you are lucky

 

Cheers

 

 

 

I have run the numbers and unfortunately due to the gearing on the box if I ran a 1:1 setup it would top out at 74mph in 2nd gear, I will need to run with a larger clutch bell vs the spur gear, I have the largest clutch bell I can find which is the 23T. The HPI Savage setup has the engine and box inline with each other and there is a platform which the engine sits on which runs above the drive to the rear to get the correct gear mesh.

 

I am going to be running the engine offset as it is in the stock FTX setup and will be laying the box down, I can simply increase the height of the engine slightly to mesh correctly with the gears. Its a shame that the box has quite a reduction on it but I guess it would be needed to be able to have the 2 gears as an off the shelf option, I could always run a layshaft if needed though - will look into how everything is put together.

 

I will be running the larger .28 engine on the car soon for break in and will use the single 50t spur gear as standard initially - can then increase from the 14t to 18t and then swap it out for a 23t clutch bell gear but still using the 50t single gear for practice - this will top out at just over 50mph.

 

I will get some photos up of the ideas and setup I currently have, its probably easier to explain, I will also check out other option parts for the 2 speed box or indeed the 3 speed box - might be able to add some better gearing in the transmission so I don't need to go so wild with the clutch and spur on the input shaft.

[m1tch_87]

Here is the engine sitting in the stock position in the current chassis, you can see its basically 1 set of holes out - although the holes are for the adjustable runners) will be fairly simple to sort the engine mounts out as they are adjustable, the gearing meshes fine as well on the single gear:

 

 

Here is the HPI 2 speed box on its side, the driveline is still running central and as its on its side the clutch bell can mesh with the gear which will be attached onto the input shaft.

 

 

Top down view of the setup with a spare dogbone (wrong size) showing how the setup will go - I need to extend the chassis by the length of the transmission:

 

[ajlovering]

there is no limit to the size of pinions you can use. this is 36T

Edited February 29, 2016 by ajlovering

[m1tch_87]

8 hours ago, ajlovering said:

there is no limit to the size of pinions you can use. this is 36T

 

Where did you get that? Or did you make it to fit? I can only find up to 23t threaded gears for the clutch bells, I think I found that I can import a 30t clutch bell from the states - I would love to be able to run a much larger clutch bell as it means that its easier to sort out the other gears etc. Is that an unthreaded spur gear locked down by the red gear at the front?

[ajlovering]

Almost all threaded pinions and clutch bells use a 12mm 0.5 pitch thread. You can buy the taps online and also the gears. Just drill out to 11.5 mm and thread the gears

 

http://www.ebay.com/itm/MUGEN-SEIKI-RC-PRIME-12-THREADED-CLUTCH-BELL-K0241-NIP-/121792378689

 

Cheers

[m1tch_87]

1 hour ago, ajlovering said:

Almost all threaded pinions and clutch bells use a 12mm 0.5 pitch thread. You can buy the taps online and also the gears. Just drill out to 11.5 mm and thread the gears

 

http://www.ebay.com/itm/MUGEN-SEIKI-RC-PRIME-12-THREADED-CLUTCH-BELL-K0241-NIP-/121792378689

 

Cheers

Thanks for that, I did check the threads on a thread gauge on the current threaded clutch bell and I am glad you confirmed the specs, will get a tap and then work out what gearing I want to go with, then hunt down a spur gear to use.

[ajlovering]

HPC gears

[m1tch_87]

Slight update, I have now managed to get the flywheel and clutch onto the engine, its running the standard 14t clutch bell for break in, I took the pull starter off which promptly exploded so I am going to have to get a different starting device, tempted by the rotostart but I know the bump start would be better option for racing.

 

The FTX Vantage body turned up as well, I can't use it though as its too narrow - thought that the Carnage and Vantage used the same chassis plate but apparently not, the aluminium arrived as well so I can extend the chassis to fit the gearbox.

 

I am still looking into gearing options as I know that I can get a 44/39 2 speed gearbox using external gears but would require rather large gears to be added to the clutch bell which might be do-able with the threaded clutch bell.

 

An issue I have found is that the engine shaft isn't long enough for the threaded 2 speed clutch bell, I am guessing there is an extension piece you can get to run the longer 2 speed clutch bells out there?

 

I also bought a few pinions to try out with the stock setup, they were the 48dp ones - it seems that the FTX has mod 1 parts as standard as the pinion is very small in terms of tooth size and won't mesh with anything.

 

I have also replaced the lower A arm that was broken so the car is ready to roll again with the stock engine - will have a go with that soon when I have some spare time, it also means that I have a spare .18 engine which I could perhaps look to use to create another car perhaps a dragster to go after the small block IC record as well but will initially just use it for practice.

 

Just deciding if I want to go for a bump start or rotostart on the engine.

[m1tch_87]

I have purchased a blacking plate for the back of this engine, will be fitting it when it arrives and will be going for a starting box, I took the time this evening to check the possible fitment and positioning of the box and engine. The plan will be to extend the chassis slightly at the rear and also raise the front and rear suspension to be inline with the output shafts of the larger gearbox, the fuel tank will be smaller, I have also just loosely placed the wheels, box and engine in to just show a possible layout:

 

 

 

I am still quite tempted to look into using the stock 2 speed option though but running a layshaft along side, saying that, the engine might be able to pull the single gear due to the much lighter chassis and more powerful engine.

 

I am quite tempted to look at a few other options, especially looking at using the stock 2 speed upgrade and simply run 2 larger gears on the clutch bell (I have the tap coming soon for threading).

 

I have found that you can also get a 44/39 2 speed setup, although for the FTX its a 50/45 - a 45/45 gearing on the 2 speed box would yield a 112mph theoretical top speed. It would mean I would need a 40/45 gearing on the clutchbell.

 

This would then pull the car to around 90mph in 1st using the 40/50 combo, then to the 112mph using a 45/45 2nd gear @ 28,000 rpm.

 

I would also have a spare small block engine and could even look into building something up using the 2 speed HPI gearbox as a rear diff as a dragster if I decide not to go with the HPI box - to be honest its much larger than I expected!

 

I will think through some options but the 2 speed external gearing might be useful as it would mean that I wouldn't need to try and fit a larger gearbox in as the .28 engine fits fine in the stock location.

Edited March 3, 2016 by m1tch_87

[m1tch_87]

I am also looking into other body ideas, I won't be running the suspension in the stock location - will be attaching the m3 rods to the front of the diffs to drop the ride height etc, I am therefore looking into some of the 190mm bodyshells which should fit the rest of the chassis but have the wheels still open on each side. This should allow a low drag body but still be able to run open wheel class, I am still looking into other body options, I would need to cut a hole for the nitro engine heatsink.

 

If I get a raw 190mm 1/10 body shell without the wheel arches cut out I can then add in the holes/slots for the steering arms and and A arms to keep the body as streamlined as possible.

 

I am planning to buy the 2 speed bolt on optional upgrade and then increase the clutch bell gearing up to increase the top end - this will maintain the stock setup and footprint but allow for easier mods.

 

Here is the plan for the changes:

 

• Change the engine to the .28 using an additional set of engine mount slots
• Change the 1 speed box to a 2 speed option box running 45/50 spur gears as standard
• Run much larger pinion gears on the clutch bell - aiming for basically 40/45 clutch bells to give a 40/50 first gear and a 45/45 second gear with stock front and rear diff ratios
• Replace the shocks with m3 threaded bar and eyelets to drop the ride height suspension will be via the tyres
• Bolt on the 1/8 wheels and onroad tyres using the 17mm hex wheel adaptors
• Run a low drag 190mm body and cut holes for the steering and suspension linkages
• Cut a hole in the bodyshell for the nitro engine heatsink
• Reduce weight by removing the battery box and front bumper, weight will be reduced by not having the standard shocks anyway plus a weight reduction through wheels and tyres

The above setup should give me the simplest setup which theoretically would give me a good top end, due to it being a 1/10 scale car gives it a lighter weight and so therefore the acceleration would be better. The gearing is fairly tall, the engine might also rev up higher than 28,000 as I believe the HPI 4.6 engine revs to 35,000 so I have gone with the lower side of the RPMs. I have also not taken into consideration any tyre ballooning which will further gear up everything although the on road tyres are low profile.

[Ben Willis]

Just a word of warning on the aero/ride height. If you're running the car that low to the ground you will generate more lift than downforce, especially with an off the shelf body. It may sound counter intuitive, but you want airflow under the car... As the air goes over the top of the body it attempts to push the same amount of air mass through a smaller space since there is an obstacle in the way, therefore to maintain the same mass flow the velocity of the air close to the car (in what's known as the boundary layer) will increase significantly. The absolute pressure of the air is a function of velocity whereby as velocity increases the pressure decreases, thus a significant amount of lift will be produced over the top of the car. Running a higher ride height will allow air to pass under the car, splitting the air and creating a low pressure area under the car (producing more downforce) by the same theory as I just explained, but it also reduces the amount of air being sped up over the top the car since it is being split. Now, I'm not saying jack it up meters into the air, but running it as low as in those pictures will likely make it very unstable, particularly at high speed... just a word of warning

[m1tch_87]

4 hours ago, Ben Willis said:

Just a word of warning on the aero/ride height. If you're running the car that low to the ground you will generate more lift than downforce, especially with an off the shelf body. It may sound counter intuitive, but you want airflow under the car... As the air goes over the top of the body it attempts to push the same amount of air mass through a smaller space since there is an obstacle in the way, therefore to maintain the same mass flow the velocity of the air close to the car (in what's known as the boundary layer) will increase significantly. The absolute pressure of the air is a function of velocity whereby as velocity increases the pressure decreases, thus a significant amount of lift will be produced over the top of the car. Running a higher ride height will allow air to pass under the car, splitting the air and creating a low pressure area under the car (producing more downforce) by the same theory as I just explained, but it also reduces the amount of air being sped up over the top the car since it is being split. Now, I'm not saying jack it up meters into the air, but running it as low as in those pictures will likely make it very unstable, particularly at high speed... just a word of warning

 

I am going to check different ride heights, although I am going to be going as low as possible to get some ground effect, eg the lower the car the more its stuck to the road hence the F1 cars with the skirts in the 80s to keep the air under the car. I can't get my head around how the airflow would work in your scenario - the faster air flow under the car would decrease the air pressure bring the car down.

[m1tch_87]

I have now ordered the 12mm tap and the 40t and 45t gears, the 2 speed box should be arriving soon, I have also test fitted the 1/10 to 1/8 wheel adaptors however the wheel threads aren't quite long enough so have gone with another adaptor which should work fine.

 

Still deciding on a bodystyle, need to get some time working on driving the car with the stock engine - will see if I am able to run it around a bit on Friday on a day off, I also have a starter box coming as well so that will make even the pull start .18 engine easier to get running.

[Ben Willis]

In order to get the faster airflow under the car to work properly you will need more airflow under the car. Running that low you won't get enough airflow underneath the car... If you want to run the car really low you will need a splitter, a very smooth, flat underbody, you will need to run some rake and most likely some kind of diffuser at the rear to pump enough air under the car and get the effect of the low pressure area underneath

[m1tch_87]

4 hours ago, Ben Willis said:

In order to get the faster airflow under the car to work properly you will need more airflow under the car. Running that low you won't get enough airflow underneath the car... If you want to run the car really low you will need a splitter, a very smooth, flat underbody, you will need to run some rake and most likely some kind of diffuser at the rear to pump enough air under the car and get the effect of the low pressure area underneath

 

I will be running a front splitter, the car has a flat chassis, will be looking at rear diffusers and the car will be raked (with fixed suspension), will probably also look at running some air guides down each side to keep the air under the car and away from the wheels (as the car will be open wheel).

 

I'm just going on the other speed run cars I have seen with regards to ride height etc:

 

Edited March 8, 2016 by m1tch_87

[Ben Willis]

Ahh, okay, sorry, I just got the impression you were gonna slam it and do nothing else, my apologies :b

[Ben Willis]

Ahh, okay, sorry, I just got the impression you were gonna slam it and do nothing else, my apologies :b

[m1tch_87]

49 minutes ago, Ben Willis said:

Ahh, okay, sorry, I just got the impression you were gonna slam it and do nothing else, my apologies :b

 

Slamming it is part of it lol but I am still working on the aero work at the moment, I don't have a vac former so I am seeing what bodies might fit along with the additional extras under the car.

[m1tch_87]

I'm going to bin the threaded clutch bell, I don't know if its a second or something but it doesn't seem right, will look to spend a bit more get a branded threaded clutch bell.

[m1tch_87]

Just working on bodyshell thoughts and looking at some of the Rustler builds I think I might be able to get away with a stock truggy shell with a few mods on it, the issues that the Rustlers have is the fact that its RWD with no weight on the front so they usually flip as the air catches the shell. The FTX has its engine in the middle/rear so will still need some aero at the front to keep the nose down although I do plan to rake the chassis slightly.

 

Using the stock body I have had a look at how things could be improved, the stock front bumper has been removed which gives a perfect location for a front wing or some sort, I have used a bit of tape to also show how I would bring the front of the bodyshell down to the chassis (its cut out due to the stock front bumper).

 

Here is the car on the lowest suspension setting with the 1/8 wheels and stock body to show how it could look overall:

 

 

Quick mock up adding in some tape etc to the front:

 

 

You can however see how this shell would also get caught in the air flow via the front wings, I would look to cut slots in the shell and not cut out the wheel arches fully so that minimal air can get caught under the chassis:

 

 

Same with the rear of the shell - due to nothing at the back needing to move as there isn't any steering it would be almost entirely covered.

 

 

With regards to the engine, I will look to fit a small side duct and then open up the whole rear of the shell as well as extend the rear slightly, I would also add on some vertical lexan on each side of the chassis on the back to give it stability.

[m1tch_87]

Hmm might have to put this project on hold, just trying to have a practice around in the back garden, so far I have spent around half an hour to get the thing running, total run time so far with the stock engine is around 20 seconds or so. Tempted to just go electric and be done with it, I can see why nitro cars are on their way out in terms of popularity.

[m1tch_87]

The HPI clutch bell arrived, fits perfectly and I also have a shim kit so I can now fine tune the clutch bell and end float.

 

I do now have a starter box however I need a fair bit of time to get it setup correctly though as its not really fitting the FTX chassis very well.

 

Next steps for this project are:

 

• Learn more about nitro engine tuning to get some time actually running the thing in stock form
• Look to add the 2 speed gearbox onto the stock .18 engine first and run the 18/23 clutch bell
• Make the rigid suspension as the eyelets have now arrived as well as the m3 threaded bar
• Trial fit the larger 1/8 wheels as the hub adaptors have arrived - hopefully these will actually work now!
• Look to get a new body/mod the current damaged one
• Look at front lip splitters and diffusers
• Fit the engine mounts to fit the larger engine

[locky]

On 03/03/2016 at 07:56, m1tch_87 said:

I am still looking into gearing options as I know that I can get a 44/39 2 speed gearbox using external gears but would require rather large gears to be added to the clutch bell which might be do-able with the threaded clutch bell.

 

Have you looked at the 3 speed upgrade to the 2 speed with high speed third gear ratio? In theory it should give you a few more mph.

[m1tch_87]

21 hours ago, locky said:

 

Have you looked at the 3 speed upgrade to the 2 speed with high speed third gear ratio? In theory it should give you a few more mph.

 

I have indeed, its why I have the 2 speed box as I know there is the upgrade path to 3 speed, I am however initially going to go with the 2 speed upgrade with the external gears as the HPI box adds in another set of gear reductions on top of the front and rear diffs. Due to the HPI Savage gearbox is kinda meant for lower speed higher torque running I don't know how well it will hold up with the input shaft being spun at higher RPMs. To get the gearing right with that box I would need a larger clutch bell and smaller spur on the input shaft of the box - so the input shaft will be spinning faster than the engine.

 

It is still an option though and I am also tempted to try and use it with the .18 engine that is coming off the stock chassis and perhaps run the output shaft of that gearbox directly to the rear wheels like a dragster. I am going with simplicity to start with by keeping the car almost stock in terms of layout but adding a bigger engine and more teeth on the clutch bell to gear it up.